(BQ) Part 1 book “Pediatric bone biology & diseases” has contents: Pediatric bone histomorphometry, a diagnostic approach to skeletal dysplasias, the spectrum of pediatric osteoporosis, osteogenesis imperfecta, sclerosing bone dysplasias,… and other contents.
C H A P T E R 16 Pediatric Bone Histomorphometry Frank Rauch Shriners Hospital for Children, Montreal, Quebec, Canada INTRODUCTION Bone biopsies can be useful for establishing a diagnosis in an individual patient with a bone disorder They can also be used for investigating disease characteristics or treatment effects Biopsy samples can be assessed qualitatively or quantitatively The quantitative analysis of bone specimens is called bone histomorphometry Bone histomorphometry is a key tool for studying bone tissue Both the activity of bone metabolism and the amount and distribution of bone tissue can be analyzed with unsurpassed resolution When tetracycline labeling is performed prior to biopsy, bone histomorphometry offers the unique possibility to study bone cell function in vivo Importantly for pediatric use, the growth process does not directly interfere with the measurements Bone histomorphometry is also an excellent educational tool The insight derived from studying bone tissue can be used better to understand results of indirect methods, such as bone densitometry or biochemical markers of bone metabolism Knowledge of bone tissue is crucial to put the disparate findings of molecular and cellular studies into perspective Despite these advantages, bone histomorphometry is underused in pediatrics This may be partly due to the fact that histomorphometry requires an invasive procedure to obtain a bone sample, is labor intensive, and needs special equipment and expertise Other reasons may include overestimation of the utility of non-invasive bone diagnostics and lack of information about what bone histomorphometry does Bone tissue is very hard and for that reason is more difficult to process than soft tissues In routine pathology, bone tissue is therefore usually decalcified and thus converted into a soft tissue However, this leads to the loss of important information about bone mineralization and bone cell activity To assess metabolic Pediatric Bone, Second Edition DOI: 10.1016/B978-0-12-382040-2.10016-4 bone disorders, it is therefore generally more informative to analyse samples undecalcified This chapter summarizes the methodology of bone histomorphometry and highlights the tissue-level characteristics of normal and abnormal bone development The aim is to open this field to the non-specialized reader with an interest in pediatric bone disorders More detailed accounts of methodology can be found elsewhere [1,2] BASIC CONCEPTS Between birth and adulthood, bones undergo considerable increases in size The most frequently assessed aspect of this process is longitudinal bone growth, as reflected by body height The increase in bone length is mostly due a mechanism called endochondral ossification [3] The primary effector cells of this process are growth plate chondrocytes These cells continuously divide and synthesize a cartilaginous matrix which, in a stepwise process, is subsequently converted into osseous tissue Longitudinal bone growth and endochondral ossification are a traditional focus of interest in pediatric research However, histomorphometry does not usually deal with endochondral ossification and therefore this process is not described in more detail here Bone histomorphometry mostly provides information on two other aspects of bone development, bone remodeling and bone modeling These tissue-based mechanisms of bone development and maintenance have received far less attention in pediatrics than longitudinal bone growth Bone created by endochondral ossification is continuously renewed by a process named remodeling [4] Remodeling consists of successive cycles of bone resorption and formation on the same bone surface The basic features of this process are identical for trabecular and cortical bone [4] A group of osteoclasts removes a small quantity (“packet”) of bone tissue 383 Copyright Ó 2012 Elsevier Inc All rights reserved 384 16 PEDIATRIC BONE HISTOMORPHOMETRY which, after a reversal phase, is replaced by a team of osteoblasts The entire group of cells involved in this process is named remodeling unit or basic multicellular unit The fact that osteoblast activity is linked to previous osteoclast action has been named “coupling” [4] The difference in the amounts of bone which are removed and added in one remodeling cycle is called “remodeling balance” The remodeling balance is typically close to zero so that there is no or little net effect on the amount of bone However, the remodeling process renews the bone tissue and thereby prevents tissue damage from accumulating [5] Bone growth in width occurs through a different mechanism, called modeling [4] Bone modeling involves the same set of effector cells as bone remodeling, osteoclasts and osteoblasts However, while in remodeling both cells types are sequentially active on the same bone surface, osteoclasts and osteoblasts act on different surfaces during modeling During bone growth in width, osteoblasts are typically located on the outer (periosteal) surface of a bone cortex, where they deposit bone matrix and later mineralize it Thereby, the outer circumference of a long bone or a vertebral body is increased At the same time, osteoclasts located on the inner (endocortical) surface of the cortex resorb bone, thus increasing the size of the marrow cavity Since osteoblasts are active without interruption in bone modeling, much more rapid increases in the amount of bone tissue can occur than in bone remodeling Osteoclasts usually remove less bone tissue than is deposited by osteoblasts during modeling [4] Therefore, modeling leads to a net increase in the amount of bone tissue For example, the difference between osteoblastic matrix deposition and osteoclastic bone resorption leads to cortical thickening Modeling and remodeling are not just abstract concepts of bone metabolism, but are reflected in the histoanatomy of cortical bone that the transiliac sample must be obtained under standardized conditions and with appropriate tools It is essential that the sample is not fractured or crushed and contains two cortices separated by a trabecular compartment These requirements are often quite difficult to meet in small or very osteopenic children Bone specimens for histomorphometric evaluation are horizontal, full-thickness (transfixing) biopsies of the ilium from a site cm posterior from the anterior superior iliac spine (Fig 16.1) This bone is easily accessible, does not require extensive surgery, and is associated with few postoperative complications Also, this is the only site for which pediatric histomorphometric reference data have been published [6] It is important to note that horizontal transiliac samples are required for histomorphometric evaluation Vertical samples (from the iliac crest downwards) cannot be used because of the presence of the growth plate The transiliac sample must be obtained at a site well below the iliac crest growth plate Specimens containing growth cartilage not allow for a reliable quantitative analysis because turnover is very high and cortical thickness is very low in the bone adjacent to the growth plate The usual bone biopsy instrument is the Bordier trephine (Fig 16.2) The inner diameter of the trochar should be at least mm We are using mm needles in children below 12 years of age and mm needles in children 12 years or older, unless their height is below the third percentile In children and adolescents, the biopsy procedure is usually performed under general anesthesia This procedure does not have side effects other than transient local discomfort [7] Patients are allowed to get out of bed after hours and can usually be discharged on the same day The operator’s experience is an important factor in obtaining an adequate sample and in keeping intervention-related morbidity to a minimum METHODOLOGY Bone Biopsy Clinical Procedure Bone histomorphometry was first developed to study rib bone samples This was soon abandoned because the ilium proved to be a much more convenient site for obtaining bone samples In principle, histomorphometric analysis can be performed in any bone In clinical pediatrics, however, the utility of samples from sites other than the ilium is limited because reference data are only available for the ilium Quantitative bone histomorphometry requires an intact biopsy specimen of good quality This implies FIGURE 16.1 procedure PEDIATRIC BONE Anatomic location for the transiliac bone biopsy 385 METHODOLOGY FIGURE 16.2 View of a 5-mm trephine for transiliac bone biopsy Full histomorphometric analysis requires prior in vivo bone labeling Dynamic parameters of bone cell function can only be measured when the patient has received two courses of tetracycline label prior to biopsy Tetracycline compounds form calcium chelate complexes that bind to bone surfaces These complexes are buried within the bone at sites of active bone formation, whereas they redissociate from the other bone surfaces once serum tetracycline levels decrease The tetracycline trapped at formation sites can then be visualized under fluorescent light Figure 16.3 shows the labeling schedule The tetracycline compound used is tetracycline-HCl (brand names differ from country to country, e.g TetracyclineÒ; SumycinÒ, AchromycinÒ, and several other brand names) at a dose of 20 mg/kg body weight per day, FIGURE 16.3 Schedule for prebiopsy tetracycline labeling PEDIATRIC BONE 386 16 PEDIATRIC BONE HISTOMORPHOMETRY with a maximum dosage of 1500 mg per day The daily amount is given orally in two doses The drug is given for two days in both label courses The two courses are separated by an interlabel time of 10 days Bone biopsy is performed 4e6 days after the last administration of tetracycline Although children and adolescents generally tolerate tetracycline double labeling well, some side effects might be observed, such as allergic reactions, vomiting, and photosensitivity Administering the drug after meals can diminish gastrointestinal side effects It is important that these meals not include milk or other dairy products because tetracycline complexes with calcium contained in the food and is not absorbed adequately Sun exposure must be avoided while taking tetracyclines Tetracycline use is generally not recommended for children younger than years of age because discoloration of teeth may occur However, the previously mentioned schedule appears to be safe in this respect At the Montreal Shriners Hospital, it has been used for more than 300 biopsies in children younger than years of age and tooth discoloration has never been observed Sample Processing The biopsy sample should be placed into a fixative as soon as possible after the procedure The fixation process aims at the preservation of bone tissue constituents by inactivating lysosomal enzymes The choice of fixative and temperature at which the sample should be kept depends on the planned staining techniques For routine histomorphometry, 70% ethanol or 10% buffered formalin at room temperature can be used The duration of fixation should be at least 48 hours but should not exceed 10 days because the tetracycline labels are washed out when fixation is too long Following fixation, the specimen is dehydrated in absolute ethanol and embedded in methylmethacrylate Cutting mineralized bone requires a special microtome For each specimen, two to five series of undecalcified, 6e10-mm-thick consecutive sections should be cut at least 150 mm apart The sections are then deplastified to allow for optimal staining The most widely used staining methods for histomorphometric analysis are toluidine blue and Masson Goldner trichrome The sections that will be used for fluorescence microscopy are mounted unstained An appropriately large sample area must be available to obtain representative measures Therefore, at least two sections of a biopsy should be available for each type of analysis in order to obtain a measurable tissue area of 40e50 mm2 Measurement Procedure The actual histomorphometric analysis requires a high-quality microscope that is suitable for fluorescence microscopy In the early years of the technique, histomorphometric measurements were performed by manual or point-counting techniques These methods involved