HLA-DRB1 and rheumatoid arthritis: For example, the presence of a histidine at the same HLA-DRB1 position confers the highest risk for RF+polyJIA, consistent with the association reported in adult seropositive RA.7 In addition, the amino acid at position 58 of HLA-DRB1 has been shown to be a specific risk factor for sJIA.10