HLA-DRB1 and arthritic joint disease: The study of the relationships between the SLE risk alleles and clinical sub-phenotypes led to the finding that certain lupus manifestations are more dependent on the presence of multiple risk alleles, while others are more strongly associated with a single variant, for example, renal disease more significantly associated with HLA-DRB1, and arthritis with the protective allele of ITGAM [42].