the use of a grid placed in the microscope eyepiece This has been replaced by computerized systems that allow for automation of the analysis process Whatever method is used, histomorphometric analysis is time consuming because even the most advanced systems rely on the operator’s judgment to identify correctly the individual histoanatomical components HISTOMORPHOMETRIC MEASURES Definitions Histomorphometric measures follow a standardized and well-defined terminology that was introduced in 1987 [8] Articles published before that time are often quite difficult to read because many authors used private nomenclature An introductory overview of the most important histomorphometric terms is given here More detailed information can be found in the 1987 terminology report [8] In histomorphometry, bone is defined as bone matrix, whether mineralized or not Unmineralized bone is called osteoid, whereas mineralized bone does not have a special designation Bone and the associated soft tissue, such as bone marrow, are referred to as tissue Osteoblasts are cells on bone surfaces that are producing and secreting bone matrix currently Flat cells of the osteoblast lineage that cover quiescent nonperiosteal bone surfaces are referred to as lining cells The term osteoclast is restricted to multinucleated cells that are currently in contact with a bone surface and are actively resorbing bone A transiliac biopsy specimen consists of two cortices separated by a cancellous compartment (Fig 16.4) The terms cancellous and trabecular are usually used interchangeably The outer delimitation of the cortex is called the periosteal surface, and the inner border is the endocortical surface (Fig 16.4) Osteonal and Volkmann canals are lined with intracortical surfaces The bone surfaces in the cancellous compartment are referred to as cancellous (or trabecular) surfaces Intracortical, endocortical, and trabecular surfaces are in continuity and together form the endosteal surface or envelop In the literature, there is confusion regarding the latter term because many authors use the term endosteal surface when in fact referring to the endocortical surface Histomorphometric measurements are performed in two-dimensional sections This may cause conceptual problems because bone is a three-dimensional organ What is perceived and measured as an area in the PEDIATRIC BONE 387 HISTOMORPHOMETRIC MEASURES FIGURE 16.4 Schematic representation of a bone biopsy section The different types of bone surfaces are indicated histologic section in fact reflects a volume In order to highlight the three-dimensional nature of bone, threedimensional terminology is favored when reporting histomorphometric results For example, the percentage of unmineralized bone is measured in the two-dimensional bone slice as osteoid area relative to total bone area However, the result of this ratio is reported as osteoid volume per bone volume This is done simply by convention, and it should not be mistaken as an actual three-dimensional measurement Histomorphometric Parameters Terminology for most histomorphometric parameters follows a standardized scheme: source e measurement/ referent Source refers to the type of bone that is measured (e.g cancellous or cortical) Since analyses are often limited to cancellous bone, the source prefix is usually omitted, as long as there is no possibility of confusion Measurement is the type of parameter that is determined Histomorphometric data are usually not given as absolute values but are related to each other This is what is meant by “referent” Most parameters are related to a surface area or a volume Histomorphometric parameters can be classified into four categories (Table 16.1): structural parameters, static bone formation parameters, dynamic formation parameters, and static bone resorption parameters Dynamic parameters can only be determined when tetracycline labeling is performed prior to obtaining the biopsy There are no dynamic parameters of bone resorption, which is one of the main shortcomings of histomorphometry Structural Parameters The overall size of an intact biopsy specimen is expressed as core width (C.Wi) (Fig 16.5), which is the mean distance between the two periosteal surfaces of the sample C.Wi thus reflects the thickness of the ilium, but also depends on the angle between biopsy needle and ileal surface Ideally, the needle should be perpendicular to the ilium, but this is not always easy to achieve Cortical width (Ct.Wi) is determined as the mean distance between the periosteal and endocortical surfaces of each cortex Usually, results from both cortices are combined Determination of Ct.Wi is not as straightforward as the widespread use of this parameter in radiological techniques might suggest Indeed, there is often a smooth transition from cortical to cancellous bone, and two observers may disagree where the border between the two compartments should be drawn Bone volume per tissue volume (BV/TV) of trabecular bone is the combined volume of mineralized and unmineralized bone matrix relative to the total volume of the trabecular compartment (see Fig 16.5) BV/TV can also be measured in cortical bone, but many authors prefer to express cortical results as cortical porosity (Ct.Po), which is simply the complement of BV/TV in cortical bone (Ct.Po ¼ 100% À BV/TV) The two surface-to-volume ratios (BS/BV and BS/TV) are important for establishing the link between bone surfacebased cellular activity and the effect on the amount of bone For example, the differences in turnover of cortical and cancellous bone mostly reflect differences in the bone surface-to-volume ratio, whereas the surfacerelated activity of bone cells is quite similar [9] In trabecular bone, BV/TV can be schematically divided into two separate components: mean trabecular thickness (Tb.Th) and trabecular number (Tb.N) Tb.N is equivalent to the number of trabeculae that a line through the cancellous compartment would contact per millimeter length The mean distance between two trabeculae, trabecular spacing (Tb.Sp) or trabecular PEDIATRIC BONE 388 TABLE 16.1 16 PEDIATRIC BONE HISTOMORPHOMETRY The Most Commonly used Histomorphometric Parameters Parameter Abbreviation Structural parameters Core width C.Wi Cortical width Ct.Wi Cortical porosity Ct.Po Bone volume/tissue volume BV/TV Trabecular thickness Tb.Th Trabecular number Tb.N Trabecular separation Tb.Sp Static formation parameters FIGURE 16.5 Basic histomorphometric parameters of bone Osteoid thickness O.Th Osteoid surface/bone surface OS/BS Osteoid volume/bone volume OV/BV Osteoblast surface/bone surface Ob.S/BS Osteoblast surface/osteoid surface Ob.S/OS Wall thickness W.Th structure from a single two-dimensional section In any case, analysis of trabecular bone architecture has not been applied to pediatric histomorphometry Static Formation Parameters Dynamic formation parameters Mineralizing surface/bone surface MS/BS Mineralizing surface/osteoid surface MS/OS Mineral apposition rate MAR Adjusted apposition rate Aj.AR Mineralization lag time Mlt Osteoid maturation time Omt Bone formation rate/bone surface BFR/BS Bone formation rate/bone volume BFR/BV Activation frequency Ac.f Formation period FP Static resorption parameters Eroded surface/bone surface ES/BS Osteoclast surface/bone surface Oc.S/BS Number of osteoclasts/bone perimeter N.Oc/B.Pm separation, can be mathematically derived from Tb.Th and Tb.N This parameter is often included in histomorphometric reports, although it does not provide any additional information once Tb.Th and Tb.N are known Apart from these classic structural parameters, a set of indices has been developed to describe quantitatively the architecture of trabecular bone [10] These approaches are limited by the fact that the three-dimensional architecture of a bone cannot be reconstructed Osteoid surface per bone surface (OS/BS) is the surface of all the osteoid seams in the cancellous compartment relative to the total surface of trabecular bone (Fig 16.6) Osteoid thickness (O.Th) corresponds to the mean distance between the surface of the osteoid seam facing the bone marrow on the one hand and the interface between unmineralized and mineralized bone on the other (Fig 16.6) This interface is called the mineralization front, because mineral is rapidly incorporated into the organic bone matrix at that location Osteoid seams not end abruptly, so some minimum width must be specified According to the procedures established at the Montreal Shriners Hospital, osteoid seams above 1.5 mm are included in the analysis [6] Osteoid volume per bone volume (OV/BV) is the amount of unmineralized osteoid relative to the total amount of mineralized and unmineralized bone This value is calculated from OS/BS and O.Th Osteoblast surface per bone surface (Ob.S/BS) is a measure reflecting the area of the interface between osteoblasts and bone relative to the total bone surface During their active life span, osteoblasts become continuously flatter and those that remain on the bone surface turn into lining cells Thus, there is a continuum between flat osteoblasts and lining cells, and it is necessary to indicate the criteria used to distinguish between the two cell types We use a definition of osteoblasts as cells that are directly apposed to osteoid and exhibiting a definite Golgi apparatus Osteoblast surface per osteoid surface (Ob.S/OS) is the percentage of osteoid surface that is covered by PEDIATRIC BONE HISTOMORPHOMETRIC MEASURES 389 FIGURE 16.6 Schematic representation of a remodeling site in trabecular bone Osteoclasts in the front dig a trench across the bone surface, which is then refilled by a team of osteoblasts osteoblasts This value is calculated from Ob.S/BS and OS/BS Wall thickness (W.Th) reflects the amount of bone that is created by the action of a single remodeling unit It is defined as the mean thickness of the bone that has been laid down at a completed remodeling site (i.e at locations that are covered by lining cells and where osteoid production has stopped) (see Fig 16.6) W.Th should not be confused with cortical thickness, with which it does not bear any relationship The confusion can arise when cortices are inappropriately termed cortical walls, as is sometimes done in the radiological literature W.Th is measured as the mean distance between the surface of a trabecula and the cement line The cement line is created in the reversal phase of a remodeling cycle after the osteoclasts have left and before the osteoblasts have arrived (see Fig 16.6), and for this reason it is also called the reversal line Reversal lines only appear during remodeling; thus, they represent a histological criterion to distinguish bone created by remodeling from bone made by modeling [11] The reversal line is difficult to visualize unless special staining procedures are used; alternatively, the wall can be detected by the abrupt change in collagen fiber orientation between adjacent bone lamellae [8] This is usually easily visible under polarized light Dynamic Formation Parameters The dynamic formation parameters yield information on in vivo bone cell function Therefore, these parameters are the key to understanding bone physiology, pathophysiology, and the effect of treatment at the tissue level This underscores the importance of performing tetracycline labeling prior to biopsy Mineralizing surface per bone surface (MS/BS) represents the percentage of bone surface exhibiting mineralizing activity This is usually measured as the total extent of tetracycline double label plus half the extent of single label Mineralizing surface per osteoid surface (MS/OS) is the percentage of osteoid surface undergoing mineralization This is equivalent to the fraction of the osteoid seam life span during which mineralization occurs [8] MS/OS is calculated from MS/BS and OS/BS Mineral apposition rate (MAR) is the distance between the midpoints of the two labels divided by the time between the midpoints of the labeling interval This is one of the most important parameters because it reflects the activity of individual teams of osteoblasts Adjusted apposition rate (Aj.AR) is calculated as the product of MAR and MS/OS As such, it represents the mineral apposition rate averaged over the entire osteoid surface In a steady state of pure remodeling activity and in the absence of osteomalacia, Aj.AR is the best estimate of the mean rate of osteoid apposition [12] because the rate of bone mineralization