Etiology of Crohnʹs disease: the role of Mycobacterium avium paratuberculosis

Crohnʹs disease is a chronic inflammatory bowel disease characterized by transmural inflammation and granuloma formation. Several theories regarding the etiology of Crohnʹs disease have been proposed, one of which is infection with Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis), which causes a similar disease in animals, and is present in the human food chain. Considerable evidence supports the presence of M. paratuberculosis in the intestinal tissues of many patients with Crohnʹs disease including culture, detection of homologous mycobacterial DNA, detection of the mycobacterial insertion sequence IS900 by both PCR and in situ hybridization in tissues, and a serologic immune response to recombinant M. paratuberculosis antigens. Despite this evidence, and our personal belief that M. paratuberculosis is a cause of Crohnʹs disease, widespread acceptance of this hypothesis will require evidence that specific anti-mycobacterial chemotherapy will cure the disease.