STAT4 and systemic sclerosis: Multiple reports of well powered candidate gene association and replication studies, together with the first genome-wide association study (GWAS) in this disease have led to the establishment of the Major histocompatibility complex (MHC), STAT4, IRF5, BLK, BANK1, TNFSF4 and CD247 as SSc susceptibility genes [2]–[15].