Review of the Literature Isolated Sulfite Oxidase Deficiency: A Case Report With a Novel Mutation and

ABSTRACT. Isolated sulfite oxidase deficiency is arare but devastating neurologic disease that usually pre-sents in early infancy with seizures and alterations inmuscle tone. Only 21 cases have been reported in theliterature. We report a case of a newborn infant boy withisolated sulfite oxidase deficiency who presented withgeneralized seizures on his fourth day of life. Plasmatotal homocysteine was not detectable. Urinary sulfite,thiosulfate, and S -sulfocysteine levels were elevated. Thepatient began a low-methionine and low-cysteine dietand was treated with thiamine and dextromethorphan.However, he became increasingly microcephalic and wasseverely developmentally delayed. Mutation analysis ofthe sulfite oxidase gene revealed that the patient washomozygous for a novel 4-base pair deletion, and both ofhis parents were found to be heterozygous carriers of thesame deletion. We reviewed the clinical, biochemical,neuroradiologic,andneuropathologicfeaturesinallpub-lished cases of isolated sulfite oxidase deficiency. Sei-zures or abnormal movements were prominent featuresin all cases. Developmental delays were reported in 17cases. Ectopia lentis was detected in 9 cases. Clinicalimprovement with dietary therapy was seen in only 2patients, both of whom presented after the age of 6months and had relatively mild developmental delays.Plasma or urinary