Partial ornithine transcarbamylase deficiency in females: diagnosis by an immunohistochemical method.

Females heterozygous for the X-linked urea cycle disorder, ornithine transcarbamylase (OTC) deficiency have a significant risk of developing hyperammonaemia. Diagnosis of this genetic defect in a proband is the essential starting point for family studies. By an immunohistochemical analysis of the liver specimens fixed in 10% formalin, we confirmed heterozygous status for OTC deficiency in two female patients, a 15-year-old girl and a 2-year-old girl, who died of hyperammonaemia. Since most affected males lack cross reactive materials (CRM), an immunochemical analysis should be useful for the diagnosis of most heterozygous females.