Molybdenum-cofactor deficiency: an easily missed cause of neonatal convulsions.

Intractable seizures in the neonatal period may be caused by molybdenum-cofactor deficiency, an inborn error which combines the deficiencies of sulphite oxidase and xanthine dehydrogenase. The neurological symptoms of molybdenum cofactor and isolated sulphite oxidase deficiencies are identical. Two new cases are reported, and the literature on neonatal convulsions due to molybdenum-cofactor and sulphite deficiencies is reviewed. Because of the high incidence of neonatal convulsions a search for this deficiency is advocated in each case of unexplained refractory neonatal convulsions. Diagnosis may be missed or delayed on standard metabolic screening for several reasons discussed. By simply using a sulphite strip test in a fresh urine sample an indication for the defect can be obtained. Antenatal diagnosis can be performed by assay of sulphite oxidase activity in a chorionic villus sample.