Is the mitochondrial DNA involved in determining susceptibility to multiple sclerosis?

An increasing number of case reports on Leber's hereditary optic neuropathy (LHON) associated mitochondrial (mt)DNA point mutations in patients with multiple sclerosis (MS) raised the possibility that mitochondrial determinants may contribute to genetic susceptibility to MS. These observations prompted many laboratories including ours to perform comprehensive sequencing or large scale screening of the mtDNA in MS patients. Here we review the available data arguing for or against a mitochondrial hypothesis for MS. We conclude that pathogenic mtDNA point mutations are not associated with typical forms of this disease. A very small subgroup of MS patients, usually with prominent optic neuritis (PON), may carry pathogenic LHON mutations. This partial overlap between the two diseases may be related to the association of MS with a mtDNA haplotype (a set of mtDNA polymorphisms) within which pathogenic LHON mutations preferentially occur.