Crohn's disease is an inflammatory bowel disease that may affect any part of the gastrointestinal tract, causing a wide variety of symptoms. It can be categorized either by the specific tract region affected or by the behavior of disease as it progresses. It primarily causes abdominal pain, diarrhea, vomiting or weight loss, but may also cause complications outside the gastrointestinal tract such as skin rashes, arthritis, and inflammation of the eye. Crohn's disease, like many other chronic, inflammatory diseases, can cause a variety of systemic symptoms. Among children, growth failure is common. There is evidence of a genetic link to Crohn's disease, putting individuals with siblings afflicted with the disease at higher risk. In contrast to many other autoimmune diseases males and females are equally affected. The prevalence for Northern Europe has ranged from 27–48 per 100,000. Crohn's disease is more common in northern countries, and shows a higher preponderance in northern areas of the same country. Crohn's disease tends to present in two peaks, initially in the teens and twenties, with another peak incidence in the fifties to seventies, although the disease can occur at any age.
Many people with Crohn's disease have symptoms for years prior to the diagnosis.
The diagnosis of Crohn's disease can sometimes be challenging, and a number of tests are often required to assist the physician in making the diagnosis. The diagnostic tools include endoscopy/biopsy, radiology, nuclear scan and serology. It is important to be able to make a differential diagnosis between Crohn’s and ulcerative colitis as the two diseases have different prognosis and treatment strategies.
Serological tools have been developed over the last few years. A key marker of intestinal inflammation is calprotectin, a 36 kDa zinc-binding protein. Calprotectin is very abundant in neutrophil granulocytes protein where it constitutes more than 60% of total proteins in the cytosol.
Measurement of faecal calprotectin is useful as a noninvasive screening tool to differentiate functional from organic bowel pathology. A normal value of faecal calprotectin supports a clinical suspicion of irritable bowel syndrome. In Ulcerative colitis and Crohns disease faecal calprotectin correlates closely with disease activity and normalization of faecal calprotectin is a predictor of mucosal healing. Further, faecal calprotectin is a predictor of relapse in patients with inflammatory bowel disease. Slightly or moderately elevated values of calprotectin can be difficult to interpret and should be judged along with the patients’ clinical presentation. Other tests adjunct to calprotectin may be used in the diagnosis of IBD, such as antibodies against Sacharomyces cereviciae (ASCA) and pANCA. ASCA seems to be more associated with Crohn’s disease and pANCA is more prevalent in ulcerative colitis. Other ANCA reactivity may be seen in association with IBD.