NOD2 and Blau syndrome: This has been assumed to be the case in the auto-inflammation known as Blau syndrome wherein mutations usually present in the nucleotide oligomerization domain of the <i>CARD15</i> gene encoding NOD2 result in widespread granulomatous inflammation, seemingly in the absence of NOD2 stimulation by its canonical ligand, muramyl dipeptide (MDP); moreover, despite such lack of ligand stimulation, NOD2 bearing a Blau mutation is thought to cause inflammation by initiating conventional downstream signaling that ultimately results in NF-κB activation.