Which of the following is the most common cause of acute rheumatic fever (ARF)-induced mitral stenosis in India?

Explanation

## Pathogenesis of ARF-Induced Mitral Stenosis **Key Point:** Acute rheumatic fever (ARF) is the leading cause of acquired mitral stenosis globally, and in India it remains endemic due to high GAS prevalence and delayed antibiotic access. ### Mechanism of GAS-Induced Valve Damage 1. **Initial infection**: Group A Streptococcus pharyngitis (not skin infection) 2. **Molecular mimicry**: GAS M protein shares epitopes with cardiac myosin, tropomyosin, and valve proteins 3. **Autoimmune response**: Cross-reactive antibodies and T cells target valve endothelium 4. **Valve pathology**: Verrucous vegetations along closure line → fibrosis and calcification → stenosis **High-Yield:** The latency between GAS pharyngitis and ARF is 2–3 weeks; only 3% of untreated GAS pharyngitis progresses to ARF, but recurrent infections dramatically increase risk. ### Why Mitral Valve? - Highest pressure gradient across valve → greatest mechanical stress on inflamed endocardium - Mitral > aortic > tricuspid > pulmonary (in order of frequency) - Pure mitral stenosis is pathognomonic for ARF (unlike aortic stenosis, which is often degenerative) **Clinical Pearl:** In endemic areas like India, a young patient with mitral stenosis and a history of "joint pain" or "rheumatic fever" should be presumed ARF-related until proven otherwise. **Mnemonic: GASP** — Group A Strep Pharyngitis → Autoimmune response → Stenosis/Regurgitation → Permanent valve damage