Leber hereditary optic neuropathy (LHON) is a maternally inherited mitochondrial disorder that primarily affects the optic nerve. We report a case of reduced visual acuity secondary to optic atrophy in a 13-year-old boy. Transient seizures developed subsequently. Serial magnetic resonance imaging of the brain showed posterior reversible encephalopathy syndrome. Ragged red fibers were not detected on skeletal muscle biopsy. A 11778G>A mitochondrial DNA point mutation was identified in the lymphocytes isolated from peripheral blood. His younger brother was a carrier with the same mutation. The presentation of this case is unusual documenting LHON in association with PRES.