is identical to the rate of osteoid production under these conditions Mineralization lag time (Mlt) is the average interval between the deposition and mineralization of matrix Mineralization occurs much more rapidly at new formation sites with young osteoblasts than at locations where osteoblasts approach the end of their active careers Mlt therefore represents a value that is averaged over the entire osteoid seam life span Mlt is calculated as the ratio between O.Th and Aj.AR Osteoid maturation time (Omt) is the mean time interval between matrix deposition and the onset of mineralization at a new bone-forming site Omt reflects what is happening at new formation sites when osteoblasts are still “young and dynamic” Therefore, Omt is almost always shorter and never longer than Mlt Omt is calculated as the ratio between O.Th and MAR Bone formation rate per bone surface (BFR/BS) is the volume of mineralized bone formed per unit time and per unit bone surface It is calculated as the product of MAR and MS/BS Since bone metabolism occurs only on the surfaces of bone, expressing bone formation rate relative to bone surface is the most logical approach when hormonal effects on bone remodeling are considered [13] Bone formation rate expressed relative to bone volume (BFR/BV) is equivalent to the bone turnover rate (i.e it indicates the percentage of bone that is turned over per year) This determines the mean age of the bone tissue [9] It is often mistakenly assumed PEDIATRIC BONE 390 16 PEDIATRIC BONE HISTOMORPHOMETRY that a higher bone formation rate is equivalent to a higher accumulation of bone However, remodeling removes approximately as much bone as it forms, and bone formation rate does not give any information about the balance between the two processes It is therefore more appropriate to interpret bone formation rate as an index of bone turnover rate rather than of bone gain The formation period (FP) is the mean time required for building a new bone structural unit or osteon from the cement line back to the bone surface at a single location FP is calculated as the ratio between W.Th and Aj.AR Activation frequency (Ac.f) represents the probability that a new cycle of remodeling will be initiated at any point on the surface by the event of activation Ac.f is the key indicator of remodeling activity It is calculated as the ratio between BFR/BS and W.Th Static Resorption Parameters Eroded surface per bone surface (ES/BS) is defined as the percentage of bone surface presenting a scalloped or ragged appearance at the boneebone marrow interface with or without the presence of osteoclasts This is a controversial measure of bone resorption since there is a high degree of subjectivity in recognizing a surface as “ragged” [14] In addition, many of the locations that are classified as presenting an eroded aspect are the result of aborted resorption attempts rather than of remodeling-linked osteoclast action [14] Osteoclast surface per bone surface (Oc.S/BS) is the percentage of the bone surface that is in contact with osteoclasts Apart from measuring the length of the osteoclastebone surface interface, it is possible to determine the number of osteoclasts Numbers without units are related to two-dimensional referents because the spatial relationships change with cell morphology, and consequently conversion into three-dimensional values is inappropriate [8] The number of osteoclasts per bone perimeter (N.Oc/B.Pm) corresponds to the number of osteoclasts in contact with cancellous bone It is expressed as the number per millimeter length of bone perimeter in a two-dimensional section Osteoclast surface and number are more useful indicators of bone resorption than eroded surface, because their interpretation is less ambiguous However, these are still imperfect indicators of bone resorptive activity, as they reflect only the amount of osteoclasts, but not their function Thus, bone histomorphometry provides far less information on bone resorption than it does on bone formation Reproducibility of Histomorphometric Measures Only one study has evaluated the reproducibility of bone histomorphometric measures in children and adolescents [6] Structural parameters showed a variability of 5e10%, whereas variations were highest for cellular parameters (20e30%) Reproducibility was best for two primary parameters of osteoblast team function e mineral apposition rate and wall thickness (4 and 5%, respectively) The variability of repeated measurements was smaller in children than in adults [15,16], which may be explained by the higher bone turnover in children This effect reduces the sampling error for parameters of bone formation and resorption PEDIATRIC BONE HISTOMORPHOMETRY IN HEALTH AND DISEASE Reference Data for Pediatric Iliac Bone Histomorphometry Reference data have been published based on results from 58 individuals between 1.5 and 22.9 years of age who underwent surgery for reasons independent of abnormalities in bone development and metabolism [6] The results are shown in Table 16.2 Cortical width and cancellous bone volume increase significantly with age, with the latter due to an increase in trabecular thickness Osteoid thickness does not vary significantly with age Bone surface-based indicators of bone formation show an age-dependent decline, reflecting similar changes in activation frequency Mineral apposition rate decreases continuously with age Parameters of bone resorption not vary significantly between age groups In principle, these results can only be used for comparisons if the same methods are used for processing and analyzing the samples Some parameters are more likely to vary with methodology than others Different staining and handling procedures probably least influence measures of bone structure The results for osteoid thickness and osteoid surface extent depend on the cutoff threshold for osteoid width According to the protocol used in the reference data study, all osteoid seams with a width above 1.5 mm are measured If a higher cutoff is used, then higher results for osteoid thickness and lower values for osteoid surface extent will be obtained Wall thickness depends on the type of staining Procedures are available to stain specifically the cement line [17] Wall thickness can then be simply measured as the distance between the cement line and the nearest bone surface In the reference data study, wall thickness was quantified on Goldner stained sections under polarized light as the distance from quiescent bone surfaces to the abrupt change in collagen fiber orientation [18] This method tends to yield higher values than when staining of the cement line is performed PEDIATRIC BONE 391 PEDIATRIC BONE HISTOMORPHOMETRY IN HEALTH AND DISEASE TABLE 16.2 Reference Data (Mean Ỉ SD) for Iliac Bone Histomorphometry from 1.5 to 23 Years Age (years) 1.5e6.9 7.0e10.9 11.0e13.9 14.0e16.9 17.0e22.9 C.Wi (mm) 5.3 Æ 1.4 7.9 Æ 1.7 7.1 Æ 1.8 8.6 Æ 2.4 8.2 Ỉ 1.6 Ct.Wi (mm) 0.70 Ỉ 0.28 0.97 Æ 0.37 0.90 Æ 0.33 1.18 Æ 0.35 1.01 Æ 0.20 BV/TV (%) 17.7 Ỉ 2.6 22.4 Ỉ 4.2 24.4 Æ 4.3 25.7 Æ 5.3 27.8 Æ 4.5 Tb.Th (mm) 101 Ỉ 11 129 Ỉ 17 148 Ỉ 23 157 Æ 22 153 Æ 24 Tb.N (/mm) 1.77 Æ 0.31 1.73 Ỉ 0.17 1.66 Ỉ 0.22 1.63 Ỉ 0.16 1.83 Æ 0.27 Tb.Sp (mm) 481 Æ 112 453 Æ 62 464 Ỉ 78 461 Ỉ 70 404 Ỉ 77 O.Th (mm) 5.8 Ỉ 1.4 5.9 Ỉ 1.1 6.7 Ỉ 1.7 6.3 Ỉ 1.0 6.9 Ỉ 1.2 OS/BS (%) 34 Ỉ 29 Ỉ 13 22 Ỉ 26 Ỉ 17 Ỉ OV/BV (%) 4.0 Ỉ 1.2 2.6 Ỉ 1.0 2.1 Ỉ 1.0 2.2 Ỉ 0.9 1.6 Ỉ 0.7 Ob.S/BS (%) 8.5 Ỉ 4.1 8.2 Ỉ 4.4 6.7 Ỉ 4.5 7.9 Ỉ 4.1 5.3 Ỉ 2.7 Ob.S/OS (%) 26 Æ 14 29 Æ 15 29 Æ 13 31 Æ 12 32 Ỉ 12 W.Th (mm) 33.9 Ỉ 3.8 40.6 Æ 3.0 45.1 Æ 6.9 44.4 Æ 3.2 41.1 Æ 2.5 MS/BS (%) 12.5 Ỉ 4.5 14.9 Ỉ 4.5 11.7 Æ 5.0 12.5 Æ 3.4 7.9 Æ 2.7 MS/OS (%) 38 Ỉ 13 50 Ỉ 22 53 Ỉ 12 52 Æ 14 58 Æ 14 MAR (mm/d) 1.04 Æ 0.17 0.95 Ỉ 0.07 0.87 Ỉ 0.09 0.81 Ỉ 0.09 0.75 Æ 0.09 Aj.AR (mm/d) 0.40 Æ 0.16 0.47 Æ 0.18 0.46 Ỉ 0.10 0.42 Ỉ 0.11 0.43 Ỉ 0.12 Mlt (d) 16.7 Ỉ 6.4 14.1 Ỉ 4.3 14.5 Ỉ 3.0 15.3 Ỉ 3.6 17.3 Ỉ 6.5 5.7 Ỉ 1.3 6.5 Æ 1.0 7.6 Æ 1.8 7.6 Æ 1.2 9.4 Æ 2.3 BFR/BS (mm /mm /y) 48 Ỉ 19 52 Ỉ 16 37 Ỉ 17 37 Ỉ 10 22 Ỉ BFR/BV (%/y) 97 Ỉ 42 78 Ỉ 27 50 Ỉ 21 48 Ỉ 19 29 Ỉ 13 Ac.f (/y) 1.40 Æ 0.53 1.25 Æ 0.37 0.83 Æ 0.35 0.83 Æ 0.27 0.54 Ỉ 0.23 FP (d) 105 Ỉ 18 99 Æ 34 103 Æ 28 114 Æ 32 102 Æ 27 ES/BS (%) 14.8 Ỉ 4.4 17.0 Ỉ 6.0 14.9 Æ 5.6 18.0 Æ 5.7 18.0 Æ 6.1 Oc.S/BS (%) 1.1 Ỉ 0.8 1.3 Ỉ 0.6 0.9 Ỉ 0.4 1.1 Æ 0.7 1.0 Æ 0.4 N.Oc/B.Pm (/mm) 0.35 Æ 0.23 0.36 Ỉ 0.16 0.29 Ỉ 0.14 0.34 Ỉ 0.22 0.31 Æ 0.14 Structural Static formation Dynamic formation Omt (d) Static resorption Cellular parameters depend on the degree of cellular preservation, which is influenced by sample fixation and staining technique In the reference data study, biopsy specimens were fixed in 10% phosphate-buffered formalin (pH 7.1) and kept at room temperature for 48e72 hours They were then dehydrated in increasing concentrations of ethanol, cleared with xylene and embedded in methylmethacrylate After sectioning, samples were deplastified with ethylene glycol monoethyl acetate to allow for optimal staining Measurements of cells were performed using toluidine stained sections Mineralizing surface and mineral apposition rate vary with the labeling substance, labeling schedule, and dosage used [19] The labeling schedule in use at the Shriners Hospital for Children in Montreal is shown in Figure 16.3 As mentioned earlier, eroded surface is a subjective measure [14] In the reference data study, eroded surface was measured in toluidine-stained sections Bone surfaces with scalloped or ragged appearance of the boneebone marrow interface are included, whether or not osteoclasts are present This includes also shallow PEDIATRIC BONE 392 16 PEDIATRIC BONE HISTOMORPHOMETRY excavations, which are identified by the presence of eroded lamellae at the bone surface Development of Human Bone Tissue A histomorphometric study on the proximal femoral metaphysis of 35 fetuses and newborns showed that trabecular bone volume increased between the second and third trimester of pregnancy [20] It appears that bone mineralizes far more quickly during fetal development than in postnatal life In addition, trabeculae of fetal bone thicken at a speed that is far more rapid than would be compatible with remodeling It thus appears that modeling, not remodeling, is the predominant mechanism responsible for the development of femoral metaphyseal cancellous bone in utero Between and 20 years of age, the trabecular bone volume of iliac bone increases markedly [6] This is entirely due to trabecular thickening, whereas there is no change in trabecular number Trabecular thickening is due to remodeling with a positive balance, which is on the order of 5% of the total amount of bone turned over [18] This means that the amount of bone deposited during a remodeling cycle is slightly higher than the amount of bone removed Since the difference between resorption and formation is very small, a high remodeling activity is necessary to achieve trabecular thickening Bone formation rate and activation frequency are very high in 2e5-year-old children, decrease until approximately age or years, and then increase again to a pubertal peak [18] After the age of puberty, the values decline to the low adult ranges Interestingly, wall thickness increases with age, whereas mineral apposition rate decreases at the same time This indicates that the active osteoblast life span is much shorter in younger children than in adults Regarding the outer bone dimensions and cortical bone, iliac bone development is characterized by an outward modeling drift [18,21] Both cortices move through tissue space in parallel by reciprocal activities of their surfaces [21] The external cortex moves through periosteal apposition and endocortical resorption, whereas the internal cortex migrates laterally through periosteal resorption and endocortical apposition The movement of the external cortex is considerably faster than that of the internal cortex, which leads to an increase in the size of the bone [18,21] At the same time, periosteal apposition is faster than endocortical resorption on the external cortex, whereas endocortical apposition is faster than periosteal resorption on the internal cortex This accounts for the cortical thickening during the growth period This mode of development also implies that a large proportion of iliac trabeculae are created by cancellization of the external cortex rather than by endochondral ossification, as had been previously believed Also, due to trabecular compaction, the