Related Self Assessment Question Blood samples of a 3-day-old full-term infant are sent for screening to identify diseases that would have serious, permanent consequences without prompt and appropriate treatment. What is the most appropriate treatment for hypothyroidism? A. Special infant formula B. Hormone therapy C. Vitamin therapy D. Antibiotic prophylaxis E. Sunlight EXPLANATION: In galactosemia, an enzyme deficiency (galactose-l-phosphate uridyl transferase) results in a block in the metabolic pathway of galactose and leads to the accumulation of galactose-l-phosphate in the tissues. Infants with this condition develop serious damage to liver, brain, and eyes after being fed milk containing lactose (a disaccharide compound of glucose and galactose). Clinical manifestations include lethargy, vomiting and diarrhea, hypotonia, hepatomegaly and jaundice, failure to thrive, and cataracts. The course of the disease in untreated patients is variable; death from liver failure and inanition can occur; most untreated patients develop physical and mental retardation. Treatment consists of prompt elimination of lactose-containing milk from the diet in infancy and, as a more varied diet is introduced, exclusion of foods that contain casein, dry milk solids, whey, or curds. Phenylketonuria, a genetically determined disorder with an autosomal recessive pattern of inheritance, is caused by the absence of an enzyme that metabolizes phenylalanine to tyrosine. The resultant accumulation of phenylalanine and its metabolites in the blood leads to severe mental retardation in untreated patients. Treatment consists of a diet that maintains phenylalanine at levels low enough to prevent brain damage but adequate to support normal physical and mental development. Careful supervision of the low-phenylalanine diet and monitoring of blood levels are necessary. Special formulas are available for the infant; older children have difficulty following the diet. It is not clear when and if the diet can be discontinued. Biotinidase is the enzyme responsible for breakdown of biocytin (the lysyl precursor of biotin) to free biotin. Deficiency of the enzyme, which is inherited as an autosomal recessive trait, results in malfunctioning of the biotin-dependent mitochondrial enzymes and in organic acidemia. Clinical problems related to the deficiency appear several months or years after birth and include dermatitis, alopecia, ataxia, hypotonia, seizures, developmental delay, deafness, immunodeficiency, and metabolic acidosis. The treatment is lifelong administration of free biotin. The treatment of congenital hypothyroidism with oral levothyroxine sodium should begin as early as possible to prevent psychomotor retardation. Periodic measurement of T3, T4, and TSH is necessary to assess the response to therapy and the need for adjustment of the dose of thyroxine. Careful evaluation of somatic growth by plotting sequential measurements and monitoring bone age is essential. The answer is B.
