In particular, mutations in the ND1 subunit of CI [MIM #252010] are associated with Leigh syndrome [MIM #256000]; cardiomyopathy; epilepsy; encephalopathy; mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) [MIM #54000]; Leber hereditary optic neuropathy (LHON) [MIM #535000] and an overlap syndrome comprising clinical features of both LHON and MELAS [1–7]. The gene discussed is MT-ND1; the disease is MELAS.