internal cortex contains material from what was formerly cancellous bone Cortical bone undergoes intracortical remodeling When intracortical remodeling activity is elevated, cortical porosity is high, because a higher proportion of osteons are “under construction” at any given time point and therefore still have a larger osteonal canal than mature osteons Intracortical remodeling activity decreases after 14 years of age Consequently, cortical porosity decreases after that age [21] Similar to what is observed on the endocortical and periosteal surfaces of the internal and the external iliac cortex, metabolic activity also differs on the intracortical surfaces of the two cortices [21] Intracortical remodeling activity is higher on the osteonal surfaces of the internal cortex than of the external cortex [21] Even within the same osteon, bone formation activity favors the side of the osteonal canal that faces towards the periosteum [22] The general features of iliac bone development are similar between black and white children [23] However, it appears that during pubertal development cortical thickness increases more in black than in white individuals [23] This difference in cortical thickness persists into adulthood and may explain why blacks have fewer fractures than whites [24] The mode of iliac bone development indicates that this process cannot be determined by factors residing in the bone marrow The two endocortical surfaces are in contact with the same bone marrow compartment but undergo different changes Similarly, the cells residing within the same osteonal canal are exposed to the same environment of soluble factors, but bone formation still is predominantly observed on the surface facing the periosteum These observations are more in line with the idea that bone modeling and remodeling are governed by signals from osteocytes that are transmitted to the surfaces via the canalicular network [25] Disorders of Bone Mineralization In the growing skeleton, mineralization occurs in two different types of tissue e growth plate cartilage and bone matrix Deficient mineralization at the level of the growth plate is called rickets, and impaired mineralization of bone matrix is termed osteomalacia By default, only osteomalacia can occur after growth plates have fused Rickets is usually diagnosed clinically or radiographically by evaluating signs and symptoms of the typical growth plate defects Osteomalacia is also associated with clinical, radiological and biochemical abnormalities, but is more precisely evaluated in iliac bone specimens The physiological process of mineralization represents the incorporation of mineral (calcium, phosphorus, PEDIATRIC BONE FIGURE 30.2 Histological stages of heterotopic ossification in FOP Histological analysis of biopsies obtained from FOP patients (obtained prior to diagnosis for FOP) revealed a tissue degradation phase (1AeC) that includes perivascular lymphocyte infiltration (1A), immune cell infiltration (1B), and connective tissue degradation (1C) that is followed by a tissue formation phase that includes fibroproliferation (2A), early cartilage (2B), and endochondral bone formation (2C) stages (Adapted from Glaser et al J Bone Joint Surg 2003;85A:2332-42.) FIGURE 30.5 Histopathology of a POH lesion Initial bone-forming lesions in POH are typically observed as irregular deposits of bone within the dermal tissue are often observed in proximity to subcutaneous adipose tissue Hematoxylin-eosin staining Index A Abuse, see Child abuse Acidebase balance, see Renal tubular acidosis Acute lymphoblastic leukemia (ALL) bone histomorphometry findings, 398 osteoporosis association with treatment, 457e458 ACVR1, fibrodysplasia ossificans progressiva mutations bone morphogenetic protein signaling effects, 830e831 cell function effects, 831 DNA testing, 828e829 R206H mutation, 829e830 variant disease mutations, 829 ADHH, see Autosomal dominant hypocalcemic hypercalciuria ADHR, see Autosomal dominant hypophosphatemic rickets AH, see Autoimmune acquired hypoparathyroidism AHO, see Albright’s hereditary osteodystrophy Albright’s hereditary osteodystrophy (AHO) differential diagnosis, 293 extraskeletal ossification, 833e834 radiographic findings, 293 Alkaline phosphatase, see also Bone-specific alkaline phosphatase; Tissuenon-specific alkaline phosphatase chronic kidney disease bone and mineral disorder evaluation, 804e805 skeletal formation function, 772e773 types and structures, 771e772 X-linked hypophosphatemia activity, 703 ALL, see Acute lymphoblastic leukemia ALPL, see Tissue-non-specific alkaline phosphatase Aluminum, chronic kidney disease bone and mineral disorder evaluation, 805e806 AN, see Anorexia nervosa Androgens fetal levels and functions, 253 peak bone mass effects, 197e198 postnatal bone growth regulation, 72e73 ANKH, craniometaphyseal dysplasia mutations, 549 Anorexia nervosa (AN), osteoporosis association, 469e472 APECED, see Autoimmune polyendocrinopathy candidiasisectodermal dystrophy Aromatase, inhibitor effects on bone turnover markers, 374e375 Asphyxiating thoracic dysplasia (ATD), radiographic findings, 430 ATD, see Asphyxiating thoracic dysplasia Atf4 knockout mouse, 213 osteoblast differentiation role, 47 Atlas technique, bone age assessment, 348e349 Autoimmune acquired hypoparathyroidism (AH), 566 Autoimmune polyendocrinopathy candidiasis-ectodermal dystrophy (APECED), hypoparathyroidism, 561 Autosomal dominant hypocalcemic hypercalciuria (ADHH), 751 Autosomal dominant hypomagnesemia, 753 Autosomal dominant hypophosphatemic rickets (ADHR) features, 708e709 mouse model, 716e717 renal phosphate handling defects, 737 Autosomal recessive hypophosphatemic rickets features, 709 renal phosphate handling defects, 737e738 B BALP, see Bone-specific alkaline phosphatase Bartter syndrome hypoparathyroidism, 566 renal calcium handling defects, 748, 751 BDE, see Brachydactyly type E BFR/BS, see Bone formation rate per bone surface Biglycan, 19 Biopsy, see Histomorphometry, bone Bisphosphonates fibrous dysplasia management, 614 osteogenesis imperfecta management, 524e527 osteoporosis treatment in children, 488e489 Blomstrand dysplasia, features and gene mutations, 541, 570e571 BMD, see Bone mineral density BMPs, see Bone morphogenetic proteins BN, see Bulimia nervosa Bone age, see also Maturation assessment Atlas technique, 348e349 841 BonXpert, 353 comparison of methods, 354 Fels method, 284e285, 353 GreulichePyle method, 284e285, 349 overview, 284e285 Oxford method, 349e350 reliability, 353e354 RocheeWainereThissen technique, 352 TannereWhitehouse method, 284e285, 350e352 radiographic assessment, 284e285 sexual dimorphism in maturation, 344e345, 347 Bone biopsy, see Histomorphometry, bone Bone formation rate per bone surface (BFR/BS), histomorphometry, 389 Bone histomorphometry, see Histomorphometry, bone Bone mineral density (BMD), see also Peak bone mass assessment, see also Dual energy X-ray energy absorptiometry; Quantitative computed tomography; Quantitative ultrasonography children, 311e312 indications, 309e310 overview, 190 radiation dose, 312 radiogrammetry, 312e313 radiographic absorptiometry, 313 classification in children, 311e312 infant early growth and later development, 671 osteoporosis scores in children, 440e441 preterm infants, 661e662, 664, 666e667, 669 structural development, 190e191, 193 Bone morphogenetic proteins (BMPs) fetal bone development role chondrocyte differentiation, 44e45 condensation, 43e44 epithelialemesenchymal interaction, 42 fibrodysplasia ossificans progressiva signaling, 830e831 osteoblast differentiation and activity role in growth plate ossification, 64e65 osteoblast differentiation role, 48 tooth bud development role, 83e84 Bone scan, see Radionuclide scanning Bone sialoprotein (BSP), 24 Bone-specific alkaline phosphatase (BALP), bone formation marker, 364e365 Bone turnover biochemical considerations, 364 lactation, 233e234 markers 842 Bone turnover (Continued) adult clinical practice, 372 aromatase inhibitor effects, 374e375 bone disease finding interpretation and problems, 370e372 chronic disease effects, 374 EhlerseDanlos syndrome type VI effects, 376 formation markers bone-specific alkaline phosphatase, 364e365 osteocalcin, 365 procollagen type I C-terminal propeptide, 365e366 procollagen type I N-terminal propeptide, 365e366 growth prediction, 372e373 normal findings infancy and childhood, 370 perinatal period, 368, 370 postnatal period, 370 puberty, 370 osteogenesis imperfecta, 373e374 pediatric reference data biological variation, 367 clinical considerations, 367e368 growth spurts, 368 reference curve generation, 368e369 sex differences, 368 prospects for study, 376 resorption markers C-terminal cross-linked telopeptide, 362 C-terminal telopeptide of type I collagen, 366 cathepsin K, 367 deoxypyridinoline, 366 Dickkopf-1, 367 N-terminal cross-linked telopeptide, 362 osteoprotegerin, 367 pyridinoline, 366 RANKL, 367 sclerostin, 367 tartrate-resistant acid phosphatase, 366e367 rickets effects, 375e376 table, 362 overview in children, 361e364 pregnancy, 225e226 preterm infants, 664e667, 669 renal osteodystrophy, 799e800 Bone volume per tissue volume (BV/TV), histomorphometry, 387 BonXpert, bone age assessment, 353 Brachydactyly type E (BDE), hyperparathyroidism, 578 Breast milk, see Lactation Bruck syndrome (BS) osteogenesis imperfecta, 517 osteoporosis, 444 BS, see Bruck syndrome BSP, see Bone sialoprotein INDEX Bulimia nervosa (BN), osteoporosis association, 469e472 Burn injury, bone histomorphometry findings, 398 BV/TV, see Bone volume per tissue volume C Cadmium, renal Fanconi’s syndrome induction, 743 Caffey disease, 542 Calbindin-D9K, placental expression, 257 Calciphylaxis, chronic kidney disease bone and mineral disorder, 803e804 Calcitonin (CT) fetal levels and functions, 252 lactation changes, 227 placental expression, 258 pregnancy changes, 227 Calcium bone histomorphometry in deficiency, 393 chronic kidney disease bone and mineral disorder evaluation, 804 deficiency, see Rickets fetus integrated calcium homeostasis blood calcium regulation, 267 placental calcium transfer, 267 skeletal mineralization, 267 metabolism, 247e248 lactation dietary intake, 237e238 metabolism, 232e233 maternal nutrition effects on offspring bone, 671 osteogenesis imperfecta management, 526 parathyroid hormone expression and secretion regulation by calcium, 115e117 homeostasis bone actions, 119e121 kidney actions, 118e119 peak bone mass effects dietary recommendations, 210 geneeenvironment interactions, 209 individual differences of bone response, 208e209 interventional studies, 204e210 observational studies, 204 physical activity interactions, 206e207 pubertal maturation influences on supplementation effects, 205e206 skeletal site responsiveness, 205 placental transport fetal regulation parathyroid hormone, 262e263 parathyroid hormone-related peptide, 260e262 vitamin D, 263 gene expression, 257e258 maternal regulation, 260 measurement, 258e260 overview, 256e257 placental structure, 257 pregnancy dietary intake, 229e230 maternal fluxes from mother to offspring, 223e224 metabolism, 224 preterm infant intake recommendations, 669e670 protein intake effects on bone metabolism, 210e211 renal handling collecting duct, 745 connecting tubule, 744 defects autosomal dominant hypocalcemic hypercalciuria, 751 Bartter syndrome, 748, 751 Dent’s disease, 748 familial benign hypercalcemia, 751e752 familial hypomagnesemia with hypercalciuria and nephrocalcinosis, 751 Gitelman syndrome, 752 Lowe’s syndrome, 748 overview of diseases, 749e750 distal convoluted tubule, 744 loop of Henle, 744 proximal tubule, 743e744 vitamin D and homeostasis 1a,25-dihydroxyvitamin D actions, 170e178 vitamin D metabolites, 178e179 Calcium-sensing receptor (CaSR) hyperparathyroidism defects, 577 hypoparathyroidism defects, 566 knockout mouse and fetal effects, 255e256 placental expression, 258 Campomelia, differential diagnosis, 429 CamuratieEngelmann disease, see Progressive diaphyseal dysplasia Carbonic anhydrase II, osteopetrosis mutations, 544 Cartilage, see also Chondrocyte; Growth plate fibrous dysplasia pathology, 607 histology in skeletal dysplasia diagnosis, 431e433 vascularization, 60e61 Cartilage-hair hypoplasia (CHH) genetics, 434 radiographic findings, 427 Cartilage oligomeric matrix protein, see Thrombospondins CaSR, see Calcium-sensing receptor b-Catenin, see Wnt Cathepsin K bone resorption marker, 367 pycnodysostosis