Prenatal diagnosis of congenital methemoglobinemia with mental retardation.

A case of congenital enzymopenic methemoglobinemia associated with severe mental retardation is described. The deficiency of cytochrome b5 reductase activity in the erythrocytes and the leukocytes of the propositus is demonstrated by kinetic measurement and by disc gel electrophoresis. Analysis of cultured amniotic fluid cells during a second pregnancy of the mother revealed an almost complete deficiency of the enzyme. The absence of cytochrome b5 reductase activity in the blood from the aborted fetus confirmed the prenatal diagnosis. The data presented support the opinion that in pregnancies at risk for the severe form of congenital enzymopenic methemoglobinemia, prenatal diagnosis is warranted.