HLA-DRB1 and rheumatoid arthritis: We extended the sequences for four DRB1*04 alleles and identified novel intronic variants for five DRB1*04 alleles (Table S7) that could be separated into three rheumatoid arthritis (RA) categories based on the previous results of a case-control study using 1480 patients and 800 healthy controls in the Japanese population (47).