mutation, 547 CCD, see Cleidocranial dysplasia Celiac disease, osteoporosis association, 462e462, 464e466 INDEX Cementum composition, 89e90 types and structural differences, 89 Cerebral palsy (CP), osteoporosis association, 451e454 CF, see Cystic fibrosis Cherubism, dental agenesis, 96 CHH, see Cartilage-hair hypoplasia Child abuse dating of fractures, 305 diaphyseal fracture, 303 differentiation from bone fragility conditions, 490e491, 517e518 imaging modalities, 302 metaphyseal fracture, 303 post-mortem imaging, 303 rib fracture, 304e305 skeletal survey, 302e303 skull fracture, 303 soft tissue injury, 303 subperiosteal new bone formation, 305 Chondrocyte fetal bone development differentiation, 44e45 proliferation and maturation, 45e47 growth plate control of proliferation and differentiation, 57e59 Chondrocyte, phosphate function, 143e144 Chondrodysplasia punctata, differential diagnosis, 429e430 Chronic kidney disease bone and mineral disorder (CKD-MBD) clinical manifestations bone pain, 801 calciphylaxis, 803e804 extraskeletal calcification, 802e803 growth retardation, 802 muscle weakness, 801 skeletal deformities, 801e802 diagnostic evaluation alkaline phosphatase, 804e805 aluminum, 805e806 calcium, 804 magnesium, 804 parathyroid hormone, 805 phosphate, 804 kidney transplantation effects on bone, 811e812 osteoporosis association, 576 pathogenesis, 795e798 radiographic features, 806 renal osteodystrophy bone histomorphometry findings, 398, 806 bone turnover, 799e800 bone volume, 801 mineralization abnormalities, 800e801 treatment calcimimetics, 810 goals, 806e807 growth hormone therapy, 811 mineral nutrition, 807 parathyroidecomy, 810e811 phosphate-binding agents, 807e808 vitamin D therapy, 808e810 Cinacalet, chronic kidney disease bone and mineral disorder management, 810 CKD-MBD, see Chronic kidney disease bone and mineral disorder CLC-5, Dent’s disease defects, 740e741, 748 CLCN7, osteopetrosis mutations, 543e545 Cleft palate, dental agenesis, 96e97 Cleidocranial dysplasia (CCD), hyperdontia, 98 CMD, see Craniometaphyseal dysplasia CoffineLowry syndrome, dietary protein in management, 213 ColeeCarpenter syndrome, 517 Collagen osteogenesis imperfecta mutations, 513e517, 521 type I Caffey disease mutations, 542 fibril assembly, 12, 15e16 genes, 11 processing, 11e14 structure, 11, 14e15 type V genes, 17 processing, 16e17 structure, 16e17 Computed tomography (CT) bone imaging overview, 278e279 quantitative, see Quantitative computed tomography Constitutional delay of puberty, osteoporosis association, 478, 480 CP, see Cerebral palsy Craniometaphyseal dysplasia (CMD), features and gene mutations, 548e549 Craniotubular hyperostoses, features and gene mutations, 552 Crohn’s disease, see Inflammatory bowel disease CRTAP, osteogenesis imperfecta mutations, 290, 516 CT, see Calcitonin; Computed tomography C-terminal cross-linked telopeptide (CTX), 362, 638 C-terminal telopeptide of type I collagen (ICTP), bone resorption marker, 366 CTX, see C-terminal cross-linked telopeptide CYP24A1, see 24-Hydroxylase CYP27B1, see 1a-Hydroxylase CYP2R1, see 25-Hydroxylase Cystic fibrosis (CF), osteoporosis association, 466e469 D DBP, see Vitamin D binding protein Decorin, 19 Deferasirox, renal Fanconi’s syndrome induction, 743 843 Dent’s disease, renal Fanconi’s syndrome, 739e741, 748 Dental development, see Dental occlusion development; Periodontal ligament; Tooth bud; Tooth eruption Dental occlusion development, see also Tooth eruption eruption throughout life, 95 pattern of eruption, 94 speed of eruption, 94 timing of eruption, 93e94 Dentin cell and tissue organization cellular compartment, 88 dentin compartment, 88e89 predentin compartment, 88 circumpulpal dentin, 87e88 composition, 87 defects, 101 extracellular matrix composition, 89 outer peripheral dentin, 86e87 Dentin matrix acidic phosphoprotein-1 (DMP1), 24e25, 70, 709 Dentinogenesis imperfecta (DGI), 101e102, 520 Deoxypyridinoline (DPD), bone resorption marker, 366 Desmosterolosis, 541e542 DGI, see Dentinogenesis imperfecta DGS, see DiGeorge syndrome Diabetes, osteoporosis association, 473e475 Dickkopf-1 (DKK-1), bone resorption marker, 367 DiGeorge syndrome (DGS), hypoparathyroidism, 561 Digital X-ray radiogrammetry (DXR), bone imaging overview, 283 DKK-1, see Dickkopf-1 DLX3, trichodento-osseous dysplasia mutations, 550 DMD, see Duchenne muscular dystrophy DMP1, see Dentin matrix acidic phosphoprotein-1 DNA methylation, see Epigenetics Down syndrome, dental agenesis, 97 DPD, see Deoxypyridinoline Dual energy X-ray energy absorptiometry (DXA), see also Bone mineral density bone edge detection, 317e318 bone size and confounding effect, 318e319 fracture discrimination, 322e323 instrumentation, 316 limitations in infants and children, 315e316 overview, 283, 313e315 osteoporosis diagnosis, 439e440 peak bone mass, 189e190 precision by scan site and subject age, 315 reference data, 319e322 scan acquisition, 316e317 844 INDEX Duchenne muscular dystrophy (DMD), osteoporosis association, 454e455 DXA, see Dual energy X-ray energy absorptiometry DXR, see Digital X-ray radiogrammetry E East syndrome, 753 Eating disorders, osteoporosis association, 469e473 Ectodermal dysplasia, dental agenesis, 96 EDS, see EhlerseDanlos syndrome EhlerseDanlos syndrome (EDS) bone turnover marker effects of type VI disease, 376 osteoporosis, 446e447 Eiken syndrome, hyperparathyroidism, 578 Elastin, Williams syndrome defects, 578 Enamel composition, 86 defects, 100e101 formation, 85e86 structure, 85 Endochondral ossification fetal bone development, 40e41 postnatal bone growth, 55e57 ENS, see Epidermal nevus syndrome Epidermal nevus syndrome (ENS), clinical features, 713 Epigenetics hypophosphatasia, 782 maternal effects on offspring bone, 672e673 vitamin D receptor effects, 170 Eroded surface per bone surface (ES/BS), histomorphometry, 390 ES/BS, see Eroded surface per bone surface Estrogen fetal levels and functions, 253 peak bone mass effects, 197e198 postnatal bone growth regulation, 72e73 Exercise, peak bone mass effects calcium intake interactions, 206e207 fracture prevention in later life, 200e201 geneeenvironment interactions, 202 intense exercise negative effects, 202e203 protein intake interactions, 212e213 public health programs, 201 skeletal site specificity, 201 Extraskeletal calcification chronic kidney disease bone and mineral disorder, 802e803 hereditary forms, see Albright’s hereditary osteodystrophy; Fibrodysplasia ossificans progressiva; Progressive osseous heteroplasia non-hereditary heterotopic ossification, 821e822 prospects for study, 835 F FAM20C, Raine dysplasia mutations, 542 Familial benign hypercalcemia (FHH), 751e752 Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), 751 Fanconi renotubular syndrome (FRTS2), 733e735 FanconieBickel syndrome, 739 FBN1, Marfan syndrome mutations, 447 FD, see Fibrous dysplasia FDH, see Focal dermal hypoplasia Fels method, bone age assessment, 284e285, 353 Fetal bone development, see also Pregnancy adaptive goals, 247 calcium sensing receptor, 255e256 chondrocyte differentiation, 44e45 proliferation and maturation, 45e47 endochondral ossification, 40e41, 264e265 histomorphometry studies, 392 hormone levels and functions androgens, 253 calcitonin, 252 estrogen, 253 fibroblast growth factor-23, 252 parathyroid hormone, 249e250 parathyroid hormone-related peptide, 252e253 vitamin D, 250e252 integrated calcium homeostasis blood calcium regulation, 267 placental calcium transfer, 267 skeletal mineralization, 267 intramembranous ossification, 39e40, 264 kidney function, 264 maternal parathyroid hormone disturbances and fetal response hyperparathyroidism, 265e266 hypoparathyroidism, 266 mineral metabolism calcium, 247e248 magnesium, 248e249 phosphate, 248 twin studies of placental supply versus genetic inheritance, 656e657 molecular regulation condensation, 42e44 epithelialemesenchymal interaction, 41e42 osteoblast differentiation, 47e48 overview, 655e656 parathyroid gland development, 254e255 placental calcium transport fetal regulation parathyroid hormone, 262e263 parathyroid hormone-related peptide, 260e262 vitamin D, 263 gene expression, 257e258 maternal regulation, 260 measurement, 258e260 overview, 256e257 placental structure, 257 placental magnesium transport, 263e264 placental phosphate transport, 263e264 thymus development, 254 timing and sequence, 41 FGFs, see Fibroblast growth factors FHH, see Familial benign hypercalcemia FHHNC, see Familial hypomagnesemia with hypercalciuria and nephrocalcinosis Fibroblast growth factors (FGFs) chondrocyte proliferation and maturation role, 47, 58e59 FGF-23 autosomal dominant hypophosphatemic rickets mutations, 716e717 fetal levels and functions, 252 osteocyte function, 5e6 phosphate homeostasis role, 146, 149e151 receptor interactions, 717 renal phosphate handling regulation, 731e733 rickets findings, 641 secretion regulation by phosphate, 153 osteoblast differentiation and activity role in growth plate ossification, 48, 65 Fibrodysplasia ossificans progressiva (FOP) ACVR1 mutations bone morphogenetic protein signaling effects, 830e831 cell function effects, 831 DNA testing, 828e829 R206H mutation, 829e830 variant disease mutations, 829 bone marrow transplantation, 826, 828 complications, 825 diagnosis and misdiagnosis, 822, 828 epidemiologic factors, 829 histopathology, 826e827 immune system effects, 828 laboratory findings, 826 progressive heterotopic ossification, 822e823 progressive osseous heteroplasia comparison, 835 radiographic features, 825e826 skeletal anomalies, 823, 825 treatment, 832 types and clinical features, 824, 828 Fibromodulin, 19e20 Fibrous dysplasia (FD) bone histomorphometry findings, 397 bone pathology cartilage, 607 deposition and internal structure, 603 lesion growth, 607 mineralization, 603e604 modeling, 602e603 remodeling, 604e606 tumors, 608 vascularity, 606e607 extraskeletal lesions, 592e596 fibro-osseous lesion differential diagnosis, 607 INDEX GNAS mutations, 597e599 hypophosphatemia, 713e714 management bisphosphonates, 614 mutation analysis, 613 overview, 612e613 prospects, 614e615 surgery, 613e614 overview, 589 pathogenesis, 609e612 phenotypic variation determinants allelic expression, 601e602 mutated clone site and time of origin, 600e601 somatic mosaicism, 600 survival and adaptation, 601 radiological findings, 297e298, 591e592 skeletal lesions, 590e591 FKBP10, osteogenesis imperfecta mutations, 290 Focal dermal hypoplasia (FDH), 101 FOP, see Fibrodysplasia ossificans progressiva Formation period (FP), histomorphometry, 390 FP, see Formation period Fracture child abuse differentiation from bone fragility conditions, 490e491, 517e518 metaphyseal fracture, 303 exercise in childhood and prevention in later life, 200e201 osteoporotic fracture, see Osteoporosis preterm infant risks birth to hospital discharge, 666 hospital discharge to two years, 667 two years onwards, 669 FRTS2, see Fanconi renotubular syndrome G GATA3, hypoparathyroidism, deafness, and renal anomalies syndrome defects, 564e565 GCMB, see Glial cells missing B GFD, see Gluten-free diet GH, see Growth hormone Ghosal syndrome, features and gene mutations, 553 Gitelman syndrome, 752 GJA1, oculodental-osseous dysplasia mutations, 550 Gla proteins, see Osteocalcin Glial cells missing B (GCMB), hypoparathyroidism, 562e564 Glucocorticoids Duchenne muscular dystrophy management, 454e455 osteoporosis induction by therapy, 460, 463e464, 483e485 postnatal bone growth regulation, 74 Gluten-free diet (GFD), bone effects in celiac disease, 465e466 GNAS expression regulation, 597 fibrous dysplasia expression, 609 functional consequences of mutation, 599, 609 mutations, 597e599 functions, 834 progressive osseous heteroplasia mutations, 834 pseudohypoparathyroidism mutations, 566e570 stem cell expression, 597 structure, 596 transcript processing, 596 GreulichePyle method, bone age assessment, 284e285, 349 Growth hormone (GH) deficiency and osteoporosis association, 476e478 peak bone mass effects, 198 postnatal bone growth regulation, 71e72 therapy chronic kidney disease bone and mineral disorder, 811 osteogenesis imperfecta, 527e528 X-linked hypophosphatemia, 706 Growth plate chondrocyte proliferation and differentiation, 57e59 vascularization, 60e61 H Heat shock protein-47 (HSP47), collagen type I processing role, 13 Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) clinical physiology, 710 idiopathic hypercalciuria relationship, 710 kidney stones, 710 management