HLA associations with multiple sclerosis in the Canary Islands

The study of small island populations has proved informative with respect to the epidemiology and genetics of many complex traits including multiple sclerosis. The class II major histocompatibility antigen DR15 is associated with multiple sclerosis in all groups except Sardinians, where the primary association is with DR4. We compared HLA-DR and -DQ allele frequencies in a representative sample of patients with multiple sclerosis from the Canary Islands with appropriate controls. There was a significant association with DR15 (patients 21/53: 40%: controls 11/55; 20%: chi2=4.09; pc=0.04; relative risk [RR]=1.98). DRB1*1501-DRB5*0101 was present in 17/53 (32%) patients in whom sub-types could be identified compared with 6/55 (11%) controls (chi2=7.21; pc=< 0.01; RR=2.94). All DR15 positive controls carried the DQA1*0102, DQB1*0602 haplotype whereas this was only present in 26/30 patients, suggesting that the primary association is with HLA-DR and not -DQ. We also found a significant increase in HLA-DR4 (16/53 [30%] in patients compared with 7/55 [13%] in controls; pc=0.05). This study contributes a new point on the immunogenetic map of multiple sclerosis in Europe, confirming the primary DR15 association with multiple sclerosis in a previously unstudied population but again highlighting the importance of DR4 in Mediterranean peoples.