Ekbom's syndrome of photomyoclonus, cerebellar ataxia and cervical lipoma is associated with the tRNALys A8344G mutation in mitochondrial DNA

We have investigated nine maternal offsprings to patients with a hereditary syndrome of cerebellar ataxia, photomyoclonus, skeletal deformities and lipoma, originally described by Ekbom. The nine family members underwent a thorough neurological examination, neurophysiological investigations and molecular genetic analysis of mtDNA from lymphocytes and muscle. Clinical examination showed a partial syndrome in one relative and minor signs and symptoms in three additional offsprings. We found the heteroplasmic tRNA^LyS A8344G point mutation in mtDNA in all investigated maternal offsprings. The fraction of mutated mtDNA ranged from 33 to 87% in lymphocytes and from 59 to 92% in muscle tissue. Analysis of mtDNA from a lipoma showed a high level (96%) of the tRNA^LyS A8344G mutation. We conclude that Ekbom's syndrome is a mitochondrial encephalomyopathy associated with the same heteroplasmic tRNA mutation as seen in myoclonus epilepsy with ragged-red fiber (MERRF) syndrome.