Phenotypic variability in male patients carrying the mutant ornithine transcarbamylase (OTC) allele, Arg40His, ranging from a child with an unfavourable prognosis to an asymptomatic older adult

Abstract

In five different Japanese families, we identified six male hemizygotes (aged 6, 9, 15, 17, 56, and 65 years) and a putative candidate (aged 48 years), carrying a mutant allele of the ornithine transcarbamylase (OTC) gene, a G to A substitution at nucleotide 119 in exon 2 generating histidine in place of arginine. OTC activity in the necropsied liver tissue was reduced to ~12% of the control and that of COS 1 cells transfected with Arg40His OTC cDNA was 10.2 ± 1.8% of the control transfected with wild type OTC cDNA. Clinical features ranged from death during a hyperammonaemic attack (1 9 year old) to a 65 year old asymptomatic man. We consider that the amount of protein ingested by these subjects may be one predisposing factor leading to the manifestation of this disease.