OBJECTIVETo investigate the clinical and genetic features of two families with late-onset glutaric aciduria type II caused by ETFDH mutations.

METHODSTarget gene sequence capture and next generation sequencing were used for sequencing of suspected patients and their family members. The patients' clinical features were retrospectively analyzed and literature review was performed.

RESULTSThe probands of the two families had a clinical onset at the ages of 10 years and 5.5 years respectively, with the clinical manifestations of muscle weakness and muscle pain. Laboratory examinations revealed significant increases in the serum levels of creatine kinase, creatine kinase-MB, and lactate dehydrogenase. Tandem mass spectrometry showed increases in various types of acylcarnitines. The analysis of urine organic acids showed an increase in glutaric acid. Electromyography showed myogenic damage in both patients. Gene detection showed two novel mutations in the ETFDH gene (c.1331T>C from the mother and c.824C>T from the father) in patient 1, and the patient's younger brother carried the c.1331T>C mutation but had a normal phenotype. In patient 2, there was a novel mutation (c.177insT from the father) and a known mutation (c.1474T>C from the mother) in the ETFDH gene. Several family members carried such mutations. Both patients were diagnosed with glutaric aciduria type II. Their symptoms were improved after high-dose vitamin B2 treatment.

CONCLUSIONSFor patients with unexplained muscle weakness and pain, serum creatine kinase, acylcarnitines, and urinary organic acids should be measured, and the possibility of glutaric aciduria type II should be considered. Genetic detection is helpful to make a confirmed diagnosis.