The investigation of Portuguese patients also identified the HLA-DRB1*01 (OR = 1.79) and HLA-DRB1*04 (OR = 2.81) polymorphisms as predisposing one to RA, and the HLA-DRB1*13 allele as protective [18]. The gene discussed is HLA-DRB1; the disease is rheumatoid arthritis.