The m.4308G>A variant was detected with 1% heteroplasmy in the unaffected mother of a child with a homozygous mutation in a novel candidate gene (MAN1A2), and the 89% heteroplasmic m.14484T>C known Leber’s hereditary optic neuropathy variant was present in the unaffected father of a child with a homozygous variant in a novel candidate gene (KNDC1). Here, KNDC1 is linked to hereditary optic neuropathy.