Homozygous NADH-methemoglobin reductase and aspartylglucosaminidase deficiencies in a moderately retarded Sicilian child.

We report on a 10-year-old boy with generalized deficiency of both NADH-methemoglobin reductase and aspartylglucosaminidase. Although the two enzymatic defects, both autosomal recessive traits, are associated with severe mental retardation, the patient was less retarded than his sister who had only aspartylglucosaminuria.