Inflammatory Bowel Disease

The incidence of inflammatory bowel disease (IBD) has increased in recent years.1

Approximately 1.6 million Americans have IBD,1,2 which is comprised of 2 major types: ulcerative colitis (UC), characterized by continuous, mucosal inflammation limited to the innermost lining of the colon and rectum, and Crohn’s disease (CD), defined by patchy, transmural inflammation which can affect any part of the gastrointestinal (GI) tract, from the mouth to the perianal area.1,3,4

Inflammatory bowel disease illustration


Population-based studies in the U.S. suggest that the incidence of IBD is most common in patients aged 15 to 35 years.1 IBD can also present in childhood, including up to 20% of children who are diagnosed before the age of 10 years.5 It is more common in Whites (vs other racial groups) and in adults, UC is more common in males.1,6


Symptoms of IBD depend on the disease location, and can range from mild to moderate to severe.2,4 Diarrhea and rectal bleeding are characteristic with UC. Patients can experience weight loss and fever (although it can be less common than with CD), and abdominal pain varies depending on the patient. For CD, weight loss, fever, and abdominal pain are more predominant, although these patients can also experience diarrhea and rectal bleeding.4

Irritable bowel syndrome (IBS), the most common GI condition diagnosed by gastroenterologists, may be mistaken for IBD since IBS symptoms may mimic those seen in a patient with mild IBD, but history and additional diagnostic tests can help rule it out of the differential diagnosis.7 Endoscopy combined with biopsies of the affected area(s) of the GI tract will also establish the diagnosis and differentiate between UC and CD.4,8


The etiology of IBD most likely involves a complex interaction between genetic and environmental factors, microbiome, and the immune system.3,4 T cells, which are activated by antigen-presenting cells in the peripheral lymphoid tissue, migrate to the site of inflammation and play a role in recruitment and activation of additional inflammatory cells in the GI tract.9,10

Navigating IBD

IBD is a chronic disease, with significant impact on a patient’s general health.3 While the Crohn’s Disease Activity Index (for CD) and Mayo Score (for UC) are the most frequently used instruments for scoring and monitoring disease activity in clinical trials, researchers are working to improve the measures of disease activity and severity through assessment of impact of disease on the patient, disease burden, and disease course, including structural damage with a goal of improving disease management for patients.11