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extended hyperalimentation, intestinal resection, or chronic diarrhea Affected infants usually present with failure to thrive and developmental delay Older patients more commonly exhibit weight loss, constipation, and weakness The diagnosis of vitamin B12 or folic acid deficiency may be suggested by the finding of anemia with megaloblastic features Megaloblastic anemia is characterized by normochromic, macrocytic red blood cells, hypersegmented neutrophils, and an elevated serum level of lactic dehydrogenase The diagnosis is confirmed by the finding of low serum levels of folic acid or vitamin B12 and the response to folic acid or vitamin B12 replacement therapy TABLE 62.1 PALLOR WITHOUT ANEMIA Physiologic (“fair-skinned”) Shock: septic, hypovolemic, neurogenic, cardiogenic, anaphylactoid Hypoglycemia and other metabolic derangements Respiratory distress Skin edema Pheochromocytoma Hypoplastic and Aplastic Anemias Pallor is usually the first sign of aplastic or hypoplastic anemia These anemias may be congenital or acquired Congenital aplastic anemias are most commonly part of larger syndromes The two major recognized syndromes are Diamond– Blackfan and Fanconi anemia Diamond–Blackfan syndrome is a congenital hypoplastic anemia commonly detected in the first few months of life The anemia can be severe at the time of diagnosis The red cells are normocytic or macrocytic The reticulocyte count is characteristically low Associated congenital anomalies include microcephaly, cleft palate, web neck, and thumb irregularities The diagnosis is made by examination of a bone marrow aspirate evidencing markedly reduced or absent erythrocyte precursors with normal marrow cellularity TABLE 62.2 PALLOR WITH ANEMIA I Decreased erythrocyte or hemoglobin production A Nutritional deficiencies Iron deficiency Folic acid and vitamin B12 deficiency or associated metabolic abnormalities B Aplastic or hypoplastic anemias Diamond–Blackfan anemia Fanconi anemia Aplastic anemia a Transient erythroblastopenia of childhood Malignancy: leukemia, lymphoma, neuroblastoma a C Abnormal heme and hemoglobin synthesis Anemia of chronic disease Lead poisoning a Sideroblastic anemias Thalassemias II Increased erythrocyte destruction A Erythrocyte membrane defects: hereditary spherocytosis, elliptocytosis, stomatocytosis, pyknocytosis, paroxysmal nocturnal hemoglobinuria B Erythrocyte enzyme defects Defects of hexose monophosphate shunt: G6PD deficiency most common Defects of Embden–Meyerhof pathway: pyruvate kinase deficiency most common C Hemoglobinopathies Sickle cell syndromes a Unstable hemoglobins D Immune hemolytic anemia Autoimmune hemolytic anemia a Isoimmune hemolytic anemia a Infection a Viral: mononucleosis, influenzas, coxsackievirus, measles, varicella, cytomegalovirus b Bacterial: Escherichia coli, Pneumococcus, Streptococcus, typhoid fever, Mycoplasma Drugs: antibiotics Inflammatory and collagen vascular disease Malignancy a E Microangiopathic anemia Disseminated intravascular coagulation a Hemolytic uremic syndrome a Cavernous hemangioma III Blood loss A Severe trauma a B Anatomic lesions Meckel diverticulum Peptic ulcer Idiopathic pulmonary hemosiderosis a a Conditions that are known to present with acute, life-threatening anemia or are associated with other serious abnormalities G6PD, glucose-6-phosphate dehydrogenase TABLE 62.3 RELATIVELY COMMON CAUSES OF PALLOR OR ANEMIA Decreased erythrocyte or hemoglobin production Iron deficiency Transient erythroblastopenia of childhood Increased erythrocyte destruction Sickle cell syndromes Autoimmune hemolytic anemia G6PD deficiency Blood loss G6PD, glucose-6-phosphate dehydrogenase Fanconi anemia is an autosomal recessive condition that results in progressive bone marrow failure generally after or years of age Fanconi anemia is characterized by a normochromic or macrocytic anemia as well as concurrent reductions in both white cell and platelet counts, in contradistinction to Diamond–
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