Dietary treatment of tyrosinemia type I: importance of methionine restriction.

A patient with tyrosinemia type I was treated with formula 3200 AB. This dietary approach lowered the elevated plasma phenylalanine and tyrosine levels but failed to eliminate the hypermethioninemia and the concomitant clinical abnormalities of ascites and other abnormal liver functions. Strict control of dietary intake of methionine, as well as phenylalanine and tyrosine, by a synthetic amino acid mixture or by a combination with formula 3200 AB maintained all plasma amino acids within the normal limits, permitted normal physical growth, and eliminated all hepatic and renal abnormalities. We suggest that restriction of only phenylalanine and tyrosine is inadequate in treating tyrosinemia type I during the acute phase. In such cases, the dietitian should use 3200 AB formula with caution until the acute phase of the disease subsides and plasma methionine levels return to normal.