Vascular Malformations

Vascular malformations, or abnormal blood vessel changes, include venous malformations and arteriovenous malformations (AVMs). They may look like birthmarks that develop during infancy. AVMs can form in the brain or spine, causing life-threatening problems. Treatments can close the affected blood vessels.


What are vascular malformations?

Vascular malformations are abnormalities that involve blood vessels. These changes are typically present at birth but frequently may not become evident until later in life during childhood or even in adulthood.

Vascular malformations can develop in any part of your body — from your head to your toes. They may present as a soft tissue mass, pain, swelling and/or skin discoloration. Some vascular malformations develop on your face or neck or near your brain or spinal cord. Others look like birthmarks or red blemishes.

Rarely, vascular malformations develop during adulthood after trauma or another incident. Vascular malformations that cause pain, impair function such as vision or activities or cause bleeding or other problems may need treatment.


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Where do vascular malformations occur?

Vascular refers to blood vessels. Vascular malformations can affect any blood vessel in your circulatory system. They may also develop in lymphatic vessels in the lymphatic system.

Affected blood vessels may include one or more of the following structures:

What are the types of vascular malformations?

Vascular malformations may appear as birthmarks on an infant’s skin. Or they may develop in practically any part of your body, including your brain or spine. Healthcare providers determine the type of vascular malformation based on the affected blood vessels.

The most common types include:

  • Venous malformation: The most common type of vascular malformation, a venous malformation, develops in a vein. Veins carry blood back to your heart to get oxygen.
  • Arteriovenous malformation (AVM): An AVM is a tangle of arteries and veins that connect incorrectly. Instead of connecting to capillaries, the arteries pump blood directly into the veins through a cluster of channels called a nidus. AVMs can affect your brain or spine.
  • Capillary telangiectasia: These small areas of enlarged capillaries tend to develop in the brain. Most capillary telangiectasias don’t cause problems. But occasionally, they cause a hemorrhage.
  • Cavernous malformations: Tightly packed capillaries in your brain have long “caverns” (cavernous malformations). Blood moves slowly through these caverns.
  • Lymphatic malformations: Dilated lymphatic channels forming fluid-containing cysts tend to develop in the soft tissues of your face, neck and axillary (arm pit) regions.


What’s the difference between vascular malformations and hemangiomas?

Vascular malformations and hemangiomas result from irregularities in blood vessels (vascular anomalies). They both can cause birthmark-like blemishes, but there are differences:

  • Hemangiomas are a type of noncancerous (benign) vascular tumor. They form when blood vessels clump together underneath the skin. Strawberry hemangiomas typically appear after birth. They grow rapidly for the first six months of an infant’s life. These tumors rarely cause problems and usually go away without treatment. When hemangiomas are large or affect function or cause pain or other problems, they usually can be managed with a medication that makes them shrink faster. Only very rarely is surgery necessary.
  • Vascular malformations are present at birth but may not be noticeable until childhood or even adulthood. They grow slowly and may extend deeper into nearby tissues and structures, causing problems. Vascular malformations frequently require treatment.

What are slow-flow vascular malformations and fast-flow vascular malformations?

Most vascular malformations are slow-flow. This term means blood moves slowly through the affected blood vessels. These are venous, lymphatic or venolymphatic malformations.

AVMs are fast-flow vascular malformations. Blood moves quickly from arteries to veins, typically through a cluster of abnormal vascular channels called a nidus. This fast blood flow in large AVMs can cause your heart to work harder, increasing the risk of heart failure.


How common are vascular malformations?

Vascular malformations are rare. They occur in about 1% of all births. The most common type, venous malformations, affects approximately 1 in every 5,000 to 10,000 people.

Symptoms and Causes

What causes vascular malformations?

Most vascular malformations are a result of localized or regional abnormal development of vascular and/or lymphatic channels which develop in utero. They are typically present at birth (congenital).

Less commonly, an injury in which there’s unrecognized damage to the vessels can over time develop into a vascular malformation. An injury or hormonal changes during puberty or pregnancy can make venous malformations noticeable for the first time.

In a small number of cases, people inherit genetic changes (mutations) that make vascular malformations more likely. Researchers are still learning more about these genetic causes.

Who is at risk for vascular malformations?

