Which of the following is the most common cause of mitral stenosis in India and other developing countries?

Explanation

## Etiology of Mitral Stenosis: Geographic and Epidemiologic Perspective ### Most Common Cause in Developing Countries **Key Point:** **Rheumatic heart disease (RHD) secondary to acute rheumatic fever (ARF)** is the **most common cause of mitral stenosis worldwide and particularly in India and other developing countries**. ### Epidemiologic Context - **Developed nations**: Degenerative calcification (senile MS) is now the leading cause due to aging populations and effective ARF prevention - **Developing nations**: RHD remains the dominant etiology due to: - High prevalence of group A streptococcal (GAS) infection - Limited access to antibiotics and rheumatic fever prophylaxis - Crowded living conditions facilitating GAS transmission - Malnutrition and poor healthcare infrastructure ### Pathogenesis of Rheumatic Mitral Stenosis 1. **Acute phase**: Pancarditis (endocarditis > myocarditis > pericarditis) 2. **Chronic phase**: Valve fibrosis, commissural fusion, and calcification 3. **Result**: Stenotic, often regurgitant mitral valve (MS ± MR) ### Clinical Features of Rheumatic MS - **Age of presentation**: Typically 20–40 years (younger than degenerative MS) - **Associated findings**: Atrial fibrillation, thromboembolic events, pulmonary hypertension - **Other valve involvement**: Aortic valve disease common; tricuspid and pulmonary valve less common **High-Yield:** In any Indian patient presenting with MS, **assume rheumatic etiology unless proven otherwise**. History of ARF, multiple valve involvement, and young age support this diagnosis. **Mnemonic for RHD sequelae:** **MAST** = **M**itral (most common), **A**ortic, **S**tricuspid, **T**ricuspid (least common). ### Comparison of MS Etiologies | Feature | Rheumatic MS | Degenerative MS | |---------|--------------|------------------| | **Age at onset** | 20–40 years | >60 years | | **Gender** | Female > Male (2:1) | Equal | | **Geography** | Developing countries | Developed countries | | **Associated lesions** | Aortic, tricuspid involvement | Isolated mitral | | **Leaflet appearance** | Thickened, fused commissures, calcified | Calcified annulus, leaflet calcification | | **AF incidence** | High (50–70%) | Lower (20–30%) | | **Prognosis** | Variable; amenable to intervention | Progressive; surgical replacement often needed | **Clinical Pearl:** The presence of **atrial fibrillation in a young patient with MS** is a red flag for rheumatic disease and mandates anticoagulation and consideration for rhythm control or rate control strategies.