A family with riboflavin-reactive lipid deposition myopathy caused by a novel compound heterozygous mutation in the electron transfer flavoprotein dehydrogenase gene.

We report a family with riboflavin-reactive multiple acyl-CoA dehydrogenase deficiency (RR-MADD) partially caused by a novel mutation in the electron transfer flavoprotein dehydrogenase gene (ETFDH). The RR-MADD family was identified by physical examination, electromyography, and muscle biopsy of the proband. Laboratory examination and electromyography suggested a muscle disease of the lipid storage myopathies. This was confirmed by a muscle biopsy that revealed lipid deposition in the muscle fibers. The proband's sister previously had a similar disease, so the family underwent genetic testing. This revealed complex heterozygous ETFDH mutations c.389A > T (p. D130V) and c.1123C > A (p. P375T) in the proband and her sister, of which c.1123C > A (p. P375T) is a novel pathogenic mutation. The proband was treated with riboflavin and changes in physical symptoms and laboratory tests were evaluated before and after treatment. The discovery of a novel locus further expands the ETFDH mutation spectrum and suggests that genotyping is vital for early detection of RR-MADD as it can greatly improve the prognosis.