Significantly increased frequencies of HLA-DR3 (36% vs 5%), HLA-DR7 (9% vs 4%), HLA-DR11 (36% vs 7%) and HLA-DRw53 (23% vs 5%) were observed in SSc-RA compared with RA patients (P < 0.05).
Furthermore, the sharing of the particular amino acid sequence: valine38 and phenylalanine67-lysine68-glutamic acid69-asparic acid70-arginine71, by DRB5*0102, DRB1*0802 and DR11 (associated with Caucasian PSS) also suggests a contribution of the sequence in HLA-DR molecules to the pathogenesis of PSS according to the shared epitope hypothesis.