ISOLATED SULFITE OXIDASE DEFICIENCY

Isolated sulfite oxidase (SO) deficiency is an autosomal recessively i nherited inborn error of sulfur meta bolism. In this report of a ninth patient the clinical history, laboratory results, neuropathological f indings and a mutation in the sulfite oxidase gene are described. The data from this patient and previously published patients with isolated sulfite oxidase deficiency and molybdenum cofactor deficiency are sum marized to characterize this rare disorder. The patient presented neon atally with intractable seizures and did not progress developmentally beyond the neonatal stage. Dislocated lenses were apparent at 2 months . There was increased urine excretion of sulfite and S-sulfocysteine a nd a decreased concentration of plasma cystine. A lactic acidemia was present for 6 months. Liver sulfite oxidase activity was not detectabl e but xanthine dehydrogenase activity was normal. The boy died of resp iratory failure at 32 months. Neuropathological findings of cortical n ecrosis and extensive cavitating leukoencephalopathy were reminiscent of those seen in severe perinatal asphyxia suggesting an etiology of e nergy deficiency. A point mutation that resulted in a truncated protei n missing the molybdenum-binding site has been identified.