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Very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD; OMIM#201475) is a rare metabolic disorder of mitochondrial fatty acid oxidation. VLCADD includes three clinical forms that are grouped based on disease severity. Here, we present two unrelated patients suspected of having VLCADD based on a newborn screening test. One patient was diagnosed in the neonatal period and, to date, has not shown any symptoms or signs associated with VLCADD; in contrast, diagnosis was delayed in the other patient after events of hypoketotic hypoglycemia and steatohepatitis. Repeated biochemical analyses and a liver biopsy implied VLCADD, and direct sequencing analysis led to the discovery of three novel mutations, including an identical missense variant (p.Ser207Pro) on ACADVL. Our patients were the first cases of the milder form of VLCADD, and the identical mutation detected might represent a founder mutation in the Korean population and be associated with the milder phenotype of VLCADD., (© 2016 by the Association of Clinical Scientists, Inc.)

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is characterized by impaired mitochondrial β-oxidation of fatty acids. The fatty acid oxidation plays a significant role in energy production especially in skeletal muscle. VLCAD is one of four acyl-CoA dehydrogenases with different-chain length specificity and catalyzes the initial step in mitochondrial β-oxidation of fatty acids. While the clinical phenotypes in neonates and infants are described as severe, adolescent-onset or adult-onset VLCAD deficiency has a more benign course with only skeletal muscle involvement. These myopathic phenotypes are characterized by episodic muscle weakness and rhabdomyolysis triggered by fasting and strenuous exercise. We report a male teenager who manifested repeated episodes of rhabdomyolysis immediately after exertional exercise. Rhabdomyolysis was diagnosed based on the marked elevation of serum creatine kinase and myoglobinuria. Acylcarnitine analysis by tandem mass spectrometry (MS/MS) revealed elevation of serum tetradecenoylcarnitine (C14:1-AC), which represents an abnormal acylcarnitine profile associated with the mitochondrial β-oxidation defect. High performance liquid chromatographic analysis showed decreased production of 2-hexadecenoyl-CoA (C16:1) from palmitoyl-CoA (C16:0), indicating the defect of VLCAD activity. Direct sequencing of the acyl-CoA dehydrogenase, very long-chain gene (ACADVL) that codes VLCAD revealed a heterozygous mutation (c.1242G>C) in exon 12 (E414D), which is a novel mutation in myopathic-type VLCAD deficiency. Because VLCAD functions as a homodimer, we assume that this heterozygous mutation may exhibit dominant-negative effect. This patient remains asymptomatic thereafter by avoiding exertional exercise. The findings of reduction of enzyme activity and clinical features associated with this novel missense mutation of VLCAD are discussed.