Cerebral dysfunction in asymptomatic carriers of ornithine transcarbamylase deficiency.

We tested the hypothesis that female carriers of ornithine transcarbamylase (OTC) deficiency have cerebral dysfunction as a consequence of episodic hyperammonemia. Seven such carriers were identified by pedigree analysis and protein-tolerance testing. The Wechsler Adult Intelligence Scale was used for evaluation. All IG scores were above 100, but in the protein-tolerant siblings, the full-scale and performance IQ scores were higher by 5.6 and 9.9 points, respectively (P less than 0.02). The absolute difference between the verbal and performance IQ scores was greater in the OTC carriers by 7.8 points (P less than 0.01). This study suggests that clinically asymptomatic carriers of OTC deficiency may have intellectual deficits, perhaps as a result of episodic hyperammonemia.