Update on Crohn's disease: a polymorphic entity.

Crohn's disease is a chronic transmural inflammatory disease that most commonly affects the intestinal wall, but may also occur in any part of the gastrointestinal tract; its incidence is higher in industrialized countries, urban areas and upper socioeconomic classes. Various environmental risk factors have been associated with the pathogenesis of Crohn's disease and possible infectious agents (viruses, bacteria, yeasts) have also been considered. However, none of these factors alone leads to the development of the disease, which may occur only when there is a genetic predisposition and/or an abnormal function of the intestinal immune system. Histopathology demonstrates mucosal hyperemia, with small superficial ulcers in mild forms of the disease; in moderate-to-severe forms, serpiginous ulcerations demarcating areas of edematous mucosa produce the characteristic "cobblestone" appearance. The earliest microscopic lesions appear as neutrophil-mediated cryptic damage, with the formation of focal cryptic abscesses and granulomas throughout the layers of the intestinal wall. In addition to weight loss, patients mainly refer chronic diarrhea and recurrent right iliac fossa abdominal pain. Extraintestinal manifestations include ocular or articular complications. There are several drugs classes available for treating Crohn's disease, but the therapeutic approach depends on the clinical picture and differs from patient to patient. The broad clinical and the histopathological features of Crohn's disease make it a highly polymorphic entity. Diagnostic tests and a thorough knowledge of its various aspects are essential for guiding diagnosis and treatment.