Hypoketotic hypoglycemia, hepatomegaly, cardiomyopathy and myopathy, rhabdomyolysis, elevated creatinine kinase, lipid infiltration of liver and muscle, and defective activity of very long-chain acylCoA dehydrogenase (VLCAD) are the major phenotypic expression. VLCAD is bound to the inner mitochondrial membrane. It was first delineated in 1992 as catalyzing the dehydrogenation of acylCoA esters of 14 to 20 carbon length in the first step of mitochondrial fatty acid oxidation. Impairment of very long-chain acyl-CoA dehydrogenation can result in severe organ dysfunction, especially of the heart, liver, and skeletal muscle. The disease may present in the first days of life. Organic acid analysis of the urine may reveal dicarboxylic aciduria. Unfortunately, during interepisode periods of health, when many diagnostic work ups occur, organic acid analysis is normal.