# Vascular Malformations and Kasabach-Merritt Phenomenon

> Vascular malformations and Kasabach-Merritt phenomenon for NEET-PG Dermatology covering haemangioma differences, coagulopathy and sirolimus treatment.

- Canonical URL: https://prepelephant.com/topics/neet-pg/dermatology/vascular-malformations-and-kasabach-merritt
- Exam / course: NEET-PG · Subject: Dermatology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Fitzpatrick's Dermatology; Rook's Textbook of Dermatology; Nelson Textbook of Pediatrics
- How to cite: "Vascular Malformations and Kasabach-Merritt Phenomenon", PrepElephant, https://prepelephant.com/topics/neet-pg/dermatology/vascular-malformations-and-kasabach-merritt

## Direct answer

Vascular malformations are developmental errors of vessel formation that are present from birth, grow with the child and never involute, unlike infantile haemangiomas. Kasabach-Merritt phenomenon is a consumptive coagulopathy with thrombocytopenia and low fibrinogen, classically linked to kaposiform haemangioendothelioma or tufted angioma. Sirolimus is a widely used systemic treatment for complicated lesions, while embolisation or surgery suits localised malformations.

## What you must remember

- **Malformation endothelium:** vascular malformations are GLUT-1 negative, whereas infantile haemangiomas express GLUT-1 and undergo proliferation and involution.
- **Slow-flow lesions:** capillary (port-wine stain), venous and lymphatic malformations cause swelling, discolouration and a soft, compressible or cystic feel.
- **High-flow lesions:** arteriovenous malformations are warm, pulsatile and may show a bruit or thrill, and large ones can cause high-output heart failure.
- **Kasabach-Merritt phenomenon:** consumptive coagulopathy with thrombocytopenia, low fibrinogen, raised D-dimer and microangiopathic haemolytic anaemia.
- **Causative tumours:** kaposiform haemangioendothelioma and tufted angioma, not infantile haemangioma, are the usual causes.
- **Diagnostic clue:** a rapidly enlarging, firm, painful lesion in an infant or child, often on the trunk or limbs, raises concern for Kasabach-Merritt.
- **Treatment:** sirolimus is widely used for complicated lesions; vincristine and interferon are older options, and compression helps venous malformations.

## Sorting a vascular lesion and checking the blood

A vascular lesion that enlarges quickly or causes bruising needs assessment for coagulopathy. The steps below move from classification to the blood count and treatment choice.

1. **Classify the flow:** a warm, pulsatile lesion with a bruit suggests a high-flow arteriovenous malformation, whereas a soft or compressible lesion suggests a slow-flow type.
2. **Stain the endothelium:** GLUT-1 positivity favours infantile haemangioma, while its absence supports a malformation or kaposiform haemangioendothelioma.
3. **Note the behaviour:** a rapidly enlarging, painful, firm lesion in a young child raises concern for a kaposiform tumour.
4. **Check the blood:** platelet count, fibrinogen, D-dimer and a blood film for schistocytes detect consumptive coagulopathy early.
5. **Manage bleeding carefully:** transfusion strategy is individualised with haematology input, because platelets and factors can be consumed within the tumour.
6. **Start systemic therapy:** sirolimus is widely used for complicated malformations and kaposiform lesions, with vincristine and interferon as older options.
7. **Plan local treatment:** embolisation, sclerotherapy or surgery suit localised lesions, and compression is used for venous malformations.

## Where the exam tries to catch you

Vascular lesions in infancy are often named wrongly, and Kasabach-Merritt is easily reduced to a platelet problem.

- **Trap:** labelling every vascular lesion in infancy as haemangioma. **Correct:** a lesion present from birth that grows proportionately is a malformation and will not involute.
- **Trap:** expecting propranolol to control a rapidly growing kaposiform lesion. **Correct:** kaposiform haemangioendothelioma is GLUT-1 negative and responds poorly to propranolol, so sirolimus is commonly used.
- **Trap:** treating Kasabach-Merritt as a simple platelet deficiency. **Correct:** it is a consumptive coagulopathy, so fibrinogen, D-dimer and the blood film must be checked alongside platelets.
- **Trap:** planning complete excision of a large infiltrative malformation in one operation. **Correct:** such lesions often infiltrate tissue, so staged treatment or embolisation is commonly preferred.

## Frequently asked questions

### What distinguishes a vascular malformation from infantile haemangioma?

Vascular malformations are present from birth, grow proportionately with the child and do not involute. Infantile haemangiomas appear in early infancy, proliferate and then regress, and they express GLUT-1 while malformations do not.

### Which tumours cause Kasabach-Merritt phenomenon?

Kasabach-Merritt phenomenon is classically associated with kaposiform haemangioendothelioma and tufted angioma. These tumours trap platelets and consume clotting factors, which is why infantile haemangioma does not usually cause this complication.

### What laboratory findings suggest Kasabach-Merritt phenomenon?

Thrombocytopenia, low fibrinogen, raised D-dimer and microangiopathic haemolytic anaemia with schistocytes on the blood film suggest Kasabach-Merritt phenomenon. These findings reflect consumptive coagulopathy within a rapidly growing vascular tumour.

### Which drug is commonly used for complicated kaposiform haemangioendothelioma?

Sirolimus is commonly used for complicated kaposiform haemangioendothelioma and Kasabach-Merritt phenomenon, often alongside other supportive measures. Propranolol is generally less effective for these tumours than for infantile haemangioma.

### When are embolisation or surgery used for vascular malformations?

Embolisation, sclerotherapy or surgery are used for localised vascular malformations that are accessible or cause symptoms such as bleeding or pain. Extensive or infiltrative malformations usually need a staged, multidisciplinary plan rather than a single operation.