A 52-year-old man from Delhi presents with chronic epigastric pain, bloating, and reduced appetite for 6 months. Upper endoscopy reveals multiple gastric ulcers with surrounding erythema. Histology shows loss of parietal cells and extensive intestinal metaplasia. Which of the following is the most common cause of this histological pattern?

Explanation

## Classification and Epidemiology of Chronic Gastritis **Key Point:** Helicobacter pylori (Type B) gastritis is the most common cause of chronic gastritis worldwide, accounting for ~90% of cases in developing countries including India. ### Types of Chronic Gastritis | Type | Cause | Pathology | Prevalence | | --- | --- | --- | --- | | **Type A (Autoimmune)** | Autoimmune destruction | Fundic gland atrophy, parietal cell loss | 5–10% | | **Type B (H. pylori)** | *Helicobacter pylori* infection | Antral inflammation → intestinal metaplasia | **80–90%** | | **Type C (Chemical)** | Bile reflux, NSAIDs | Foveolar hyperplasia, minimal inflammation | 5–10% | | **Type AB (Mixed)** | H. pylori + autoimmune | Combined features | Rare | **High-Yield:** Although the clinical presentation (parietal cell loss, intestinal metaplasia) superficially resembles Type A autoimmune gastritis, Type B (H. pylori) is far more common globally and in India. The question stem does not explicitly state antiparietal antibodies, which would be diagnostic of Type A. ### Pathogenesis of H. pylori Gastritis 1. **Colonization** — H. pylori adheres to gastric mucosa via flagella and adhesins 2. **Chronic inflammation** — triggers Th1/Th17 response → IL-6, TNF-α, IL-8 3. **Mucosal damage** — neutrophil infiltration → epithelial erosion 4. **Intestinal metaplasia** — chronic injury → replacement of gastric mucosa with intestinal-type epithelium 5. **Atrophy** — progressive loss of glandular cells (including parietal cells) **Clinical Pearl:** H. pylori is a Class I carcinogen (WHO). Chronic infection increases risk of intestinal-type gastric adenocarcinoma and MALT lymphoma. Eradication therapy is recommended even in asymptomatic carriers in high-prevalence regions. ### Distinguishing Type A from Type B Gastritis | Feature | Type A (Autoimmune) | Type B (H. pylori) | | --- | --- | --- | | **Serology** | Anti-parietal, anti-intrinsic factor antibodies | H. pylori IgG/IgM positive | | **Location** | Fundus and body | Antrum > fundus | | **Achlorhydria** | Early and severe | Late (if atrophy develops) | | **Prevalence** | Rare in India | Very common | | **Intestinal metaplasia** | Less common | Common | **Mnemonic:** **HAP** = **H**. pylori, **A**ntrum (primary site), **P**revalent (most common cause of gastritis globally). **Warning:** Do not confuse prevalence with pathology. Both Type A and Type B can cause parietal cell loss and intestinal metaplasia; the distinction lies in etiology and serology. In an Indian patient without explicit mention of autoimmune markers, Type B is statistically most likely.