Some people inherit gene changes that cause conditions that increase the risk of vascular malformations. These conditions include:

  • Blue rubber bleb nevus syndrome causes venous malformations in your intestines and digestive system. It also causes dark blue, red or black skin lesions (bumps or patches of skin).
  • CLOVES (congenital lipomatous overgrowth, vascular malformations, epidermal nevi and spine deformities) causes AVMs in your spine. It also causes scoliosis, fatty tissue growths and a deep red rash.
  • Hereditary hemorrhagic telangiectasia (also called Osler-Weber-Rendu syndrome) causes abnormal tangles of small capillaries or AVMs.
  • Klippel-Trenaunay syndrome (KTS) causes port-wine stains, bony or tissue growths and venous or lymphatic malformations.
  • Parkes Weber syndrome causes AVMs in your arms or legs.

What are the symptoms of vascular malformations?

Symptoms of vascular malformations depend on the type. Vascular malformations that affect your skin may look like a raised red, blue, purple, brown or black birthmark. These marks may swell, bleed or cause pain.

An AVM in your brain may not cause symptoms unless it bleeds. AVMs of the brain that bleed can cause headaches, seizures or muscle weakness (paralysis) on one side of your body.

Venous malformations can cause body aches, pain, swelling, problems with blood clotting and organ damage.

Diagnosis and Tests

How are vascular malformations diagnosed?

Because vascular malformations don’t always cause symptoms, providers sometimes discover the condition only after ordering tests to check for a different problem.

Healthcare providers use specialized imaging tests to view blood flow and check for vascular malformations. These imaging tests include:

Management and Treatment

How are vascular malformations treated?

Treatments for vascular malformations focus on minimizing symptoms and reducing potential complications. Malformations that don’t cause problems may not need treatment and can just be observed over time.

Treatments depend on the affected blood vessels. They often involve closing off or surgically removing affected blood vessels. Most malformations can be treated using minimally invasive techniques. Providers may use:

Sometimes, your healthcare provider may recommend a biopsy to confirm the diagnosis and/or to obtain tissue for genetic testing.

Due to the complexity and rarity of vascular malformations, it’s best managed using a team approach with health care providers of multiple specialties.

Can vascular malformations come back after treatment?

Yes, vascular malformations can recur after treatment. You may need regular follow-up and testing to detect a recurrent malformation.


Can you prevent vascular malformations?

Vascular malformations are often present at birth (congenital). That means there isn’t a way to prevent them.

If you have a family history of a condition that causes vascular malformations, you may want to meet with a genetic counselor. This specialist can discuss options to lower the risk of passing the condition to children.

Outlook / Prognosis

What are the complications of vascular malformations?

Some malformations cause no problems and can be observed. More commonly, malformations are likely to cause pain and swelling.

Some malformations interfere with exercise, sports, work or activities of daily living due to pain, or from muscle, joint or nerve involvement.

Large, high flow malformations can over time lead to heart failure.

Vascular malformations in solid organs such as your liver, kidney or uterus can lead to organ dysfunction and other complications.

Certain vascular malformations like AVMs in your brain or spine can reduce the flow of oxygenated blood to your brain. Life-threatening problems may occur, such as:

What is the outlook for people with vascular malformations?

Vascular malformations that appear as birthmarks can affect appearance and self-confidence, leading to depression and anxiety. Most of these malformations respond well to treatments.

More serious malformations like AVMs in your brain can cause life-threatening problems if they begin to bleed.

The vast majority of malformations are treatable and respond well to treatment.

Living With

What should I ask my provider about vascular malformations?

You may want to ask your healthcare provider the following questions:

  • What caused the vascular malformation?
  • What type of vascular malformation do I have?
  • What is the best treatment for me?
  • What are treatment risks or side effects?
  • Should I look out for signs of complications?

A note from Cleveland Clinic

Vascular malformations are a rare blood vessel disorder often present at birth. Less commonly, accidents or hormone changes bring on or worsen these blood vessel changes. Healthcare providers can treat vascular malformations that look like birthmarks, although they may return. AVMs that develop in your brain or spine and cause bleeding can be life-threatening. You should talk to your healthcare provider about preventive steps if you have a genetic condition that increases the risk of vascular malformations.

Medically Reviewed

Last reviewed on 07/06/2022.

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