A 32-year-old woman with a 6-year history of ulcerative colitis presents with abdominal pain and bloody diarrhea. Colonoscopy reveals continuous mucosal inflammation from the rectum extending to the sigmoid colon. Regarding the extraintestinal manifestations of ulcerative colitis, all of the following are true EXCEPT:

Question

Accepted Answer

C. Pyoderma gangrenosum is a pathognomonic skin lesion that occurs exclusively in ulcerative colitis and never in Crohn's disease. ## Extraintestinal Manifestations of Ulcerative Colitis

### Classification and Frequency

**Key Point:** Extraintestinal manifestations (EIMs) occur in 10–15% of ulcerative colitis patients and may precede, accompany, or follow bowel disease.

### Comparison of EIMs in IBD

| EIM | UC Frequency | Crohn's Frequency | Activity Correlation | HLA Association |
|-----|--------------|-------------------|----------------------|-----------------|
| **Erythema nodosum** | 2–4% | 2–4% | Yes (active disease) | — |
| **Pyoderma gangrenosum** | 0.5–2% | 0.5–2% | Variable | — |
| **Primary sclerosing cholangitis** | 1–4% | <1% | **No** (independent) | — |
| **Ankylosing spondylitis** | 1–3% | 1–3% | No | HLA-B27 |
| **Peripheral arthritis** | 4–6% | 4–6% | Yes (active disease) | — |
| **Uveitis** | 0.5–1% | 0.5–1% | Variable | — |

### Analysis of Options

**Option 1 (Erythema nodosum):** ✓ Correct — Occurs in 2–4% of UC patients; presents as painful, tender nodules on the shins and ankles; **correlates with disease activity** and typically resolves with treatment of the underlying IBD.

**Option 2 (Primary sclerosing cholangitis):** ✓ Correct — Associated with UC in 1–4% of cases; **crucially, PSC may progress independently** of bowel disease activity and may even develop or worsen after colectomy. This is a key distinguishing feature from other EIMs.

**Option 3 (Ankylosing spondylitis):** ✓ Correct — Occurs in 1–3% of UC patients; **HLA-B27 positive in the majority** (70–90%); does **not correlate** with bowel disease activity.

**Option 4 (Pyoderma gangrenosum):** ✗ **WRONG** — This option claims pyoderma gangrenosum is **pathognomonic for ulcerative colitis and never occurs in Crohn's disease**. This is **factually incorrect**. Pyoderma gangrenosum occurs in both UC (0.5–2%) and Crohn's disease (0.5–2%) with similar frequency. It is **not pathognomonic** for either disease and can also occur in other systemic conditions (rheumatoid arthritis, malignancy, etc.).

**High-Yield:** **Pyoderma gangrenosum is NOT specific to UC** — it occurs in both Crohn's disease and UC, and also in non-IBD conditions. This is a common NEET PG trap.

**Clinical Pearl:** The presence of pyoderma gangrenosum in a patient with IBD does not help differentiate between UC and Crohn's disease; other features (distribution, depth of inflammation, granulomas) are required.

Answer

A. Ankylosing spondylitis occurs in 1–3% of patients and is HLA-B27 positive in the majority of cases

Answer

B. Primary sclerosing cholangitis (PSC) is associated with ulcerative colitis in 1–4% of cases and may progress independently of bowel disease activity

Answer

D. Erythema nodosum occurs in 2–4% of patients and typically correlates with disease activity

Explanation

Extraintestinal Manifestations of Ulcerative Colitis

Classification and Frequency

Comparison of EIMs in IBD

Analysis of Options

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EIM	UC Frequency	Crohn's Frequency	Activity Correlation	HLA Association
Erythema nodosum	2–4%	2–4%	Yes (active disease)	—
Pyoderma gangrenosum	0.5–2%	0.5–2%	Variable	—
Primary sclerosing cholangitis	1–4%	<1%	No (independent)	—
Ankylosing spondylitis	1–3%	1–3%	No	HLA-B27
Peripheral arthritis	4–6%	4–6%	Yes (active disease)	—
Uveitis	0.5–1%	0.5–1%	Variable	—