Microscopic colitis (MC) is a name used to describe a chronic diarrheal syndrome that is caused by inflammation in the large intestine. It is called “microscopic” colitis because the inflammation can be detected only with a microscope. During an endoscope procedure (colonoscopy or sigmoidoscopy), the colon looks normal. The presence or absence of a specific feature within the colonic inflammatory process as seen under the microscope (thickened collagen under the surface of the biopsy) has led to use of two other names for this syndrome: collagenous colitis and lymphocytic colitis. The symptoms and treatment of this syndrome are identical, regardless of whether the collagen in the biopsy is thick or normal.
The typical patient is a middle-aged woman; but it is seen in men, children as young as six and older people also. Possible initial misdiagnoses include stress, gastroenteritis, celiac sprue, lupus, or irritable bowel syndrome (IBS). It’s not unusual for diagnosis to take several years, since microscopic colitis is the form of inflammatory bowel disease least familiar to doctors and often the last considered.
There does not seem to be an association with Crohn’s disease, ulcerative colitis, or cancer. It does not appear to be contagious. Some patients report a close family member with the same diagnosis or with similar intestinal symptoms, and it appears there may be a hereditary tendency to get microscopic colitis.
Certain foods, especially high fiber, fat, milk products, spices, wheat and/or uncooked fruit and vegetables, may aggravate it. But, some patients tolerate any foods — even when quite ill.
Approximately half of the patients with microscopic colitis report a sudden onset. They can pin down the exact day and location that symptoms started, often triggered by an initial bout with dysentery, giardia, or an undiagnosed intestinal illness.
One theory is that the inflammatory response is caused by a bacterium or a bacterial toxin. Another theory suggests this is an autoimmune disease, although that hasn’t been conclusively established. A third suggests that non-steroidal anti-inflammatory drugs (NSAIDs, such as aspirin or ibuprofen) might be responsible or aggravate the symptoms in individuals predisposed to the disease by another mechanism. It may well turn out to be a combination of several of these factors.
This illness can come and go, with or without treatment, making it difficult to assess the effect of any treatment plan.