and course, 710 mixed skeletal phenotype, 709e710 SLC34A3 mutations, 710e711 sodium/phosphate co-transporter defects, 735 Hertwig’s root sheath, 84 Heterotropic ossification, see Extraskeletal calcification HHRH, see Hereditary hypophosphatemic rickets with hypercalciuria HIF-1a, see Hypoxia-inducible factor-1a Histomorphometry, bone biopsy sample processing, 386 technique, 384e386 disease studies calcium deficiency, 393 fibrous dysplasia, 397 hypophosphatemic rickets, 393e394 idiopathic juvenile osteoporosis, 396e397 osteogenesis imperfecta 845 bisphosphonate treatment findings, 398e399 type I, 394e396 type III, 394e395 type IV, 394e395 type V, 395e396 type VI, 395e396 type VII, 396 osteopetrosis, 397 secondary bone disorders acute lymphoblastic leukemia, 398 burn injury, 398 inflammatory bowel disease, 398 renal osteodystrophy, 398, 806 b-thalassemia, 398 vitamin D deficiency, 393 fetal bone development studies, 392 indications, 399 microscopy, 386 nomenclature, 386e387 parameters dynamic formation parameters, 389e390 reproducibility, 390 static formation parameters, 388e389 static resorption parameters, 390 structural parameters, 387e388 principles, 384e384 reference data for pediatric iliac bone histomorphometry, 390e392 HIV, see Human immunodeficiency virus Homocystinuria, osteoporosis, 448 HRPT2, mutation and hyperparathyroidism-jaw tumor syndrome, 574e575 HSH, see Hypomagnesemia with secondary hypocalcemia HSP47, see Heat shock protein-47 Human immunodeficiency virus (HIV), renal Fanconi’s syndrome induction by treatment, 742e743 1a-Hydroxylase deficiency clinical features, 682e683 laboratory findings, 683 molecular genetics, 683e685 overview, 682 treatment, 687e688 knockout mouse, 174e175 secretion regulation by phosphate, 153 structure and function, 685e687 Toll-like receptor activation, 172 vitamin D metabolism, 164e167, 681e682 24-Hydroxylase knockout mouse, 173e174 vitamin D metabolism, 166e167, 681 25-Hydroxylase knockout mouse, 172 vitamin D metabolism, 163e164, 681 Hyperdontia, 97e98 Hyperparathyroidism brachydactyly type E, 578 calcium-sensing receptor defects, 577 chronic renal failure association, 576 846 Hyperparathyroidism (Continued) Eiken syndrome, 578 familial isolated hyperparathyroidism, 574, 576 gene defects, 560 Jansen’s disease, 577e578 maternal disturbance and fetal response, 265e266 Ollier’s disease, 578 tumors and gene mutations HRPT2 and hyperparathyroidism-jaw tumor syndrome, 574e575 LRP5, 575 MEN1, 573e574 MEN2, 574 PRAD1, 572e573 Rb, 576 RIZ1, 576 Wnt pathway, 575e576 Williams syndrome, 578e579 Hyperphosphatasia differential diagnosis, 294 radiographic findings, 293e294 Hyperprolactinemia, osteoporosis association, 482e483 Hyperthyroidism, osteoporosis association, 475e476 Hypodontia, 98e99 Hypomagnesemia with secondary hypocalcemia (HSH), 752 Hypoparathyroidism, see also Pseudohypoparathyroidism DiGeorge syndrome, 561e562 familial syndromes, 565 gene defects, 559e560 glial cells missing B, 562e564 hypoparathyroidism, deafness, and renal anomalies syndrome, 564e565 maternal disturbances and fetal response, 266 maternal disturbances and fetal response, 266 mitochondrial disorders, 561 pluriglandular autoimmune hypoparathyroidism, 561 X-linked recessive hypoparathyroidism, 559, 561 Hypophosphatasia clinical features adult hypophosphatasia, 776e777 benign prenatal hypophosphatasia, 778 childhood hypophosphatasia, 776 epidemiology, 773 infantile hypophosphatasia, 774e775 odonto hypophosphatasia, 777 perinatal hypophosphatasia, 774 pseudohypophosphatasia, 777 diagnosis alkaline phosphatase activity, 778e779 calcium and phosphate levels, 779 histopathological findings dentition, 780 skeleton, 780 INDEX phosphoethanolamine levels, 779 pyridoxal phosphate levels, 779 pyrophosphate levels, 779 radiographic findings, 293, 779e780 differential diagnosis, 293 epigenetics, 782 history of study, 773 inheritance, 781 mouse model, 785 prenatal diagnosis, 784e785 prognosis, 783 tissue-non-specific alkaline phosphatase deficiency, 780e781 function, 785, 787 gene defects, 781e782 treatment, 783e784 Hypophosphatemia, see also Tumor-induced osteomalcia; X-linked hypophosphatemia autosomal dominant hypophosphatemic rickets features, 708e709 mouse model, 716e717 autosomal recessive hypophosphatemic rickets, 709 bone histomorphometry in hypophosphatemic rickets, 393e394 differential diagnosis, 293 hereditary hypophosphatemic rickets with hypercalciuria clinical physiology, 710 idiopathic hypercalciuria relationship, 710 kidney stones, 710 management and course, 710 mixed skeletal phenotype, 709e710 SLC34A3 mutations, 710e711, 717 phosphate transporter defects, 717e718 prospects for study, 718e719 radiographic findings, 292 Hypothyroidism, osteoporosis association, 476 Hypoxia-inducible factor-1a (HIF-1a), chondrogenesis role, 60 I IBD, see Inflammatory bowel disease ICTP, see C-terminal telopeptide of type I collagen IDH, see Isolated dominant hypomagnesemia Idiopathic juvenile osteoporosis, see Osteoporosis IGFs, see Insulin-like growth factors Ihh, see Indian Hedgehog Immobilization, osteoporosis association, 455e457 Incontinentia pigmenti, dental agenesis, 96 Indian Hedgehog (Ihh), osteoblast differentiation and activity role in growth plate ossification, 64e65 Infants, see Neonatal hypocalcemia; Preterm infants Inflammatory bowel disease (IBD) bone histomorphometry findings, 398 osteoporosis association, 461e464 Insulin-like growth factors (IGFs) chondrocyte proliferation and maturation role, 46e47 IGF-1 peak bone mass effects, 198 postnatal bone growth regulation, 71e72 umbilical venous cord blood levels and bone development, 671e672 Intramembranous ossification fetal bone development, 39e40 postnatal bone growth, 55e57 Ionizing radiation dose and regulations, 285 effective dose by imaging modality, 312 IRH, see Isolated autosomal recessive hypomagnesemia Isolated autosomal recessive hypomagnesemia (IRH), 753 Isolated dominant hypomagnesemia (IDH), 752e753 J Jansen’s disease hyperparathyroidism, 577e578 JDMS, see Juvenile dermatomyositis JIA, see Juvenile idiopathic arthritis Juvenile dermatomyositis (JDMS), osteoporosis association, 458, 461 Juvenile idiopathic arthritis (JIA), osteoporosis association, 459 Juvenile Paget’s disease, features and gene mutations, 550 K KearnseSayre syndrome (KSS), hypoparathyroidism, 561 KenneyeCaffey syndrome, hypoparathyroidism, 565 Kidney transplantation, effects on bone, 811e812 KirkeRichardson syndrome, hypoparathyroidism, 565 Klotho, 717, 736 KSS, see KearnseSayre syndrome L Lactation bone impact in later life, 236e237 bone metabolism, 231e232 bone turnover, 233e234 breast milk bone growth modulators, 237 mineral composition, 237 dietary effects calcium, 237e238 general nutrition, 239 magnesium, 238e239 phosphate, 238e239 vitamin D, 239 zinc, 238e239 847 INDEX hormone levels calcitonin, 234 parathyroid hormone, 234e235 parathyroid hormone-related peptide, 234e235 vitamin D, 234 mineral metabolism calcium, 232e233 magnesium, 233 phosphate, 233 zinc, 233 osteoporosis, 236 skeletal changes, 235e236 LEMD3, osteopoikilosis mutations, 547 LenzeMajewski hyperostotic dysplasia, features and gene mutations, 552e553 LEPRE1, osteogenesis imperfecta mutations, 290 Leptin, umbilical venous cord blood levels and bone development, 671e672 LIM-kinase, Williams syndrome defects, 578 Low-density lipoprotein receptor-related protein-5 (LRP5) autosomal dominant craniotubular hyperostoses mutations, 552 gene polymorphisms and peak bone mass effects, 196e197, 202 osteoporosisepseudoglioma syndrome mutations, 444, 446, 516 parathyroid tumor mutations, 575 Lowe’s syndrome, renal Fanconi’s syndrome, 741, 748 LRP5, see Low-density lipoprotein receptorrelated protein-5 M Macrodontia, 99 Magnesium chronic kidney disease bone and mineral disorder evaluation, 804 fetal metabolism, 248e249 lactation dietary intake, 238e239 metabolism, 233 placental transport, 263e264 pregnancy dietary intake, 230 maternal fluxes from mother to offspring, 223e224 metabolism, 225 renal handling defects autosomal dominant hypocalcemic hypercalciuria, 751 autosomal dominant hypomagnesemia, 753 East syndrome, 753 familial hypomagnesemia with hypercalciuria and nephrocalcinosis, 751 Gitelman syndrome, 752 hypomagnesemia with secondary hypocalcemia, 752 isolated autosomal recessive hypomagnesemia, 753 isolated dominant hypomagnesemia, 752e753 mitochondrial hypomagnesemia, 753 overview of diseases, 749e750 distal convoluted tubule, 747e748 loop of Henle, 746e747 overview, 745 proximal tubule, 746 Magnetic resonance imaging (MRI), bone imaging overview, 282e283 MAPK, see Mitogen-activated protein kinase MAR, see Mineral apposition rate Marfan syndrome (MFS), osteoporosis, 447e448 Matrix, extracellular phosphoglycoprotein (MEP), 26, 70 Maturation, see also Bone age; Puberty indicators, 345e346 initial considerations in assessment, 343e345 sexual dimorphism, 344e345, 347 size in assessment, 347 time concept, 345 variation, 346e347 McCuneeAlbright syndrome, see Fibrous dysplasia Mechanostat model, muscleebone interaction in bone growth and development, 441e443 Megalin, knockout mouse, 172e173 MELAS syndrome, hypoparathyroidism association, 561 Melorheostosis, features and gene mutations, 557e548 MEN1, parathyroid tumor mutations, 573e574 MEN2, parathyroid tumor mutations, 574 Menarche, age at, 357e358 MEP, see Matrix, extracellular phosphoglycoprotein Methotrexate, osteoporosis induction, 457e459, 486 MFS, see Marfan syndrome Microdontia, 98e99 Mineral apposition rate (MAR), histomorphometry, 389 Mineralization, bone, 26e28 Mineralization lag time (Mlt), histomorphometry, 389 Mineralizing surface per bone surface (MS/ BS), histomorphometry, 389 Mineralizing surface per osteoid surface (MS/OS), histomorphometry, 389 Mitogen-activated protein kinase (MAPK), phosphate activation, 151e152 Mlt, see Mineralization lag time MRI, see Magnetic resonance imaging MS/BS, see Mineralizing surface per bone surface MS/OS, see Mineralizing surface per osteoid surface N N-cadherin, condensation role, 42e43 NCAM, see Neural cell adhesion molecule Neonatal hypocalcemia, features, 670 Nephrolithiasis/osteoporosis, hypophosphatemic-2 (NPHLOP2), 735e736 Nephropathic cystinosis, renal Fanconi’s syndrome, 738e739 Neural cell adhesion molecule (NCAM), condensation role, 42e43 NF-kB, see Nuclear factor-kB NHERF1 hypophosphatemia mutations, 718 nephrolithiasis/osteoporosis, hypophosphatemic-2 defects, 735e736 Non-accidental injury, see Child abuse Notch chondrogenesis suppression, 45 osteoblast differentiation suppression, 48 NPHLOP2, see Nephrolithiasis/ osteoporosis, hypophosphatemic-2 NPTm than, see Sodium/phosphate cotransporter N-terminal cross-linked telopeptide (NTX) bone resorption marker, 362 rickets findings, 638 NTX, see N-terminal cross-linked telopeptide Nuclear factor-kB (NF-kB), fetal bone development role, 253 O Ob.S/BS, see Osteoblast surface per bone surface Oc, see Osteocalcin Oc.S/BS, see Osteoclast surface per bone surface Oculodental-osseous dysplasia (ODOD), features and gene mutations, 549e550 ODOD, see Oculodental-osseous dysplasia OI, see Osteogenesis imperfecta Ollier’s disease, hyperparathyroidism, 578 OPG, see Osteoprotegerin OPPG, see Osteoporosisepseudoglioma syndrome OS/BS, see Osteoid surface per bone surface OSCS, see Osteopathia striata with cranial sclerosis Osteitis fibrosa cystica, radiographic features, 806 Osteoblast differentiation, 3e5 fetal bone development and differentiation, 47e48 848 Osteoblast (Continued) growth plate ossification differentiation and activity bone morphogenetic proteins, 64e65 fibroblast growth factors, 65 Indiam Hedgehog, 64e65 Osterix, 63e64 Runx2, 63e64 Wnt, 62e63 morphology, osteogenesis imperfecta function, 521, 523 phosphate function, 143e144 vitamin D receptors, 171 Osteoblast surface per bone surface (Ob.S/BS), histomorphometry, 388e389 Osteocalcin (OC) bone formation marker, 365 function, 23 gene, 23 osteoblast expression, processing, 22e23 structure, 23 Osteoclast abundance, bone modeling and remodeling role, 65e66 bone resorption, 68e69 differentiation, 1e3, 67e68 functional overview, markers, phosphate function, 143 Osteoclast surface per bone surface (Oc.S/BS), histomorphometry, 390 Osteocyte differentiation, functional overview, 5e6 mechanosensing, 70e71 Osteogenesis imperfecta (OI) anesthesia precautions, 520 bone histomorphometry bisphosphonate treatment findings, 398e399 type I, 394e396 type III, 394e395 type