Use of immunocytochemical analysis of a duodenal biopsy specimen to identify a carrier of ornithine transcarbamylase deficiency

DEFICIENCY of ornithine transcarbamylase (OTC, or ornithine carbamoyltransferase [EC 2.1.3.3]), a urea-cycle enzyme located in the mitochondrial matrix, is one of the most frequently inherited causes of ammonia intoxication, with inheritance following an X-linked dominant pattern. Recently, prenatal diagnosis of OTC deficiency has been achieved with use of DNA restriction-fragment–length polymorphisms (RFLPs) at the OTC locus.1 , 2 However, correct identification of women who are carriers of OTC deficiency is essential for accurate prenatal diagnosis because RFLP analysis does not identify a specific mutation at the OTC locus. Carriers of OTC deficiency have been identified by measuring urinary excretion of orotic acid . . .