COQ4 and Menkes disease: Eleven patients (17%) were found to carry disease-causing mutations in six MD-related genes, i.e. COQ4, COQ7, NDUFA9, OPA1, SURF1, and TAZ. Twelve patients (18%) had mutations in 10 non-MD-associated genes, i.e. ATP1A3, ALDH5A1, ARX, FA2H, KCNT1, LDHD, NEFL, NKX2-2, TBCK, and WAC. From all the genes identified (MD and non-MD), five showed autosomal dominant inheritance, nine showed autosomal recessive inheritance, and two showed X-linked inheritance.