MT-ND3 and Leber hereditary optic neuropathy: This study reports a rare case of adult-onset Leigh syndrome (LS) and Leber hereditary optic neuropathy and dystonia (LDYT) overlap syndrome caused by the m.10197G>A mutation in ND3. A review of the literature was conducted to investigate the clinical spectrum, treatment and outcome resulting from the m.10197G>A mutation.