Vascular Malformations

What they are

Vascular malformations are abnormalities in the formation of blood vessels or lymphatic channels. They are present from birth, although some are not noticed until childhood or adolescence. They grow in proportion to the child and do not regress on their own. This distinguishes them from infantile haemangiomas, which are vascular tumours that typically shrink over time. Most arise from somatic (non-inherited) genetic changes in genes such as PIK3CA, TEK and GNAQ. A smaller number are inherited, for example in CM-AVM (RASA1, EPHB4).

Main types

Malformations are grouped by the type of vessel involved and by blood flow (ISSVA classification):

• Slow-flow: capillary (port-wine stains), venous, lymphatic, and combined forms such as Klippel-Trénaunay syndrome.
• Fast-flow: arteriovenous malformations (AVMs) and arteriovenous fistulas, where arteries connect directly to veins.

Venous malformations are the most common type seen by vascular specialists.

Symptoms and signs

• Venous malformations are soft, compressible, bluish swellings that enlarge when the limb is dependent or with exertion. They can cause pain, stiffness and small calcified clots (phleboliths).
• Lymphatic malformations are swellings that can become suddenly enlarged and inflamed after infection or bleeding into the cyst.
• Capillary malformations are flat pink to purple skin stains.
• AVMs are warm, pulsatile lesions that may have a palpable thrill or audible bruit. Over time they can cause pain, bleeding, ulceration, tissue destruction and, rarely, heart strain.
• Limb overgrowth, or a difference in limb length or girth, may occur with combined malformations.

Growth may accelerate during puberty, pregnancy or after trauma.

Diagnosis

• Clinical examination is often highly suggestive.
• Duplex ultrasound is the first-line test, distinguishing slow-flow from fast-flow lesions.
• MRI (with MR venography or angiography where needed) defines the extent and the tissues involved.
• Catheter angiography is reserved for planning treatment of AVMs.
• Blood tests (D-dimer and fibrinogen) screen for localised intravascular coagulopathy in extensive venous malformations.

Treatment

Not every malformation needs treatment. Management is individualised and best delivered by a multidisciplinary team.

• Conservative care: compression garments, elevation, activity modification, and anticoagulant or antiplatelet therapy in selected patients.
• Sclerotherapy: injection of a sclerosant into venous or lymphatic malformations.
• Embolisation: used for AVMs, often before surgery.
• Surgical resection: the option when a lesion is well localised. Complete removal offers the best chance of cure for AVMs, but recurrence can occur after incomplete treatment.
• Endovenous ablation: may be appropriate for abnormal veins such as the lateral marginal vein in Klippel-Trénaunay syndrome, once deep vein patency is confirmed.
• Laser therapy: used for capillary malformations.
• Targeted medical therapy: sirolimus, or alpelisib in selected PIK3CA-related conditions, may be used for extensive or complex lesions in specialist settings.

Risks of treatment

Depending on the modality, risks include swelling, pain, skin injury or ulceration, nerve injury, blood clots, infection and recurrence. Multiple sessions are often required.

When to seek review

Refer for specialist assessment if a lesion is growing, painful, bleeding, ulcerating, causing limb-length or girth difference, or limiting function. Warm, pulsatile lesions and those affecting the head, neck or airway need prompt review.

This page provides general information only and does not replace individual medical advice.