HLA-DRB1 and systemic sclerosis: A significant association with susceptibility to SSc with ACA was found for the DRB1*01:01 and DRB1*10:01 alleles (P = 0.0001, Pc = 0.0042, OR 2.52, 95%CI 1.58–4.01; P = 0.0003, Pc = 0.0097, OR 11.17, 95%CI 2.42–51.48, respectively, S2 Table).