NLRC4 and macrophage activation syndrome: Although serum IL-18 elevation has been previously reported associated with macrophage activation syndrome (MAS) in systemic juvenile idiopathic arthritis, adult-onset Still’s disease, and NLR family CARD domain containing 4 (NLRC4) inflammasomopathy autoinflammation (7, 8), recent study revealed that PAPA syndrome is associated with chronic and unopposed elevation of serum IL-18 levels without risk of MAS (9).