The affected maternal uncle (V-26) exhibited polymorphisms defining mtDNA haplogroup U6a1a1 (www.phylotree.org), including the variant, m.4172 T > A (MT-ND1)/p.L289Q, that affects an amino acid position already implicated in several other LHON cases, m.4171C > A/p.L289M [20–26]. The gene discussed is MT-ND1; the disease is Leber hereditary optic neuropathy.