PDCD1 and systemic lupus erythematosus: Moreover, because one-third of first-degree relatives of patients with primary pSS suffer from other autoimmune diseases [10] and given that BAFF over-expression was also demonstrated in RA [11] and SLE [12], BAFF could be a good candidate gene in the predisposition to multiple autoimmune diseases, as was recently observed for the genes encoding PTPN22, RUNX1, PDCD1 and CTLA4 [13].