Crohn disease (CD) is a chronic transmural inflammatory disease of the gastrointestinal tract, mainly characterized by abdominal pain, diarrhea and various digestive or non-digestive complications, with alternating eruptions and remissions.
CD is more common in northwestern countries where the incidence ranges between 1 and 10/100,000, and a prevalence of approximately 1-0.5/1,000. Thus, in Europe and North America, CD is not considered as a rare disease.
CD is generally diagnosed in the 2nd or 3rd decade, but an unnoticed earlier onset is possible given the insidious and unspecific manifestations of the disease. The clinical picture is highly variable depending on the patient and the course of the disease, characterized by eruptions alternating with remission periods. Disease severity is assessed by a clinical score called the CD Activity Index (CDAI). Symptoms of the flare-up are pallor, cachexy, weight loss, fever, abdominal pain, chronic or nocturnal diarrhea with blood, mucus or pus, abdominal mass or tenderness, perianal fissures, fistula (between intestine and other digestive or uro-genital organs or skin) or abscess. Malabsorption may induce anemia, cholelithiasis, nephrolithiasis, failure of growth, or delayed development of secondary sex characteristics. Extra-intestinal manifestations, which can sometimes be observed before the intestinal ones, include inflammation of the eye, arthritis, erythema nodosum, pyoderma gangrenosum (see this term) and primary sclerosing cholangitis (see this term). Despite phenotypical heterogeneity based on disease location, several clinical patterns have been defined (inflammatory, fibrostenotic or fistulizing). They can orientate patient management. In most cases, intestinal inflammation lies in the ileum and the colon, but can also be limited to the colon, or more rarely, and particularly in young patients, to the jejunum and the ileum. Clinical consequences are typically rectal bleeding, perianal and extraintestinal (skin and joints) complications and stenoses, bacterial overgrowth and protein or vitamin-losing enteropathy seen in jejunoileitis.
Etiology of CD is unclear as many environmental factors, a genetic predisposition and a triggering event seem to be required for the disease to develop. Until now several loci have been associated to the disease, but no Mendelian mode of inheritance has been observed.
A single gold standard for the diagnosis of CD is not available. Diagnosis is based on physical examination, radiology and histopathological examination of multiple intestinal biopsies, revealing discontinuous or granulomatous intestinal inflammation.
There is no specific clinical sign for CD diagnosis, thus differential diagnosis is wide, and predominantly includes ulcerative colitis (see this term). Microbiological investigations are needed to exclude infectious diarrhea.
CD is neither medically nor surgically curable, but therapeutic approaches focus on symptomatic treatments and improvement of quality of life. Mucosal healing is a new therapeutic goal that could lead to long term remission. For induction or maintenance of remission, medication may include aminosalicylates (5-ASA), antibiotics, corticosteroids (prednisolone, budesonide), immunosuppressive drugs and antibodies directed against TNF (infliximab or adalimumab). Surgical resections are usually reserved for complicated disease (stenosis and/or perforation) or for dysplasia or cancer.
Overall prognosis is good but morbidity is still significant, especially during flare-ups.
Last update: January 2013