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# Mitral valve prolapse: myxomatous degeneration and what it leads to

- Lesion

In mitral valve prolapse, the valve leaflets become soft and floppy and bulge back into the atrium when the heart contracts.

Updated Nov 12, 2026

## Key points

- Auscultation: mid-systolic click, sometimes followed by a late systolic murmur.
- Gross: hooded, ballooning leaflets; elongated, thinned or ruptured chordae; the annulus may dilate.
- Micro: expanded spongiosa with mucoid (myxomatous) material; attenuated fibrosa and collagen.
- Associations: Marfan syndrome (fibrillin-1, excess TGF-β), Ehlers–Danlos and other connective tissue disorders.
- Complications (minority): severe mitral regurgitation, infective endocarditis, arrhythmia, emboli from thrombi on the leaflets, rarely sudden death.

## What it is

In mitral valve prolapse, one or both mitral leaflets are enlarged, redundant and floppy and balloon back into the left atrium during systole. It affects about 2 to 3 % of adults. The basic change is myxomatous degeneration: the middle spongiosa layer thickens with proteoglycan and the fibrosa layer, which gives strength, thins. Most cases are isolated and probably genetic; some occur with Marfan syndrome and other connective tissue disorders. Most people have no symptoms, but some develop regurgitation, endocarditis, arrhythmias or chordal rupture.

## Structure

- Gross: intercordal ballooning (hooding) of the posterior leaflet is most typical; leaflets thick and rubbery.
- Microscopy: proteoglycan-rich spongiosa intruding into the fibrosa; secondary fibrosis on the leaflet surfaces where they rub.
- Similar myxomatous change can affect the tricuspid, aortic or pulmonary valves.

## Clinical notes

- Most people with prolapse have a normal life expectancy; severe regurgitation may need valve repair.

## Memory aid

A floppy sail full of jelly: it clicks when it billows back, and leaks when its ropes snap.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the key histological change in mitral valve prolapse?

Myxomatous degeneration: thickening of the spongiosa with proteoglycan and thinning of the collagen-rich fibrosa.

## Which auscultatory finding is classic?

A mid-systolic click, often followed by a late systolic regurgitant murmur.

## Which genetic syndrome is commonly associated with mitral valve prolapse?

Marfan syndrome (fibrillin-1 mutation).

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## Elsewhere in DurgiPedia

- [Fibrillin-1](https://durgical.com/en/biochemistry/enzymes/fibrillin-1/)
- [Heart sounds: S1, S2 and its splitting, S3 and S4](https://durgical.com/en/clinical-exam/heart-sounds-s1-s2-and-its-splitting-s3-and-s4/)

## Connections

## Related 3

- [Valve disease: causes by valve](https://durgical.com/en/general-pathology/valve-disease-causes-by-valve/)
- [Infective endocarditis](https://durgical.com/en/general-pathology/infective-endocarditis/)
- [Aneurysms: types and pathogenesis](https://durgical.com/en/general-pathology/aneurysms-types-and-pathogenesis/)

## Related conditions 5

- [Mitral valve prolapse](https://durgical.com/en/conditions/mitral-valve-prolapse/)
- [Mitral regurgitation](https://durgical.com/en/conditions/mitral-regurgitation/)
- [Marfan syndrome](https://durgical.com/en/conditions/marfan-syndrome/)
- [Infective endocarditis](https://durgical.com/en/conditions/infective-endocarditis/)
- [Atrial fibrillation](https://durgical.com/en/conditions/atrial-fibrillation/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Mitral valve prolapse: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000180.htm) (MedlinePlus, US National Library of Medicine, 2025); [Mitral Regurgitation](https://www.ncbi.nlm.nih.gov/books/NBK553135/) (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/mitral-valve-prolapse-myxomatous-degeneration-and-what-it-leads-to/