Distribution of HLA-Dw2 in optic neuritis and multiple sclerosis indicates heterogeneity

Introduction - The human leukocyte antigen (HLA) phenotype Dw2 is known to be increased in multiple sclerosis (MS), but only slightly in optic neuritis (ON). Materials and methods - 127 consecutive patients with unilateral monosymptomatic ON were typed genomically for HLA-DR and -DQ genes. Results - The frequency of HLA-Dw2 among ON patients (47%) was found to be significantly higher than among 250 controls (30%) but significantly lower than in a group of 245 MS patients (60%), all of the same ethnic origin. At the group level, these figures can be calculated to indicate that 53% of the ON patients belong to the group of ''MS-type ON'' (95% confidence limits 25-78%). A compilation of published data on the frequency of the HLA-DR17(3),DQ2 haplotype, prompted by a slight increase in this material, revealed a significant association with this haplotype in ON, after compensation for the increase of Dw2. Conclusion - ON differs from both MS and controls regarding HLA-Dw2. Thus, a substantial number of patients with ON may suffer from conditions not immune-genetically related to MS, which might be designated as non-MS type ON. This condition may be more common in men and in young patients of both sexes.