A novel two-nucleotide deletion in the ornithine transcarbamylase gene causing fatal hyperammonia in early pregnancy

Abstract

Ornithine transcarbamylase (OTC) deficiency shows X-linked inheritance. Typically, symptomatic females (who constitute 15%-20% of all carriers) have markedly reduced enzyme activity and show first symptoms in late infancy or early childhood. Here we present the case of a previously asymptomatic 24-year-old woman who died of severe hyperammonemia associated with orotic aciduria but normal OTC activity in the fourth month of pregnancy. DNA analysis revealed a novel mutation in form of the deletion of two nucleotides (T892, G893) in exon 9 of the OTC gene, leading to a frame shift and an aberrant gene product. We suggest that OTC deficiency should be suspected in any patient who presents with hyperammonia in the presence of otherwise normal liver function. (Hepatology 1996 Dec;24(6):1413-5)