Several polymorphisms localized in a region of chromosome 12 (12q13.3-12q14.1) have been associated with celiac disease, type 1 diabetes, rheumatoid arthritis and multiple sclerosis (MS). This study was focused in finding the causal variant in a sample set of 2876 MS patients and 2910 controls. We uncover a new polymorphism associated with the disease, exhibiting allele and orientation-dependent enhancer activity, potentially affecting the expression of four genes, amongst them the CYP27B1, involved in the last stage of vitamin D activation. We think this new functional genetic element may help in the fight against MS and other autoimmune diseases. (By Dr Antonio Alcina, http://jmg.bmj.com/content/early/2012/11/16/jmedgenet-2012-101085)