Prospective treatment in carnitine–acylcarnitine translocase deficiency

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Carnitine-acylcarnitine translocase (CACT) deficiency is a rare disorder that results in long-chain fatty acids being unavailable for mitochondrial beta-oxidation and ketogenesis. It can present in the neonatal period or infancy with a severe clinical form, typically with convulsions, hypothermia, encephalopathy, cardiomyopathy and liver dysfunction, or with a milder phenotype with episodes of hypoglycaemia and hyperammonaemia during intercurrent illness. Investigations show hypoketonaemia, intermittent dicarboxyluria and hypocarnitinaemia with grossly elevated acylcarnitines. Enzyme assay or DNA analysis confirms the diagnosis. The severe phenotype results in severe disability or death. The less severe phenotype can also cause significant disability secondary to hypoglycaemia and/or hyperammonaemia at presentation. We report the outcome of two siblings with CACT deficiency. The index patient presented at the age of 2 months during a respiratory illness with hypoglycaemia, hyperammonaemia and cardiorespiratory collapse. Acylcarnitine profiles showed decreased free carnitine but striking elevations of long-chain acylcarnitines. Urine organic acids showed dicarboxylic aciduria. Fatty acid oxidation studies showed reduced oleate and myristate oxidation. His acylcarnitine profile normalized after he was started on a medium-chain triglyceride (MCT) low-fat diet and carnitine supplementation. Low CACT activity on enzyme assay confirmed the diagnosis. He has resulting profound developmental delay and epilepsy. The sibling was prospectively treated with a low-fat MCT diet and carnitine supplementation. Acylcarnitine profile at birth also showed elevated long-chain acylcarnitines. Fatty acid oxidation studies confirmed the diagnosis. To date he has normal development and has not had any significant periods of hypoglycaemia or hyperammonaemia.