AHOMOCYSTEINEMIA IN MOLYBDENUM COFACTOR DEFICIENCY

We report an infant with molybdenum cofactor deficiency (MCD) and a un ique clinical presentation of hemiplegia, hypotonia, dystonia, and bil ateral basal ganglia changes. Biochemistry revealed absent serum homoc ysteine, low concentrations of plasma cystine, high levels of urinary S-sulfocysteine and sulfite, and high levels of oxypurines in serum an d urine. The depletion of cysteine and cystine through reaction with s ulfite suggests that other thiols and thiol-dependent proteins may be similarly depleted. Ahomocysteinemia may be a clue to the mechanism of cytotoxicity in MCD.