Inflammatory bowel disease (IBD) describes a group of chronic conditions that includes Celiac Disease, Crohn's Disease, ulcerative colitis, microscopic colitis (collagenous colitis and lymphocytic colitis), ‘indeterminate colitis’ and more. These conditions may overlap and some are better understood than others. While Celiac Disease may be controlled by avoiding gluten and certain grains, for example, the exact causes of Crohn’s Disease are debated and research continues.
Described first in 1932 by American doctor Burrill Bernard Crohn, Crohn’s Disease (CD) is a chronic ‘autoinflammatory’ condition of the small intestine and colon although any part of the digestive system may be affected. While Crohn's is an immune-related disease, ongoing research suggests that it may not be an autoimmune disease – the immune system is not being triggered by the body itself.
The symptoms of Crohn’s Disease include diarrhea, abdominal pain, weight loss, fever, skin rashes, anemia and more. CD can fluctuate between periods of acute symptoms and remission. According to the CDC, an estimated 1.3% of US adults (3 million) reported being diagnosed with IBD (either Crohn's disease or ulcerative colitis).
…up to 25% of individuals with IBD develop extraintestinal effects, including joint inflammation, skin lesions [called pyoderma gangrenosum], eye complications, and osteopathy.
CD is believed to be caused by a combination of environmental, immune, and bacterial factors in genetically susceptible individuals. New research suggests that the chronic inflammation in CD results from the body’s defence of the gastrointestinal tract targeting, possibly, microbial antigens. In this regard, the “cold-chain hypothesis”, discussed in a 2020 article, identifies specific bacteria:
The development of industrial and domestic refrigeration has led to frequent exposure of human populations to bacteria capable of growing in the cold. These bacteria, at low levels of exposure, particularly those of the genus Yersinia, are believed to induce exacerbated inflammation of the intestine in genetically predisposed subjects.
Studies also indicate that CD may begin after a bout of gastroenteritis:
Crohn's disease frequently occurs after infectious gastroenteritis, has a distinct mucosal flora (dysbiosis), and increased numbers of intramucosal bacteria often featuring adhesive species and thus efforts to identify a causative infectious agent continue.
Lifestyle, diet, pharmaceutical use and physical inactivity that may alter bowel flora diversity have all been noted as addition risk factors for the disease. The most closely studied risk factor for CD, however, is early tobacco smoking which can also make the disease more severe. Tobacco smoke contains hundreds of chemicals harmful to the digestive system.