HLA-DRB1 and polyarticular arthritis: Although genetic and molecular differences between the oligoarticular and polyarticular subtypes may be limited, systemic JIA patients present substantial diversity, exhibiting not only clinical systemic inflammatory features similar to those of autoinflammatory diseases, but also a unique transcriptional profile and genetic architecture, not sharing heritable risk factors with oligo or polyarthritis, even within the HLA region (e.g. it shows association with the HLA-DRB1*11 haplotype), as determined by transcriptomic and large-scale genomic studies [39, 40].