In chronic rheumatic mitral stenosis, which histological change in the valve leaflet is responsible for the 'fish-mouth' appearance seen on gross examination?

Question

Accepted Answer

B. Commissural fusion due to fibrosis and calcification. ## Chronic Rheumatic Mitral Stenosis: Gross and Microscopic Pathology

### The 'Fish-Mouth' Appearance
**Key Point:** The characteristic **'fish-mouth'** or **'buttonhole'** stenosis results from **commissural fusion**—the two commissures (lateral and medial) of the mitral valve are fused together by fibrosis and calcification, leaving only a narrow central opening that resembles a fish mouth when viewed from above.

### Histological Basis of Commissural Fusion
**High-Yield:** Repeated episodes of acute rheumatic carditis cause:
  1. **Fibrosis** of the valve leaflets and commissural tissue
  2. **Calcification** (dystrophic, not metastatic) within fibrotic tissue
  3. **Collagen deposition** and scarring
  4. **Result:** Commissures become immobile and fused, progressively narrowing the orifice

### Associated Chronic Changes
**Clinical Pearl:** Chronic rheumatic mitral stenosis also features:
  - **Leaflet thickening** due to fibrosis
  - **Chordal shortening** (not elongation) and fusion
  - **Calcification** of leaflets and commissures ("hockey stick" appearance on echocardiography)
  - **Atrial dilation** and fibrillation (due to increased LA pressure)

### Distinction from Other Pathologies
| Feature | Rheumatic MS | Degenerative MS | Congenital MS |
|---------|--------------|-----------------|---------------|
| Commissural fusion | Yes (fibrosis) | No | Rare |
| Leaflet thickening | Yes | Yes (calcific) | No |
| Chordal involvement | Yes (shortening) | No | No |
| Age of onset | Young adult | Elderly | Infancy/childhood |

**Mnemonic:** **FCC** — **F**ibrosis, **C**alcification, **C**ommissural fusion = Fish-mouth stenosis

![Rheumatic Heart Disease diagram](https://mmcphlazjonnzmdysowq.supabase.co/storage/v1/object/public/blog-images/explanation/2934.webp)

Answer

A. Myxoid degeneration of the leaflet substance

Answer

C. Verrucous vegetation deposition along the free edge

Answer

D. Chordal elongation with secondary leaflet prolapse

In chronic rheumatic mitral stenosis, which histological change in the valve leaflet is responsible for the 'fish-mouth' appearance seen on gross examination?

Explanation

Chronic Rheumatic Mitral Stenosis: Gross and Microscopic Pathology

The 'Fish-Mouth' Appearance

Histological Basis of Commissural Fusion

Associated Chronic Changes

Distinction from Other Pathologies

Practice similar questions

Join our NEET PG community

Feature	Rheumatic MS	Degenerative MS	Congenital MS
Commissural fusion	Yes (fibrosis)	No	Rare
Leaflet thickening	Yes	Yes (calcific)	No
Chordal involvement	Yes (shortening)	No	No
Age of onset	Young adult	Elderly	Infancy/childhood