**Question:** Which of the following feature distinguishes Crohn's disease from Ulcerative colitis?

A. Involvement of terminal ileum and cecum only
B. Involvement of colon only
C. Involvement of any part of the gastrointestinal tract
D. Progressive nature

**Core Concept:**

Crohn's disease and ulcerative colitis are two types of inflammatory bowel diseases (IBD) that affect the gastrointestinal tract. Crohn's disease is characterized by transmural inflammation, meaning inflammation involves all layers of the intestinal wall. In contrast, ulcerative colitis is confined to the lining of the colon and rectum, known as the mucosa.

**Why the Correct Answer is Right:**

Crohn's disease (option C) stands out because it can affect any part of the gastrointestinal tract, including the terminal ileum, cecum, stomach, and small bowel, whereas ulcerative colitis (option A) is limited to the colon and rectum, with inflammation involving only the mucosa.

**Why Each Wrong Option is Incorrect:**

Option A is incorrect because it only involves the terminal ileum and cecum, which is a narrower range of affected areas compared to Crohn's disease. Option B is incorrect because ulcerative colitis affects the colon, not just the rectum. Option D is partially correct as both diseases are progressive, but it does not differentiate between the two conditions.

**Clinical Pearl:**

The distinguishing feature between Crohn's disease and ulcerative colitis lies in their distribution. Crohn's disease can affect any part of the gastrointestinal tract, while ulcerative colitis is confined to the colon and rectum, involving only the mucosa. Understanding this key difference helps in differentiating between the two conditions, which can guide diagnosis and treatment decisions.