Difficulty differentiating Leber's from dominant optic neuropathy in a patient with remote visual loss

A 31-year-old man who inexplicably lost vision as a child was referred for evaluation of bilateral optic atrophy. Other family members had also suffered unexplained visual loss. He had asymmetric impairment of visual acuity, central scotomas, and optic disc pallor. He also had a tritan color vision defect and excavation of the temporal portion of his optic discs, two features that were consistent with autosomal dominant optic atrophy. However, examination of the mitochondrial DNA of the proband and of two of his relatives revealed a mutation at nucleotide 11778, known to be associated with Leber's hereditary optic neuropathy. This case illustrates the difficulty physicians may encounter when trying to clinically differentiate Leber's from dominant optic atrophy in patients with remote visual loss, and it emphasizes the importance of obtaining a molecular assay for a mitochondrial mutation in cases of ambiguously classified hereditary optic neuropathy.