NOD2 and Crohn disease: Crohn's disease shows genetic susceptibility (e.g., NOD2 variants) and MAP detection, supporting impaired clearance of intracellular mycobacteria.<h4>Conclusions</h4>Overall, evidence supports a bidirectional relationship: mycobacterial antigens can initiate or amplify autoimmunity via molecular mimicry and chronic stimulation, while autoimmune biology and iatrogenic immunosuppression increase susceptibility to infection.