HLA-DRB1 and systemic sclerosis: A significant increase in the frequency of alleles HLA-DPA1*02:01 (OR = 2.33, p = 1.0 × 10−8), DRB1*15:01 (OR = 2.40, p = 4.3 × 10−8) and DRB5*01:01 (OR = 2.38, p = 5.0 × 10−8) was also seen in ATA + relative to ATA − SSc, though these alleles did not show a significant association with risk of SSc, or either disease subtype, overall.