Nonfamilial and unusual cases of Leber's hereditary optic neuropathy identified by mitochondrial DNA analysis.

Peripheral blood mitochondrial DNA (mtDNA) samples from 11 patients with acute optic neuritis or insidious optic atrophy were examined for the mutation at nt 11778 and nt 3460 in polymerase chain reaction products. The mtDNA mutation at nt 11778 was evident in 8 cases, which led to a definite diagnosis of Leber's hereditary optic neuropathy (LHON); 4 of the cases were familial and the remaining 4 cases were nonfamilial. None of the 11 patients showed the nt 3460 mutation. The symptoms and signs were variable among the LHON cases with nt 11778 mutation. Assessment of mtDNA provides a useful diagnostic aid for clinically undefined, seemingly nonfamilial or atypical cases of Leber's hereditary optic neuropathy, particularly in bilateral, insidious optic nerve disease in early childhood.