CLINICAL HISTORY.—This 2-year-old girl was admitted to Children's Hospital of Los Angeles because of slow physical and mental development. The admission diagnosis was phenylketonuria, based on an elevated serum phenylalanine level done at another hospital when she was 13 months of age.
She had been treated by a low phenylalanine diet, but this was poorly tolerated. She became lethargic, her hair became dry, she was irritable, and had poor muscle tone. At 6 months of age, she was able to sit with support, but not until 13 months was she able to sit unsupported. She stood with support at age 13 months. She spoke no words. The mother's pregnancy was uncomplicated and the family history noncontributory.
On physical examination, the child was small and had prominent epicanthic folds, depressed nasal bridge, large mouth with thick, full lips, and low-set, somewhat pointed ears. She was blond and had blue eyes.