Rilonacept (Arcalyst®), a soluble decoy receptor composed of the extracellular domains of IL-1R1 and IL-1RAcP fused to a human IgG1 Fc domain, is an interleukin-1 blocker indicated for the treatment of CAPS, namely, Familial Cold Autoinflammatory Syndrome (FCAS) and Muckle–Wells Syndrome (MWS) in adults and in children at least 12 years old. The gene discussed is IL1R1; the disease is familial cold autoinflammatory syndrome.