Blau syndrome (BS), first reported in 1985 as “juvenile systemic granulomatosis,” is a rare autosomal-dominant disease caused by NOD2/CARD15 gene mutations; the gene was individuated in 2001 on the locus 16q12.1-13, which also contains the genetic susceptibility region for Crohn's disease and early-onset sarcoidosis (EOS) [70, 71], and codifies for NOD2, a sensor of bacterial antigens which induces NF-κB activation [72]. This evidence concerns the gene NOD2 and Crohn disease.