MT-TL1 and MELAS: Because of the large diversity of mutations in this patient group, we only had the power to test the role of the most common m.3243A>G MTTL1 mutation (Table 1), which is typically associated with the MELAS (Mitochondrial Encephalopathy with Lactic Acidosis and Stroke-like episodes) or MIDD (maternally inherited deafness and diabetes) syndromes, but may also result in peripheral neuropathy [10].