NOD2 and Blau syndrome: An example is the study of patients with gain-of-function mutations in NOD2 demonstrating a genetic and molecular phenotype causing Blau syndrome (and a presenting phenotype of early onset sarcoidosis), who may present with tenosynovitis, rash and uveitis.82 The protein product of NOD2 is an innate sensing receptor, which after ligation leads to cytokine production and inflammation through NFkB.