Very long chain acyl-CoA dehydrogenase deficiency(VLCADD)is a disorder involving the initial step of fatty acid beta-oxidation in the mitochondrial matrix. VLCADD can present at various ages,from the neonatal period to adulthood,with symptoms including hypoglycemia,rhabdomyolysis,skeletal muscle weakness and cardiomyopathy,and poses the greatest risk of complications during intercurrent illness or after prolonged fasting. Early diagnosis,treatment,and surveillance can reduce mortality. The most common diagnostic evaluation methods are plasma acylcarnitine profiles and ACADVL gene molecular testing. Functional testing,including white blood cell or fibroblast enzyme assay,is a useful diagnostic adjunct if molecular sequencing alone is insufficient to deter-mine the diagnosis or uncharacterized mutations are identified. Treatment emphasizes the avoidance of fasting and often includes a specialized diet that is high carbohydrate/low longchain fat which is supplemented by medium chain triglycerides(MCT).very-long chain acyl coenzyme A dehydrogenase