IV, 394e395 type V, 395e396 type VI, 395e396 type VII, 396 bone turnover markers, 373e374 breech complications, 520 classification, 289e290, 511e513 clinical features Bruck syndrome, 517 ColeeCarpenter syndrome, 517 osteoporosisepseudoglioma syndrome, 444, 446, 516e517 type I, 514e515 type II, 513e514 type III, 514 type IV, 514 type V, 515e516 type VI, 516 type VII, 516 INDEX diagnosis clinical features cardiovascular involvement, 518 dentinogenesis imperfecta, 520 endocrine changes, 519 neurological involvement, 517e518 ocular changes, 519e520 renal involvement, 518 respiratory problems, 519 connective tissue alterations, 519 differential diagnosis, 517e518 laboratory findings, 517 differential diagnosis, 291e292 idiopathic juvenile osteoporosis comparison, 450 life expectancy, 520e521 management bisphosphonates, 524e527 calcium, 526 growth hormone, 527e528 occupational therapy, 528e529 orthopedic management, 528 prospects, 529e531 vitamin D, 526 pathophysiology bone metabolic activity, 523e524 mineralization defects, 521e522 osteoblast function, 521, 523 prenatal radiology, 288, 290 radiographic findings, 289e292 Osteoid surface per bone surface (OS/BS), histomorphometry, 388e389 Osteomodulin, 19e20 Osteonecrosis, glucocorticoid induction, 485e485 Osteonectin gene, 22 knockout mouse, 22 structure, 22 Osteopathia striata with cranial sclerosis (OSCS), features and gene mutations, 548 Osteopathy of prematurity differential diagnosis, 302 grades, 300, 302 Osteopetrosis bone histomorphometry findings, 397 dental defects, 104 differential diagnosis, 295 radiographic findings, 294e295 types and features autosomal dominant osteopetrosis type II, 544e545 infantile osteopetrosis, 542e543 intermediate osteopetrosis, 543e544 osteoclast-poor osteopetrosis, 545e546 osteopetrosis with renal tubular acidosis, 544 Osteopoikilosis, features and gene mutations, 547 Osteopontin, 25e26 Osteoporosis bone histomorphometry in idiopathic juvenile osteoporosis, 396e397 classification, 444 definition, 439 diagnosis bone mineral density scores, 440e441 differential diagnosis in children, 291e292 dual-energy X-ray absorptiometry, 439e440 overview, 439e440 fragility fracture radiological findings, 298e300 lactation, 236 mechanostat model and muscleebone interaction in bone growth and development, 441e443 pregnancy, 228 prevention and treatment, 486, 487e489 primary disease Bruck syndrome, 444 causes, 445 EhlerseDanlos syndrome, 446e447 homocystinuria, 448 idiopathic juvenile osteoporosis, 448e449 Marfan syndrome, 447e448 osteoporosisepseudoglioma syndrome, 444, 446 prospects for study, 489e490 secondary osteoporosis acute lymphoblastic leukemia treatment, 457e458 anorexia nervosa, 469e472 bulimia nervosa, 469e472 celiac disease, 462, 464e466 cerebral palsy, 451e454 cystic fibrosis, 466e469 diabetes, 473e475 Duchenne muscular dystrophy, 454e455 glucocorticoid therapy induction, 483e485 growth hormone deficiency, 476e478 hyperprolactinemia, 482e483 hyperthyroidism, 475e476 hypothyroidism, 476 immobilization, 455e457 inflammatory bowel disease, 461e464 juvenile dermatomyositis, 458, 461 juvenile idiopathic arthritis, 459 medication induction, 486e487 puberty disorders absence of puberty, 480e481 constitutional delay of puberty, 478, 480 overview of puberty importance in bone development, 478e479 precocious puberty, 480 Turner syndrome, 481e482 systemic lupus erythematosus, 461 Osteoporosisepseudoglioma syndrome (OPPG), features and gene mutations, 444, 446, 516e517 INDEX Osteoprotegerin (OPG) bone resorption marker, 367 fetal bone development, 253 juvenile Paget’s disease mutations, 550 osteoclast formation role, 2, 68 Osterix, osteoblast differentiation and activity role in growth plate ossification, 47, 63e64 Oxford method, bone age assessment, 349e350 P Paget’s disease, see Juvenile Paget’s disease Parathyroid gland chronic kidney disease bone and mineral disorder management with parathyroidecomy, 810e811 development, 254e255 tumors, see Hyperparathyroidism Parathyroid hormone (PTH), see also Hyperparathyroidism; Hypoparathyroidism analogs, 112e113 calcium homeostasis bone actions, 119e121 kidney actions, 118e119 chronic kidney disease bone and mineral disorder evaluation, 805 evolution, 113e114 fetal levels and functions, 249e250 functional overview, 109e111 gene expression regulation, 115 structure, 114, 557 knockout mouse, 265 lactation changes, 226 neonatal mineral homeostasis, 657 phosphate homeostasis, 146e149 secretion regulation by phosphate, 152e153 placental calcium transport regulation, 262e263 pregnancy changes, 226 receptor defects, see specific diseases ligand C-terminal receptors, 129 PTH1R gene, 125 ligand binding and activation mechanisms, 126e128 placental expression, 257 prolonged signaling-inducing ligands, 128e129 topology, 126 signaling, 123e125 structure, 124e126 tissue distribution, 558e559 types and phylogenetic relationships, 125, 558 renal phosphate handling regulation, 730e731 secretion regulation, 115e117 sequences, 111e112 synthesis and processing, 114e115, 557e558 X-linked hypophosphatemia findings, 703 Parathyroid hormone-related peptide (PTHrP) analogs, 112e113 chondrocyte proliferation and maturation role, 45e46, 58 evolution, 113e114 fetal levels and functions, 252e253 functional overview, 109, 121e123 gene, 121e122 knockout mouse, 265 lactation changes, 226e227 parathyroid tumor mutations in pathway, 575e576 placental calcium transport regulation, 260e262 pregnancy changes, 226e227 processing, 122 receptor ligand C-terminal receptors, 129 PTH1R gene, 125 ligand binding and activation mechanisms, 126e128 placental expression, 257 prolonged signaling-inducing ligands, 128e129 topology, 126 signaling, 123e125 structure, 124e126 types and phylogenetic relationships, 125 rickets findings, 637e638 sequence, 122 PBIB, osteogenesis imperfecta mutations, 290 PBM, see Peak bone mass PEA, see Phosphoethanolamine Peak bone mass (PBM) assessment, 190 biomechanical markers during puberty, 194e195 definition, 189 determinants calcium intake dietary recommendations, 210 geneeenvironment interactions, 209 individual differences of bone response, 208e209 interventional studies, 204e210 observational studies, 204 physical activity interactions, 206e207 pubertal maturation influences on supplementation effects, 205e206 skeletal site responsiveness, 205 energy intake and muscle mass development, 202 genetic factors, 195e197 growth hormone/IGF-1 axis, 198 849 mechanical factors age and optimal response to loading, 200 exercise and fracture prevention in later life, 200e201 protein intake bone acquisition effects, 211 bone metabolism effects, 210e211 CoffineLowry syndrome management, 213 dietary recommendations, 213 physical activity interactions, 212e213 pubertal timing, 198e199 sex hormones, 197e198 vitamin D status dietary recommendations, 203e204 interventional studies, 203 observational studies, 203 exercise effects geneeenvironment interactions, 202 intense exercise negative effects, 202e203 public health programs, 201 skeletal site specificity, 201 importance, 189e190 peripubertal transient fragility, 193 structural development, 190e191, 193 timing, 193e194 variability, 194 Peridontium, 95 Periodontal ligament function, 95 maturation, 95 peridontium, 95 PHEX, X-linked hypophosphatemia mouse model studies, 715e716 mutation, 703e704 pathophysiology, 704 Phosphate chondrocyte function, 143e144 chronic kidney disease bone and mineral disorder binding agents for treatment, 807e808 diagnostic evaluation, 804 distribution in body, 141e142 extrarenal soft tissue handling, 142 fetal metabolism, 248 fibroblast growth factor-23 secretion regulation, 153 functions, 141 homeostasis fibroblast growth factor-23, 146, 149e151 overview, 699e700 parathyroid hormone, 146e149 vitamin D, 149 1a-hydroxylase regulation, 153 intestinal absorption, 142 lactation dietary intake, 238e239 metabolism, 233 mitogen-activated protein kinase activation, 151e152 850 Phosphate (Continued) osteoblast function, 143e144 osteoclast function, 143 parathyroid hormone secretion regulation, 152e153 pregnancy dietary intake, 230 maternal fluxes from mother to offspring, 223e224 metabolism, 225 placental transport, 263e264 protein intake effects on bone metabolism, 210e211 renal transport, see Renal phosphate handling Phosphoethanolamine (PEA) hypophosphatasia levels, 779 tissue-non-specific alkaline phosphatase substrate, 785e786 PHP, see Pseudohypoparathyroidism Physical activity, see Exercise PICP, see Procollagen type I C-terminal propeptide PINP, see Procollagen type I N-terminal propeptide POH, see Progressive osseous heteroplasia PPi, see Pyrophosphate PRAD1, parathyroid tumor mutations, 572e573 Precocious puberty, osteoporosis association, 480 Pregnancy, see also Fetal bone development body build, diet, and lifestyle effects on offspring bone, 671 bone impact in later life, 228e229 bone turnover, 225e226 dietary effects on offspring bone calcium, 229e230 general nutrition, 231 magnesium, 230 phosphate, 230 vitamin D, 230e231 zinc, 230 epigenetic effects, 672e673 hormone levels calcitonin, 227 parathyroid hormone, 226 parathyroid hormone-related peptide, 226e227 vitamin D, 226 mineral fluxes from mother to offspring, 223e224 mineral metabolism calcium, 224 magnesium, 225 phosphorous, 225 zinc, 225 osteogenesis imperfecta and breech complications, 520s osteoporosis, 228 placental calcium transport fetal regulation parathyroid hormone, 262e263 INDEX parathyroid hormone-related peptide, 260e262 vitamin D, 263 gene expression, 257e258 maternal regulation, 260 measurement, 258e260 overview, 256e257 placental structure, 257 placental magnesium transport, 263e264 placental phosphate transport, 263e264 skeletal changes, 227e228 vitamin D and calcium nutrition effects on offspring bone, 671 Prenatal bone growth, see Fetal bone growth Prenatal diagnosis hypophosphatasia, 784e785 osteogenesis imperfecta, 288, 290 skeletal dysplasia, 434e435 Preterm infants birth to hospital discharge bone mass, 661e662, 664 bone turnover, 664e666 fracture risk, 666 linear growth, 661 hospital discharge to two years bone mass, 666e667 bone turnover, 667 fracture risk, 667 linear growth, 666 mineral homeostasis at birth preterm infants, 658 term infants, 657e659 nutritional recommendations breast milk versus formula, 670 calcium, 669e670 formula nutrient content, 663e664 vitamin D, 670 osteopathy of prematurity differential diagnosis, 302 grades, 300, 302 rickets of prematurity biochemical findings, 661 clinical features, 661 history of study, 658, 660e661 radiological features, 661 two years onwards bone mass, 668e669 bone turnover, 669 fracture risk, 669 linear growth, 667e668 Procollagen type I C-terminal propeptide (PICP), bone formation marker, 365e366 Procollagen type I N-terminal propeptide (PINP), bone formation marker, 365e366 Progressive diaphyseal dysplasia, features and gene mutations, 549 Progressive osseous heteroplasia (POH) clinical features, 832e833 fibrodysplasia ossificans progressiva comparison, 835 GNAS functions, 834 mutations, 834 heterotopic ossification, 833e834 treatment, 835 Prolactin, hyperprolactinemia and osteoporosis, 482e484 Pseudohypoaldosteronism type I, 758e759 type II, 759 Pseudohypoparathyroidism (PHP) clinical features, 566 differential diagnosis, 293 GNAS mutations, 566e570 radiographic findings, 293 Pseudo-pseudohypoparathyroidism differential diagnosis, 293 radiographic findings, 293 PTH, see Parathyroid hormone PTHrP, see Parathyroid hormone-related peptide Puberty, see also Maturation; Peak bone mass bone turnover markers, 370 menarche, age at, 357e358 osteoporosis in disorders absence of puberty, 480e481 constitutional delay of puberty, 478, 480 overview of puberty importance in bone development, 478e479 precocious puberty, 480 Turner syndrome, 481e482 secondary sexual characteristics breast development stages, 355 clinical evaluation, 355e356, 358 genitalia development stages, 355 self-assessment of status, 356e357 sexual dimorphism in maturation, 344e345, 347 Pycnodysostosis, features and gene mutations, 546e547 PYD, see Pyridinoline Pyle disease, features and gene mutations, 553 Pyridinoline (PYD), bone resorption marker, 366 Pyridoxal phosphate (PLP) tissue-non-specific alkaline phosphatase substrate, 786 hypophosphatasia levels, 779 Pyrophosphate (PPi), hypophosphatasia levels, 779, 786e787 Q qCT, see Quantitative computed tomography Quantitative computed tomography (qCT), see also Bone