As detailed in the next part of this review, elevated levels of IL-17 are found in patients with autoimmune or inflammatory rheumatisms, such as RA, spondyloarthritis (SpA), systemic lupus erythematosus (SLE), or systemic sclerosis (SSc) [89–93], and in vivo studies demonstrated an important role of IL-17 in autoimmune arthritis by aggravating synovial inflammation and joint destruction [94, 95]. The gene discussed is IL17A; the disease is rheumatoid arthritis.