The role of mycobacteria in Crohn's disease

Crohn's disease (CD) was first described in 1932 as a chronic inflammation of the terminal ileum. CD affects primarily young adults and the elderly, but can occur at any age. CD is one of a group of inflammatory bowel diseases (IBD) that also includes ulcerative colitis (UC). Although some studies suggest a hereditary predisposition, CD is thought to have a multifactorial aetiology involving genetic, environmental, microbial and immunological factors. A specific aetiological agent of CD has not been identified. The inflammatory nature of the disease has led to studies focusing on imbalance of the immune system, resulting from either an inherited disorder or as a response to microbial antigens in the gut. Studies based on phenotype and genotype have shown that M. paratuberculosis clusters with the MAI complex. This species colonises the intestinal mucosa of ruminants causing Johne's disease (JD). CD and JD share clinical symptoms. Both are chronic granulomatous diseases of the gut affecting nutrient absorption and frequently affecting the young.