## Correct Answer: B. Celiac disease Celiac disease is a **CD8+ T-cell mediated autoimmune enteropathy** triggered by gluten ingestion in genetically predisposed individuals (HLA-DQ2/DQ8). The histopathological triad—**crypt hyperplasia, villous atrophy, and increased intraepithelial lymphocytes (predominantly CD8+)**—is pathognomonic for celiac disease and reflects the autoimmune destruction of the small intestinal mucosa. The CD8+ cytotoxic T cells target tissue transglutaminase (tTG)-deamidated gluten peptides, causing mucosal inflammation and flattening of villi. This architectural damage leads to **reduced absorptive surface area**, resulting in malabsorption of fats, carbohydrates, proteins, iron, calcium, and fat-soluble vitamins. The clinical presentation—malabsorption, chronic diarrhea, and poor appetite—correlates directly with this mucosal injury. In India, celiac disease is increasingly recognized, particularly in North Indian populations, and presents with similar GI symptoms alongside extraintestinal manifestations (anemia, dermatitis herpetiformis, osteoporosis). Marsh classification grades this histology as Type 3 (partial to total villous atrophy), which is diagnostic when combined with positive serology (tissue transglutaminase IgA antibodies) and clinical response to a gluten-free diet. ## Why the other options are wrong **A. Chronic pancreatitis** — Chronic pancreatitis causes **pancreatic insufficiency and malabsorption**, but the duodenal mucosa remains histologically normal. There is no villous atrophy, crypt hyperplasia, or CD8+ lymphocytic infiltration in the lamina propria. Pancreatic disease affects intraluminal digestion (enzyme deficiency), not mucosal architecture. The biopsy findings are entirely inconsistent with pancreatic pathology. **C. Whipple's disease** — Whipple's disease (caused by *Tropheryma whipplei*) presents with malabsorption and diarrhea, but the **pathognomonic finding is foamy macrophages in the lamina propria** filled with PAS-positive, diastase-resistant organisms—not CD8+ lymphocytes. Villous atrophy is typically absent or mild. The disease predominantly affects middle-aged men and is rare in India. The CD8+ infiltrate and villous architecture described here are not characteristic of Whipple's disease. **D. Environmental enteropathy** — Environmental enteropathy (EE) is a **subclinical mucosal injury** associated with poor sanitation and repeated enteric infections, common in low-income countries including India. While EE shows villous blunting and increased intraepithelial lymphocytes, it typically presents with **mild histological changes and asymptomatic malabsorption** in children. The degree of crypt hyperplasia and villous atrophy described, combined with symptomatic malabsorption in a 20-year-old, is more consistent with celiac disease. EE is usually self-limited and does not require gluten avoidance. ## High-Yield Facts - **Celiac disease histology**: villous atrophy + crypt hyperplasia + CD8+ intraepithelial lymphocytes (Marsh Type 3) = diagnostic on duodenal biopsy - **CD8+ T-cell mediated** autoimmune response to tTG-deamidated gluten peptides in HLA-DQ2/DQ8 individuals - **Malabsorption mechanism**: reduced absorptive surface area from mucosal flattening → fat, carbohydrate, protein, iron, and vitamin deficiencies - **Serology**: tissue transglutaminase (tTG) IgA antibodies are sensitive and specific; endomysial antibodies (EMA) are highly specific - **Indian context**: increasing prevalence in North India; often misdiagnosed as tropical sprue or irritable bowel syndrome - **Gold standard diagnosis**: duodenal biopsy showing Marsh Type 3 histology + positive serology + clinical response to gluten-free diet ## Mnemonics **MARSH Classification (Celiac Histology)** Type 0 = Normal | Type 1 = Increased IELs only | Type 2 = IELs + crypt hyperplasia | Type 3 = Villous atrophy (partial/subtotal/total) | Type 4 = Hypoplastic. **Type 3 = diagnostic for celiac disease.** **CD8+ Clue for Celiac** **CD8+ cells in lamina propria = cytotoxic T-cell mediated autoimmunity.** Remember: Celiac = CD8+ (cytotoxic), not CD4+ helper cells. This distinguishes it from other enteropathies. ## NBE Trap NBE may pair "malabsorption + diarrhea" with chronic pancreatitis to trap students who focus only on clinical symptoms and ignore the **specific histological finding of CD8+ lymphocytes and villous atrophy**, which are mucosal, not pancreatic, features. ## Clinical Pearl In Indian clinical practice, celiac disease is often missed because it is confused with tropical sprue or attributed to poor sanitation. The **key discriminator is the duodenal biopsy showing CD8+ lymphocytes and villous atrophy**—not just clinical symptoms. A gluten-free diet trial confirms diagnosis when serology is positive and histology is consistent. _Reference: Robbins & Cotran Pathology Ch. 17 (Small Intestine); Harrison's Principles of Internal Medicine Ch. 297 (Celiac Disease)_
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