A growing body of literature links NOD2/CARD15 polymorphisms with a dysregulated innate immune response and susceptibility to diseases, including Crohn’s disease (Lesage et al., 2002), Blau syndrome (Kurokawa et al., 2003), early-onset sarcoidosis (Kapral, 1966), and graft-versus-host disease (Hoebe et al., 2005). Here, NOD2 is linked to graft versus host disease.