A mother and her son are reported who suffer from Leber's hereditary optic neuropathy (LHON) with the 11778 mtDNA mutation. In both subjects additional clinical and paraclinical evidence of a cerebral demyelinating disease was found. This combination has been reported incidentally in females, rarely in males. Magnetic resonance imaging and proton spectroscopy findings are reported. These findings are compatible with multiple sclerosis.