A patient with carnitine-acylcarnitine translocase deficiency with a mild phenotype.

Carnitine-acylcarnitine translocase deficiency, a rare beta-oxidation defect, is manifest in most cases by cardiomyopathy and death in early childhood. We report an affected patient, 3 years of age, who has had no serious complications. The residual enzyme activity in fibroblasts was higher than in previously reported patients, which may explain the benign clinical course.

Neonatal hyperammonemia caused by a defect of carnitine-acylcarnitine translocase.

Carnitine-acylcarnitine translocase deficiency is a newly recognized inborn error of metabolism that involves transport of long-chain fatty acids into mitochondria, which in turn impairs mitochondrial beta-oxidation, and ketogenesis. We report a new familial example; the affected twins had neonatal distress, hyperammonemia, and transient intracardiac conduction defects. Clinical and biochemical analysis of both our patients and the two previously reported patients revealed that this inherited defect could be manifested during the neonatal period without any of the signs classically associated with fatty oxidation defects. In contrast, all four patients had sustained and "isolated" hyperammonemia, which could be misinterpreted as being caused by urea cycle defects. We conclude that carnitine-acylcarnitine translocase deficiency is a potential differential diagnosis in neonates with unexplained neonatal hyperammonemia. Cardiac and muscle involvement may represent further early pivotal symptoms.