Crohn disease: Uncertainty about the etiologic role of Mycobacterium paratuberculosis.

In recent years, attention and discussion have been devoted to the possible association of Mycobacterium paratuberculosis, agent of paratuberculosis i n ruminants, with Crohn's disease. Both diseases, which affect young adults , are characterized by chronic granulomatous lesions, typically concentrate d in the terminal ileum, and clinical signs of enteritis and weight loss. T he etiology of Crohn's disease is unknown but genetic, environmental, immun ological and microbiological influences, in various combinations, have been suggested. Human exposure to M. paratuberculosis may occur essentially fro m a fecal contamnation (drinking water, milk...). This association between Crohn's disease and paratuberculosis has been shown but a causal relationsh ip remains to be demonstrated.