A study of families from southern Tunisia affected by general pustular psoriasis uncovered the genetic cause of their disease: a mutation affecting the function of the interleukin-36–receptor antagonist. Psoriasis is a chronic inflammatory skin disease affecting 2 to 3% of persons of European descent. 1 Psoriasis vulgaris, the most common form of the disease, accounts for 80% of cases and has a strong, albeit complex, genetic component. 2 Numerous chromosomal loci have been implicated in genomewide association studies, but analyses of these loci have yielded only a few candidate genes, which mediate inflammatory cytokine signaling and adaptive immune responses. 3 – 5 The disease follows mendelian transmission in a small minority of families. Generalized pustular psoriasis is a life-threatening, multisystemic inflammatory disease involving repeated flare-ups of sudden onset, which are characterized by . . .