Blau syndrome is a rare, autosomal-dominant, autoinflammatory disorder characterized by granulomatous arthritis, uveitis, and dermatitis. Genetics studies have shown that the disease is caused by single nonsynonymous substitutions in NOD-2, a member of the NOD-like receptor or NACHT–leucine-rich repeat (NLR) family of intracellular proteins. Several NLRs function in the innate immune system as sensors of pathogen components and participate in immune-mediated cellular responses via the caspase 1 inflammasome. Mutations in a gene related to NOD-2, NLRP3, are responsible for excess caspase 1–dependent interleukin-1β (IL-1β) in cryopyrinopathies such as Muckle-Wells syndrome. Furthermore, functional studies demonstrate that caspase 1–mediated release of IL-1β also involves NOD-2. The aim of this study was to test the hypothesis that IL-1β may mediate the inflammation seen in patients with Blau syndrome.