Linkage of a molybdenum cofactor deficiency (MoCoD) gene to an 8-cM region on chromosome 6p21.3 has been localized by homozygosity mapping in 2 consanguineous affected kindreds of Israeli-Arab origin, including 5 patients, at the Department of Genetics, Tamkin Research Facility, Technion-Israel Institute of Technology, Haifa, Israel. These findings allow prenatal diagnosis with microsatellite markers and carrier detection of this fatal disorder. 
COMMENT. Molybdenum cofactor deficiency (MoCoD) is a fatal inherited, autosomal recessive, disorder manifesting with neonatal seizures unresponsive to therapy, opisthotonus, retardation, craniofacial dysmorphic features, ectopia lentis, and progressive neurologic deterioration. MoCoD is caused by abnormal biosynthesis of the Mo-complexed pterin cofactor for the enzymes: sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. Postnatal diagnosis is suggested by hypouricemia and elevated urinary sulfite, and confirmed by sulfite oxidase deficiency in fibroblasts. Microsatellite markers may now be used for prenatal diagnosis, in addition to chorionic villus sampling and sulfite oxidase assay. Dietary therapy with methionine restriction and cysteine supplements has provided short-term clinical improvements (see Progress in Pediatric Neurology II, PNB Publ, 1994;p475).