We previously described the biochemical principle of a functional assay that may support diagnosis of FMF.24 The Pyrin inflammasome pathway is activated by toxin A from Clostridium difficile, resulting in the release of significant amounts of proinflammatory cytokines IL-1β and IL-18 from intoxicated monocytes and macrophages. The gene discussed is IL1B; the disease is familial Mediterranean fever.