IL18 and macrophage activation syndrome: Mutations in the NOD of NLRC4 result in autoinflammation, with a spectrum of clinical manifestations ranging from cold-induced urticaria to life-threatening macrophage activation syndrome (MAS) with severe enterocolitis.6, 7, 8, 9, 10 NLRC4-associated autoinflammatory disorders (NLRC4-AIDs) are characterized by high levels of free IL-18 in the serum of patients, distinguishing it from other monogenic inflammasomopathies, such as Familial Mediterranean Fever or Cryopyrin Associated Periodic Syndrome.