Genetic variations in genes encoding for autophagy-related 16-like 1 (ATG16L1), Unc-51-like autophagy-activating kinase (ULK1), immunity-related GTPase family M protein (IRGM) and nucleotide-binding oligomerization domain-containing protein 2 (NOD2) have all been associated with Crohn's disease. The gene discussed is IRGM; the disease is Crohn disease.