No evidence of association between optic neuritis and secondary LHON mtDNA mutations in patients with multiple sclerosis

Leber's Hereditary Optic Neuropathy (LHON) shares features with Multiple Sclerosis (MS). Both diseases develop optic lesions. Frequent secondary LHON mutations in MS patients may explain the optic damage. Here, we tested the hypothesis that secondary LHON mutations are associated with optic neuritis (ON) in MS patients. We recruited 56 MS subjects with ON and 47 MS subjects without ON. DNA was extracted by salting out, after sampling of peripheral blood from each participant. We completed Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) analysis with appropriate primers and restriction endonucleases for seven secondary LHON mutations. Products were visualized using 3% agarose gel electrophoresis with the aid of DNA safe stain in a UV transilluminator. Accuracy of the genotyping procedure was confirmed by sequencing. Data was analyzed using chi square and Fisher exact tests and logistic regression analysis. There was no significant difference between the numbers of MS subjects with ON and without ON that carried secondary LHON mutations (T4216C [P=0.1], A4917G [P=0.2], G13708A [P=0.6], G15257A [P=1], G15812A [P=0.8], G15927A [P=1], G15928A [P=0.4]). The evidence from the present study are not consistent with the hypothesis that secondary LHON mutations are associated with ON in MS subjects.