Report on a new patient with combined deficiencies of sulphite oxidase and xanthine dehydrogenase due to molybdenum cofactor deficiency.

A newborn infant exhibiting seizures and spastic tetraparesis at the age of 1 week was shown to excrete excessive quantities of sulphite, taurine, S-sulphocysteine and thiosulphate, characteristic of sulphite oxidase deficiency. In addition, increased renal excretion of xanthine and hypoxanthine combined with a low serum and urinary uric acid was consistent with xanthine dehydrogenase deficiency. Both deficiencies could be established at the enzyme level. The primary defect giving rise to the combined abnormalities is the absence of a molybdenum cofactor, a molybdenum-containing pterin being an essential component of both enzymes. The patient developed a severe neurological syndrome, brain atrophy and lens dislocation and died at the age of 22 months. Attempts at treatment, such as oral administration of ammonium molybdate, sodium sulphate, D-penicillamine, 2-mercaptoethane sulphonic acid, pyridoxine and thiamine did not influence the clinical course.