Primary ornithine transcarbamylase deficiency. A case report and electron microscopic study.

Histological and ultrastructural findings obtained upon examination of a liver biopsy specimen from a 2-year-old girl with primary ornithine transcarbamylase (OTC) deficiency are presented. The OTC activity in the hepatic tissue of the patient was 7% that of the normal level. Light microscopic observation showed diffusely swollen hepatocytes with pale or empty cytoplasm due to accumulation of glycogen. Neither fat degeneration nor necrosis was evident. Electron microscopy revealed strikingly abnormal hepatocyte mitochondria, which showed marked polymorphism with elongation and enlargement, ring- or dumbbell-shaped configurations, and irregular distribution and shortening of the cristae. Mitochondria showing degenerative alterations such as swelling and rarefaction, which have been reported in cases of Reye's syndrome, were present, but their number was very small. Other organelles showed no remarkable change. It is suggested that the mitochondrial changes seen in OTC deficiency are essentially different from those in Reye's syndrome, which otherwise is clinically and biochemically very similar to OTC deficiency.