Different from “classic” sarcoidosis (usually without hilar lymphadenopathy and interstitial fibrosis) and typical of preschool age are the granulomatous auto-inflammatory diseases including the familial form known as Blau syndrome (BS, OMIM 186580) and the sporadic form known as early-onset sarcoidosis (EOS, OMIM 609464); both are caused by mutations in the NOD2/CARD15 gene and characterized by the clinical triad of granulomatous recurrent panuveitis, dermatitis, and symmetric arthritis with large, boggy synovial effusions and tenosynovial cysts particularly affecting the wrists and ankles. The gene discussed is NOD2; the disease is Blau syndrome.