Response to Therapy in Carnitine/Acylcarnitine Translocase (CACT) Deficiency Due to a Novel Missense Mutation

Deficiency of carnitine/acylcarnitine translocase (CACT) is an autosomal recessive disorder of the carnitine cycle resulting in the inability to transfer fatty acids across the inner mitochondrial membrane. Only a limited number of affected patients have been reported and the effect of therapy on this condition is still not well defined. Here, we report a new patient with this disorder and follow the response to therapy. Our patient was the product of a consanguineous marriage. He presented shortly after birth with cardiac myopathy and arrhythmia coupled with severe non-ketotic hypoglycemia. Initial metabolic studies indicated severe non-ketotic C6-C10 dicarboxylic aciduria, plasma carnitine deficiency, and a characteristic elevation of plasma C:16:0, C18:1, and C18:2 acylcarnitine species. Enzyme assay confirmed deficiency of CACT activity. Molecular studies indicated that this child was homozygous, and both parents heterozygous, for a single bp change converting glutamine 238 to arginine (Q238R). Therapy with a formula providing most of the fat via medium chain triglycerides (MCT) and carnitine supplementation reduced the concentration of long-chain acylcarnitines and reversed cardiac symptoms and the hypoglycemia. These results suggest that carnitine and MCT may be effective in treating this defect of long-chain fatty acid oxidation.