Unlike LHON, which results from mutations in mitochondrial DNA (mtDNA)-encoded complex I subunits, ADOA disease results primarily from mutations in two nuclear genes, OPA1 at 3q28 and OPA4 at 18q12, and displays incomplete penetrance and variable expressivity in families [2-7]. The gene discussed is OPA1; the disease is Leber hereditary optic neuropathy.