A genetically heterogeneous rare autosomal recessive metabolic disorder characterized by onset in infancy of poor feeding, intractable SEIZURES, and severe psychomotor retardation. Characteristic biochemical abnormalities include decreased serum URIC ACID and increased urine sulfite levels due to the combined enzymatic deficiency of XANTHINE DEHYDROGENASE and SULFITE OXIDASE, both of which use molybdenum as a cofactor. Most affected individuals die in early childhood. OMIM: 252150
