Diagnostic assessment and long-term follow-up of 13 patients with Very Long-Chain Acyl-Coenzyme A dehydrogenase (VLCAD) deficiency.

Very Long-Chain Acyl-CoA dehydrogenase (VLCAD) deficiency is an inborn error of mitochondrial long-chain fatty acid oxidation (FAO) most often occurring in childhood with cardiac or liver involvement, but rhabdomyolysis attacks have also been reported in adults. We report in this study the clinical, biochemical and molecular studies in 13 adult patients from 10 different families with VLCAD deficiency. The enzyme defect was demonstrated in cultured skin fibroblasts or lymphocytes. All patients exhibited exercise intolerance and recurrent rhabdomyolysis episodes, which were generally triggered by strenuous exercise, fasting, cold or fever (mean age at onset: 10 years). Inaugural life-threatening general manifestations also occurred before the age of 3 years in four patients. Increased levels of long-chain acylcarnitines with tetradecenoylcarnitine (C14:1) as the most prominent species were observed in all patients. Muscle biopsies showed a mild lipidosis in four patients. For all patients but two, molecular analysis showed homozygous (4 patients) or compound heterozygous genotype (7 patients). For the two remaining patients, only one mutation in a heterozygous state was detected. This study confirms that VLCAD deficiency, although being less frequent than CPT II deficiency, should be systematically considered in the differential diagnosis of exercise-induced rhabdomyolysis. Measurement of fasting blood acylcarnitines by tandem mass spectrometry allows accurate biochemical diagnosis and should therefore be performed in all patients presenting with unexplained muscle exercise intolerance or rhabdomyolysis.