The most widespread mtDNA pathogenic variant in Leigh syndrome is at mtDNA, 8993T>G/C, affecting the ATP6 subunit of the ATPase, and is also associated with maternally inherited Leigh syndrome (MILS), as well as neuropathy, ataxia, and retinitis pigmentosa (NARP) [23,24]. The gene discussed is MT-ATP6; the disease is maternally-inherited Leigh syndrome.