Crohn disease is a disease of chronic inflammation in the gastrointestinal tract that can involve anywhere from the mouth to the anus. It is characterized by transmural inflammation and often noncaseating granulomas. The etiology is unclear, but it is likely triggered by a combination of genetic and environmental factors, with mucosal injury caused in part by immune activation against healthy intestinal microbiota.

Symptoms from Crohn disease can vary considerably, due to location but also to the severity of disease involvement. Patients may present with abdominal pain, bloody or nonbloody diarrhea, weight loss or malnutrition, fistulas, abscesses (often perianal), dysphagia, or oral ulcerations. Additionally, Crohn disease has many extraintestinal manifestations that can at times be the presenting symptoms. These manifestations can involve joints, skin, eyes, vasculature, the lungs, or the kidneys.

Chronic inflammation from Crohn disease can lead to fistula and stricture formation, which predispose to small and large bowel obstructions, infections secondary to fistula tracts, and malnutrition as a result of longstanding intestinal inflammation. These complications result in much of the morbidity from Crohn disease, highlighting the importance of achieving and sustaining deep remission as a primary goal of treatment.

Crohn disease presents most typically in the second to fourth decades of life, with a slight female predominance. While no clear genetic mutation is linked to the development of Crohn disease, there are many genetic mutations that are associated with Crohn disease. For unclear reasons, Crohn disease is more prevalent at higher latitudes and in certain patient populations, namely individuals of Ashkenazi Jewish descent and individuals of Northern European descent in the United States.

Crohn disease is a chronic disease with many pharmacologic options that can be used depending on the severity of symptoms and on radiographic and endoscopic findings. Many patients are able to achieve remission, although the disease is progressive in nature and characterized by disease flares.