The presence of two HLA-DRB1*04 alleles encoding the shared epitope (SE) was associated with ExRA (overall odds ratio 1.79, 95% confidence interval 1.04-3.08) and with rheumatoid vasculitis (odds ratio 2.44, 95% confidence interval 1.22-4.89).
The risk of developing RV with minor skin vasculitis (i.e., purpura or petechiae) was 10-20-fold increased in patients with DRB1*04, in particular in those homozygous for DRB1*04, and also in those with DRB1*0401.
In the light of associations previously described between DR4, DQw7, the C4B null allele and Felty's syndrome, and between Dw14, the C4A null allele and rheumatoid vasculitis, we have looked for associations between these and other DRB1, DQB, DQA and C4 encoded variants, and articular disease severity assessed radiologically in 119 subjects with RA but without major extra-articular features.