IL17F and histiocytic sarcoma: This is consistent with the elevations in the serum and tissue levels of IL-17A, IL-17F, and other isoforms of IL-17 in a variety of autoimmune and immune-mediated inflammatory diseases (IMIDs), such as lupus, PsO, PsA, multiple sclerosis, rheumatoid arthritis (RA), axSpA, scleroderma, and hidradenitis suppurativa (HS) [3].