mineral density fracture discrimination, 329 limitations in children bone length confounding effects, 328e329 overview, 326e327 851 INDEX partial volume effects, 327 reference data, 327e328 scan protocols and multiple outcome measures, 326e327 overview, 283, 323e326 peak bone mass, 190 reference data, 329 Quantitative ultrasonography (QUS) fracture discrimination, 334 limitations, 332e333 overview, 329e332 peak bone mass, 190 reference data, 333e334 QUS, see Quantitative ultrasonography R Radiogrammetry, bone mineral density, 312e313 Radiographic absorptiometry, bone mineral density, 313 Radiography bone age assessment, 284e285 bone imaging overview, 278 ionizing radiation dose and regulations, 285 skeletal survey, see Skeletal survey Radionuclide scanning (RNS), bone imaging overview, 279e281 Raine dysplasia, 542 RANKL bone resorption marker, 367 fetal bone development, 253 knockout mouse, 121 osteoclast formation role, 2e3, 67e68 osteopetrosis mutations, 546 Rb, parathyroid tumor mutations, 576 Remodeling, bone coupling principle, 69e70 overview, 1e2 Renal Fanconi’s syndrome, see Chronic kidney disease bone and mineral disorder Renal osteodystrophy, see Chronic kidney disease bone and mineral disorder Renal phosphate handling overview, 144e145, 727, 729 primary disorders of renal phosphate wasting, 728 regulation dietary phosphate, 730 fibroblast growth factor-23, 731e733 parathyroid hormone, 730e731 vitamin D, 731 rickets due to disorders autosomal dominant hypophosphatemic rickets, 737 autosomal recessive hypophosphatemic rickets, 737e738 Fanconi renotubular syndrome defects, 733e735 hereditary hypophosphatemic rickets with hypercalciuria defects, 735 Klotho defects, 736 nephrolithiasis/osteoporosis, hypophosphatemic-2 defects, 735e736 overview, 733 renal Fanconi’s syndrome acquired, 742e743 Dent’s disease, 739e741 FanconieBickel syndrome, 739 hereditary, 738e742 Lowe’s syndrome, 741 mitochondrial cytopathies, 741e742 nephropathic cystinosis, 738e739 overview, 738 X-linked hypophosphatemic rickets, 736e737 transporters, 145e146, 729e730 Renal tubular acidosis (RTA) acidebase handling in kidney distal tubule, 754e755 proximal tubule, 753e754 distal renal tubular acidosis autosomal dominant disease, 756, 758 autosomal recessive disease, 758 overview, 756 hyperkalemic renal tubular acidosis, 758 mixed type, 758 proximal renal tubular acidosis, 755e756 pseudohypoaldosteronism type I, 758e759 type II, 759 Rickets biochemical changes in nutritional rickets, 636e641 bone histomorphometry hypophosphatemic rickets, 393e394 vitamin D-deficient rickets, 393 bone turnover marker effects, 375e376 calcium deficiency, 632e633 classification, 626e627 clinical presentation, 633e636 definition, 625e626 hereditary abnormalities 1,25-dihydroxyvitamin D resistant rickets clinical and laboratory features, 688 overview, 688 treatment, 693e694 vitamin D receptor defects, 688e693 1a-hydroxylase deficiency clinical features, 682e683 laboratory findings, 683 molecular genetics, 683e685 overview, 682 treatment, 687e688 hereditary disorders, see Hypophosphatemia; X-linked hypophosphatemia history of study, 627 overview, 625 preterm infants biochemical findings, 661 clinical features, 661 history of study, 658, 660e661 radiological features, 661 prevention, 646e647 radiological findings, 296e301, 641e644 renal phosphate handling disorders autosomal dominant hypophosphatemic rickets, 737 autosomal recessive hypophosphatemic rickets, 737e738 Fanconi renotubular syndrome defects, 733e735 hereditary hypophosphatemic rickets with hypercalciuria defects, 735 Klotho defects, 736 nephrolithiasis/osteoporosis, hypophosphatemic-2 defects, 735e736 overview, 733 renal Fanconi’s syndrome acquired, 742e743 Dent’s disease, 739e741 FanconieBickel syndrome, 739 hereditary, 738e742 Lowe’s syndrome, 741 mitochondrial cytopathies, 741e742 nephropathic cystinosis, 738e739 overview, 738 X-linked hypophosphatemic rickets, 736e737 treatment, 644e646 vitamin D deficiency epidemiology, 627e630 induction by low calcium intakes, 631e632 Rieger syndrome, microdontia, 99 RIZ1, parathyroid tumor mutations, 576 RNS, see Radionuclide scanning RocheeWainereThissen technique, bone age assessment, 352 RTA, see Renal tubular acidosis Runx2 endochondral ossification role, 57 osteoblast differentiation and activity role in growth plate ossification, 47, 63e64 S SanjadeSakati syndrome, hypoparathyroidism, 565 Sclerosteosis, features and gene mutations, 551e552 Sclerostin (SOST) bone resorption marker, 367 mutation in disease, 551e552 SERPINH1, osteogenesis imperfecta mutations, 290 Sesame syndrome, 753 SIBLINGS, see Small integrin-binding ligand N-linked glycoproteins Skeletal dysplasia, see also specific diseases classification, 405e424 diagnosis cartilage histology, 431e433 852 INDEX Skeletal dysplasia (Continued) laboratory studies, 431 medical history, 404, 425 molecular analysis, 433e434 physical examination, 425e426 prenatal diagnosis, 434e435 radiology, 426e430 epidemiology, 403 Skeletal survey anatomical localization, 286e287 bone characteristics, 287 characteristic findings, 287 child abuse, 302e303 complications, 287 diagnosis of skeletal dysplasia, 288e289 interpretation, 285e286 sites for radiographs, 285 soft tissue characteristics, 287 SLC34A3, hereditary hypophosphatemic rickets with hypercalciuria mutations, 710e711, 717 SLC4A genes, distal renal tubular acidosis defects, 756 SLE, see Systemic lupus erythematosus SLRPs, see Small, leucine-rich, interstitial proteoglycans Small integrin-binding ligand N-linked glycoproteins (SIBLINGS) bone sialoprotein, 24 dentin matrix acidic phosphoprotein-1, 24e25 functional overview, 23e24 mineralization role, 27e28 osteopontin, 25e26 Small, leucine-rich, interstitial proteoglycans (SLRPs) biglycan, 19 decorin, 19 fibromodulin, 19e20 functional overview, 10, 18e19 osteomodulin, 19e20 Sodium/phosphate co-transporter (NPT) Fanconi renotubular syndrome defects, 733e735 hereditary hypophosphatemic rickets with hypercalciuria defects, 735 renal transport, 145e146, 729e730 SOST, see Sclerostin Structural hierarchy, bone, 9e10 Systemic lupus erythematosus (SLE), osteoporosis association, 461 T TannereWhitehouse method, bone age assessment, 284e285, 350e352 Tartrate-resistant acid phosphatase (TRAP), bone resorption marker, 366e367 Taurodontism, 99e100 TBCE, see Tubulin-specific chaperone TBX, DiGeorge syndrome mutations, 562 TBXAS1, Ghosal syndrome mutations, 553 TCIRG1, osteopetrosis mutations, 543 TDO, see Trichodento-osseous dysplasia Testosterone, see Androgens TFIIB, vitamin D receptor interactions, 168 TGF-b, see Transforming growth factor-b b-Thalassemia, bone histomorphometry findings, 398 Thrombospondins cartilage oligomeric matrix protein, 20e21 knockout mice, 21e22 ligands, 21 structure, 21 types, 20 Thymus, development, 254 Thyroid hormone osteoporosis role hyperthyroidism, 475e476 hypothyroidism, 476 postnatal bone growth regulation, 73e74 TIO, see Tumor-induced osteomalcia Tissue-non-specific alkaline phosphatase (TNAP) defects, see Hypophosphatasia structure and function, 27, 771e773, 785, 787 substrates, 785e786 TNAP, see Tissue-non-specific alkaline phosphatase TNX, EhlerseDanlos syndrome defects, 446 Tooth bud cementum composition, 89e90 types and structural differences, 89 dental agenesis, 95e97 dentin cell and tissue organization cellular compartment, 88 dentin compartment, 88e89 predentin compartment, 88 circumpulpal dentin, 87e88 composition, 87 extracellular matrix composition, 89 outer peripheral dentin, 86e87 enamel composition, 86 formation, 85e86 structure, 85 root formation/eruption, 84e85 steps in tooth formation initial phase, 83 morphogenesis, 83e84 terminal differentiation, 84 Tooth eruption, see also Dental occlusion development defects, 92 dental follicle role, 90e91 genetic control, 91 mechanisms intraoral eruption, 91e92 intraosseous eruption, 91 overview, 90 prefunctional stage, 84 speed, 91 Trabecular number, histomorphometry, 387e388 Trabecular thickness, histomorphometry, 387e388 Transforming growth factor-b (TGF-b), latency-associated peptide mutations in progressive diaphyseal dysplasia, 549 TRAP, see Tartrate-resistant acid phosphatase Trichodento-osseous dysplasia (TDO), features and gene mutations, 101, 550 Tubulin-specific chaperone (TBCE), mutation in disease, 565 Tumor-induced osteomalcia (TIO) course, 712 evaluation, 711e712 overview, 711 pathology, 711 pathophysiology, 712e713 related syndromes, 713e714 treatment, 712 Turner syndrome dental defects, 99 osteoporosis association, 481e482 U Ulcerative colitis, see Inflammatory bowel disease Ultrasonography (US) bone imaging overview, 281e282 quantitative, see Quantitative ultrasonography US, see Ultrasonography V Van Buchem disease, features and gene mutations, 552 Vascular endothelial growth factor (VEGF) endochondral ossification role, 57 vascularization of cartilage and bone, 60e61 VDR, see Vitamin D receptor VEGF, see Vascular endothelial growth factor Vitamin D bone histomorphometry in deficiency, 393 calcium homeostasis 1a, 25-dihydroxyvitamin D actions, 170e178 vitamin D metabolites, 178e179 chronic kidney disease bone and mineral disorder management, 808e810 deficiency, see Rickets fetal levels and functions, 250e252 lactation changes, 226 status effects, 239 maternal nutrition effects on offspring bone, 671 metabolism 1a-hydroxylase, 164e167, 681e682 24-hydroxylase, 166e167, 681 25-hydroxylase, 163e164, 680e681 853 INDEX knockout mouse studies, 172e178 overview, 163 rickets, 639e640 X-linked hypophosphatemia, 702e703 osteogenesis imperfecta management, 526 osteoporosis prevention, 488 parathyroid hormone expression regulation, 115 peak bone mass effects dietary recommendations, 203e204 interventional studies, 203 observational studies, 203 phosphate homeostasis, 149 placental calcium transport regulation, 263 pregnancy changes, 226 status effects, 230e231 preterm infant intake recommendations, 670 renal phosphate handling regulation, 731 umbilical venous cord blood markers insulin-like growth factor-1, 671e672 leptin, 671e672 Vitamin D binding protein (DBP), knockout mouse, 172 Vitamin D receptor (VDR) co-activators, 168 co-repressors, 168e169 domains, 167 epigenetic effects, 170 gene, 690 knockout mouse, 175e178 non-classical effects, 170 post-translational modifications, 167e168 response elements and target genes, 169e170 rickets defects clinical and laboratory features, 688 DNA-binding domain defects, 690e692 ligand-binding domain defects, 692e693 miscellaneous mutations, 693 overview, 688 treatment, 693e694 structure, 688e690 tissue distribution, 171 W Wall thickness, histomorphometry, 389 Williams syndrome, hyperparathyroidism, 578e579 Wnt chondrogenesis suppression, 45 osteoblast differentiation role, 48 osteoblast ossification differentiation and activity role, 62e63 WTX, osteopathia striata with cranial sclerosis mutations, 548 X X-linked hypophosphatemia (XLH) biochemical findings alkaline phosphatase activity, 703 hypophosphatemia evaluation, 702 parathyroid hormone, 703 vitamin D metabolism, 702e703 bone histomorphometry in hypophosphatemic rickets, 393 dental defects, 103e104, 701e702 growth, 701 heredity, 704 long-term sequelae, 703 mouse models bone and teeth phenotypes, 714 overview, 714 PHEX function, 715e716 phosphate wasting, 714 vitamin D metabolism, 714e715 PHEX mutation, 703e704 pathophysiology, 704 renal phosphate handling defects in rickets, 736e737 skeletal findings, 700e701 sporadic cases, 704 treatment adjunctive therapy, 706 complications, 707 dosing of calcitriol and phosphorous, 705e706 early childhood, 705 goals, 705 monitoring, 705 surgery, 706e707 XLH, see X-linked hypophosphatemia Z Zinc lactation dietary intake, 238e239 metabolism, 233 pregnancy dietary intake, 230 maternal fluxes from mother to offspring, 223e224 metabolism, 225 ... 1 .2 OS/BS (%) 34 Æ 29 Ỉ 13 22 Ỉ 26 Ỉ 17 Æ OV/BV (%) 4.0 Æ 1 .2 2.6 Æ 1.0 2. 1 Ỉ 1.0 2. 2 Ỉ 0.9 1.6 Ỉ 0.7 Ob.S/BS (%) 8.5 Ỉ 4.1 8 .2 Ỉ 4.4 6.7 Ỉ 4.5 7.9 Ỉ 4.1 5.3 Ỉ 2. 7 Ob.S/OS (%) 26 Ỉ 14 29 Ỉ 15 29 ... 17.0e 22. 9 C.Wi (mm) 5.3 Ỉ 1.4 7.9 Ỉ 1.7 7.1 Ỉ 1.8 8.6 Ỉ 2. 4 8 .2 Ỉ 1.6 Ct.Wi (mm) 0.70 Ỉ 0 .28 0.97 Ỉ 0.37 0.90 Ỉ 0.33 1.18 Ỉ 0.35 1.01 Ỉ 0 .20 BV/TV (%) 17.7 Ỉ 2. 6 22 .4 Ỉ 4 .2 24.4 Ỉ 4.3 25 .7 Ỉ 5.3 27 .8... DTDST SLC26A2 sulfate transporter Diastrophic dysplasia (DTD) AR 22 2600 5q 32- 33 DTDST SLC26A2 sulfate transporter MED, autosomal recessive type (rMED; EDM4) AR 22 6900 5q 32- 33 DTDST SLC26A2 sulfate