mtDNA haplogroup J: a contributing factor of optic neuritis

Optic neuritis frequently occurs in multiple sclerosis (MS), and shares sev eral similarities with the optic neuritis of Leber's hereditary optic neuro pathy (LHON), which is mainly due to maternally transmitted mitochondrial D NA (mtDNA) mutations, Our report shows for the first time that a mitochondr ial DNA background could influence the clinical expression of MS, One Europ ean mtDNA haplogroup was found only in MS patients with optic neuritis but not in MS patients without visual symptoms. Therefore, we hypothesize that mtDNA haplogroup J might constitute a risk factor for optic neuritis occurr ence when it is coincidentally associated with MS, but not be a risk factor for developing MS per se as suggested previously.