European Union (European Commission, 2000), these data are dealt with in more general terms.

CROHN’S DISEASE

Crohn’s disease is an inflammatory disorder of the intestine of unknown cause. The disease is chronic, and patients tend to remit and relapse. Symptoms include general malaise, chronic weight loss, abdominal pain, and diarrhea. It is a life-long disease that has no cure. CD usually begins early in life, with peak incidence between the ages of 16 and 25, but it can occur in early childhood or later in life. Although the disease can occur in any portion of the gastrointestinal tract, it has a predilection for the terminal ileum. The three most common patterns of disease are the involvement of the terminal ileum and cecum, the ileum alone, and the colon alone. The disease is treated with various agents—aminosalicylates, corticosteroids, azathioprine, anti-TNF antibody, antibiotics—to inhibit the inflammatory response in the intestine. Unfortunately, therapy is imperfect and relapses are common. The disease can be complicated by perforation, abscess formation, fistula formation, strictures, and intestinal obstruction. Several of those complications can require surgery in which sections of the bowel are removed. Some patients suffer many intestinal resections which leave them with a “short bowel” (insufficient small bowel to maintain hydration, nutrition, and health). Those patients are sustained with total parenteral nutrition—intravenous feeding with a specialized formulation.

Etiology of Crohn’s Disease

The cause or causes of Crohn’s disease are unknown. Prominent hypotheses include an aberrant or autoimmune host inflammatory response to undefined antigens, infectious etiologies including Map, and aberrant immune response to a specific infectious agent. There is conflicting evidence for and against each of these proposed pathogenetic mechanisms for Crohn’s disease. As it is currently understood, the disease could, in fact, be more than one malady (Gilberts et al., 1994; Mishina et al., 1996). If this is true, then the existing conflicts in interpretation of evidence for causation may be resolved by clear categorization of Crohn’s disease into multiple syndromes having distinct etiologies. If Map is involved in some cases of Crohn’s disease, it does not appear to be a simple case of infection by an agent in a susceptible host. The generally favorable response of Crohn’s patients to profound immunosuppression and/or bone marrow transplantation supports the notion that immune dysfunction or dysregulation is an important element of the disease (James, 1988; Kashyap and Forman, 1998; Lopez-Cubero et al, 1998; Soderholm et al., 2002; Yoshida et al, 1996). This suggests that if Map is involved at all, it is as a result of an aberrant host immune response to the presence of the agent.

In addition to Map, various other causes of Crohn’s disease have been proposed: chronic ischemia and microinfarction, persistent measles infection, chronic viral infection, infection with pathogenic E. coli, abnormal response to a



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