A novel immunomodulatory cytokine IL-41 (synonyms: IL-41, Cometin, Subfatin, Meteorin (Metrn)-like, or Meteorin-β) is decreased in inflammatory bowel disease 7, Graves' disease 8 and is elevated in Kawasaki disease 9, gout 10, psoriatic arthritis 11 and RA 12,13. The gene discussed is METRNL; the disease is psoriatic arthritis.