Interestingly, BAFF-var is particularly frequent in Sardinia (26.5%), where the main study was conducted, with decreasing frequency when assaying from Southern (5.7%) to Northern European populations (1.8%). This high allele frequency in Sardinia allowed us to identify the association with multiple sclerosis at a genome-wide significance level using a relatively small sample set of about 3,000 patients and a similar number of controls.
