CHAPTER 50 ■ ODOR: UNUSUAL ALISON ST GERMAINE BRENT INTRODUCTION The human nose can discriminate approximately 4,000 odors! Occasionally, parents bring an infant or a child to the emergency department (ED) complaining of an unusual smell Adolescents are more likely to note a new or an unusual odor themselves and present to the ED with specific complaints Before the development of sophisticated laboratory tests, clinicians relied heavily on the sense of smell and often made clinically perceptive diagnoses by aroma alone Today, by incorporating the sense of smell into a clinical skill set, an astute provider can make a presumptive diagnosis of a metabolic disorder, intoxication, or infection, and institute lifesaving therapy prior to laboratory confirmation The incidence of an unusual odor is dependent on the underlying cause For example, in diabetic ketoacidosis (DKA), with an incidence of 80 to 150 per 1,000 person-years, the distinctive aroma of acetones is identified in approximately 30% of children at the time of initial diagnosis of diabetes mellitus By contrast, patients with inborn errors of metabolism (IEM) have an incidence of in 1,400 births with only a very small percentage being associated with abnormal odors (see Chapter 95 Metabolic Emergencies ) PATHOPHYSIOLOGY The olfactory area extends from the roof of the nasal cavity approximately 10 mm down the septum and superior turbinates bilaterally The exact mechanism of stimulation of the olfactory receptors is unknown Smell is more acute in the darkness and is believed to be linked to blood cortisol levels The unique odor emitted by a person is produced by a combination of body secretions and excretions, particularly those from the oropharynx, nasopharynx, and the respiratory tract, plus aromas from the skin and cutaneous lesions, urine, feces, and flatus The most significant components of odor in healthy humans are the apocrine glands These secretions are initially odorless, but bacterial breakdown that results in fatty acid production can cause an offensive odor Body odor is altered by hygiene, metabolism, toxins, infections, and systemic disease When a child is unable to detect odor, anosmia should be considered When a child complains of strange odors, especially if no one else can identify them, temporal lobe epilepsy should be contemplated DIFFERENTIAL DIAGNOSIS Several conditions, including metabolic disorders, intoxications, infections, dermatologic conditions, foreign bodies, various abnormalities of the body orifices, and a variety of systemic diseases, may result in noxious odor ( Table 50.1 ) Metabolic Disorders The most common metabolic disorder with a characteristic odor is DKA ( Table 50.2 ) The characteristic breath odor is described as sweet, fruity, or similar to nail polish remover This distinctive aroma is caused by acetone from the breakdown of ketone bodies to ketoacids (acetone, acetoacetate, and βhydroxybutyrate) It is important to note that any condition that results in a marked metabolic acidosis with ketosis will result in the characteristic sweet or fruity breath IEM that result in altered body, breath, or skin odors are rare individually, but as a composite, they reflect a significant percentage of life-threatening illnesses of infancy and account for 42% deaths within the first year of life (see Chapter 95 Metabolic Emergencies ) Although definitive diagnosis depends on specific identification of serum and urine amino and organic acid levels, many such conditions are associated with a positive urine ferric chloride test, which when performed in the ED can yield a presumptive diagnosis ( Table 50.2 ) It is important to make a specific diagnosis, even in a dying child, to help parents understand what happened and to provide genetic counseling that may impact reproductive planning Phenylketonuria is a disorder of amino acid metabolism associated with a deficiency of phenylalanine dehydroxylase and dihydropteridine reductase, which forces use of minor metabolic pathways of phenylalanine, resulting in the buildup of phenylacetic acid It is the buildup of phenylacetic acid in sweat and urine that causes the characteristic aroma described as musty, mousy, horsey, wolflike, barny, or stale sweaty locker-room towels Clinical features of untreated phenylketonuria include white-blond hair, blue eyes, fair complexion, eczema, microcephaly, hypertonicity, seizures, and progressive mental deterioration Although neonatal screening detects most of these cases, the observation of a characteristic odor in an infant should prompt immediate appropriate laboratory studies, which may include a urine ferric chloride test in the ED Prompt diagnosis and dietary restriction of phenylalanine promote normal development Maple syrup urine disease is caused by a metabolic defect in the decarboxylation of the ketoacids of the branched-chain amino acids (leucine, isoleucine, and valine), which results in their accumulation in the blood Sotolon (4; 5-dimethyl-3-hydroxy-2[5H] Furanone), a metabolite of isoleucine in the urine, produces the characteristic odor described as maple syrup, caramellike, malty, or boiled Chinese herbal medicine Children with this disorder can have variable clinical manifestations, ranging from decreased appetite, vomiting, and ataxia, to progressive acidosis, seizures, coma, and death Prompt diagnosis and limitation of dietary branched-chain amino acids promote normal development Oasthouse urine disease, or methionine malabsorption syndrome, is caused by defective transport by the intestines and kidneys of methionine and, to a lesser extent, leucine, isoleucine, valine, tyrosine, and phenylalanine The unabsorbed methionine in the gut is broken down by colonic bacteria to α-hydroxybutyric acid, which causes the distinctive odor, described as dried malt or hops (as in breweries), dried celery, or yeast Clinical presentation includes fair hair and skin, hyperpnea, extensor spasms, fever, edema, and mental retardation Successful treatment consists of a methionine-restricted diet TABLE 50.1 CLINICAL SOURCE AND CAUSE OF UNUSUAL ODORS ... the characteristic odor described as maple syrup, caramellike, malty, or boiled Chinese herbal medicine Children with this disorder can have variable clinical manifestations, ranging from decreased