HLA-DRB1 and rheumatoid arthritis: The presence of two HLA-DRB1*04 SE alleles was significantly associated with ExRA overall (OR 1.79, 95% CI 1.04–3.08), Felty's syndrome (OR 2.63, 95% CI 1.04–6.63), and vasculitis (OR 2.44, 95% CI 1.22–4.89) compared with patients with RA who lacked these manifestations.