Hypermethioninemia in an infant.

We discuss an infant with hepatitis and hypermethioninemia. An inborn error of metabolism, such as methionine adenosyltransferase deficiency or hereditary tyrosinemia, was originally thought to be the basis for these abnormalities. The infant's subsequent clinical course, however, was incompatible with such a diagnosis; the hypermethioninemia was instead due to the trilogy of prematurity, hepatitis, and a high-protein, high-methionine diet.