One of the following feature is true regarding Crohn’s disease
**Core Concept**
Crohn's disease is a type of inflammatory bowel disease (IBD) characterized by chronic inflammation of the gastrointestinal tract, often involving the terminal ileum and the beginning of the colon. The exact cause is unknown, but it is believed to result from an abnormal immune response to environmental factors and genetic predisposition.
**Why the Correct Answer is Right**
The correct answer involves understanding the pathophysiology of Crohn's disease. It is a T-cell mediated immune response, with a predominance of Th1 cells, which leads to the release of pro-inflammatory cytokines such as TNF-alpha and IL-12. This results in chronic inflammation, ulceration, and fibrosis of the affected bowel segment. The correct answer should reflect this underlying mechanism.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Crohn's disease is not primarily a B-cell mediated immune response. While B-cells may play a role, the primary immune response in Crohn's is driven by T-cells.
**Option B:** This option is incorrect because ulcerative colitis, not Crohn's disease, is characterized by a predominant Th2 response. Crohn's disease has a more complex immune response involving Th1 and Th17 cells.
**Option C:** This option is incorrect because while genetic predisposition is a risk factor for Crohn's disease, environmental triggers such as smoking and stress are also important. This option oversimplifies the etiology of the disease.
**Clinical Pearl / High-Yield Fact**
A key feature of Crohn's disease is the presence of "skip lesions," where areas of normal bowel are interspersed with diseased segments. This is in contrast to ulcerative colitis, which typically involves continuous inflammation of the colon.
**Correct Answer: D.**