Phenylalanine-tyrosine deficiency syndrome as a complication of the management of hereditary tyrosinemia.

A male infant with type I hereditary tyrosinemia developed a phenylalanine-tyrosine deficiency syndrome after receiving a synthetic diet which was low in these amino acids. The syndrome was characterized by growth failure, anorexia, lethargy, and hypotonia. Hypophenylalaninemia and hypotyrosinemia were discovered. The blood concentration of most other amino acids were increased. Supplementation of the patient's diet with phenylalanine and tyrosine resulted in a prompt and dramatic reversal of both clinical and biochemical abnormalities. Dietary therapy had no effect on the child's hepatic cirrhosis.