Polymorphisms of IL-6, IL-1α and IL1- receptor antagonist protein have been reported in patients with sJIA,31–33 and IL-18 polymorphisms have been reported in patients with AOSD.34 Macrophage migration inhibitory factor gene polymorphisms have also been observed in patients with sJIA35 and in those with AOSD.36 The gene discussed is MIF; the disease is adult-onset Still disease.