What Are Vascular Malformations

  • Hania Beg MSc Clinical Drug Development, Queen Mary University, London, UK
  • Sindhuja Pandian MDS in Oral Pathology and Microbiology, Annamalai University

Our bodies consist of various complicated mechanisms which help to keep our bodies functioning and in turn, this helps to keep us alive. A part of this complicated mechanism is the vascular structure, which consists of veins, arteries, capillaries, and lymphatic vessels. Veins, arteries, and capillaries transport our blood securely around the body and lymphatic vessels are responsible for maintaining fluid balance and help to supply our bodies with a strong immune system to protect us against microorganisms. 

A vascular malformation is when the blood vessels develop abnormally and this can occur in any part of the vasculature.1 A vascular malformation is a very rare phenomenon and usually, this malformation will have occurred before birth. It usually grows with the infant and does not disappear. However, there are chances that it won't cause any noticeable symptoms until it is triggered by a major or traumatic event such as an accident, injury, pregnancy, or surgery. 

Types of vascular malformations

Capillary malformations

Capillaries are very small blood vessels in the skin. When they become malformed, they may become larger and thus, more visible on the skin. They will be present from birth and they will appear as flat lesions with reddish-pink discolouration of the skin, also known as “port-wine stains”. 2 These malformations can occur anywhere on the body and they can be larger, smaller, singular, or multiple. 

Over time, as the child continues to grow, the lesions will also grow in size and thickness which will cause the lesion to appear darker and often give a thick or lumpy appearance to the affected area. Pyogenic granules, which are inflammatory, raised, and bright red lesions, can also develop around or on the malformation itself and these granules have a tendency to bleed. 

Rarely, capillary malformations can be indicative of an underlying medical condition; any malformation that appears on the spine should be investigated for spinal abnormalities and if they appear on the forehead or upper eyelid, they should be investigated for Strurge-Weber syndrome which involves further abnormalities in the eye and brain. 

Venous malformations (VM)

As the name indicates, VMs are malformations present in the veins.3 The abnormal veins lack smooth muscle in their structure and hence, they enlarge and swell in certain conditions such as pregnancy, puberty, injury, or age. They can be superficial or deep and if they are superficial, they will appear as a blueish discoloration on the skin. VM exist as a singular or multiple malformations. They can vary greatly in size and are commonly seen in areas such as the face, neck, and scalp. 

When the affected area is lower than the rest of the body, or when there is an increase in venous pressure, the abnormal veins fill with blood and cause swelling which can also be painful. Though the blood flow would be slower due to the swelling, VM does not usually impose any strain on the heart. However, poor blood flow poses a risk of the formation of clots, which is a dangerous phenomenon and requires urgent medical intervention. Furthermore, if a clot becomes calcified, it is called a phlebolith.

There are a few complications associated with VM; If they are located on the limbs, they can swell significantly and cause pain; if VM are located on the tongue or around the airway, they can cause problems with speaking and breathing. 

Arteriovenous malformations (AVMs)

AVMs are abnormal and irregular connections or a “snarled tangle of vessels between arteries and veins which can impede blood flow and reduce the supply of oxygenated blood to the surrounding tissue. The affected person is usually born with the AVM but it can also occur shortly after birth. 

AVMs are commonly found in the spinal cord and brain, but they mostly remain asymptomatic (do not cause any symptoms). Some symptoms which can occur are:

  • Headaches
  • Seizures 
  • Nausea and vomiting 
  • Visual disturbances
  • Dizziness and loss of consciousness 
  • Muscle weakness or paralysis 
  • Speech and language problems 
  • Hallucinations and confusion

These symptoms are mostly noticed when people are in their twenties but if no symptoms are noticed till the affected person is in their forties, the AVMs will mostly likely remain undetected. Pregnancy can cause a sudden exacerbation of blood volume which can trigger symptoms of AVMs.

As a further complication, there is a risk for the weakened blood vessel to burst and release blood into the brain (haemorrhage) which can cause brain damage and stroke.4

Lymphatic malformations (LM)

A LM is an abnormally developed lymph vessel and it usually occurs before birth. Often, it remains undetected but if the LM occurs near the skin surface, it can appear as a superficial or deep swelling filled with transparent or blue-purple liquid. 

A LM can be made of macrocysts or microcysts which are large or small pockets respectively, filled with lymph.5 They can vary greatly in size and some LMs can be very large.

LM can be found anywhere on the body, but they are commonly found on the head and neck area. 

Symptoms usually arise if the LM gets large enough to cause obstruction of a nearby tissue or organ. For example, if a large LM is found near the eye, it can cause visual disturbances and displacement of the eyeball. Some complications associated with LM are swelling, bleeding, and infections. 

Causes and risk factors

Since vascular malformations are such a rare phenomenon, the mechanism behind their formation is not fully understood. It is thought that they could mostly be due to genetic mutations (abnormalities) in the local tissue and in extremely rare cases, they could be inherited. 

A few vascular malformations may occur as a part of a larger medical condition. For example, some VM and LM may be associated with Klippel-Trenaunay syndrome and AVMs that occur in the lungs may be linked to an inherited disorder, hereditary hemorrhagic telangiectasia (HHT).


After an initial thorough physical and clinical examination of the abnormality, your doctor may order further imaging diagnostics. Ultrasound (US) is a widely used initial imaging modality and can also provide a basis for further treatment. However, US is largely operator-dependent and might not provide a detailed enough image for larger malformations. 

MRI is also a popular diagnostic tool for malformations and it can provide a more detailed and clearer picture of the malformation. Another advantage of MRIs is that they can also show malformation in relation to nearby organs or tissues. 

CT-angiography can be used if an urgent diagnosis is required but it gives off ionizing radiation which can be harmful. Non-contrast CT can be used to properly visualize any suspected phleboliths or calcifications. 

Sometimes, when a diagnosis is not clear via imaging, a biopsy might be required for more clarity. 


At times, conservative measures might suffice instead of treatment. If the malformation is small, asymptomatic, or causes very little hindrance to daily activities, your doctor might decide to simply leave it alone and keep a close eye on it in case of any changes. Some people might choose other conservative measures such as compression stockings, which can protect the malformation and prevent any swelling during the day.

Percutaneous sclerotherapy is a method that can be used to treat certain malformations. It can be carried out during the day without requiring hospital admission or an overnight stay. A local anaesthetic can be applied on the skin, or a mild sedative can be injected to sedate the patient, especially if there is a child involved. 

This procedure involves injecting an irritant called “sclerosant” into the sacs of the lesions. Sclerosant causes an inflammatory reaction in the sacs, which in turn, causes the walls of the sac to stick to each other and thus, eliminate the malformation. Multiple sessions of this procedure might be required to obtain optimal results. 

At times, percutaneous sclerotherapy might not be effective or if the malformation covers a small, precise area, surgery might be considered. This surgery will be done under general anaesthesia and might leave a small scar. It is also possible that another surgery might be needed later if the malformation recurs. 

Complications and prognosis 

Vascular malformations are benign. They do not spread to other parts of the body, are not inherited, and can generally go undetected if they exhibit no symptoms.

Some complications include swelling and pain if the malformation is located in an area that undergoes constant movement and this pain can sometimes limit daily activity. Puberty and pregnancy can also cause the malformation to enlarge. 

More serious complications such as organ failure can occur if the malformation occurs in an organ. AVMs which occur in the brain and spinal cord can lead to serious conditions such as brain damage and strokes.

However, most vascular malformations respond really well to treatment and do not greatly affect the quality of life. 


Although vascular malformations are rare, future treatment for this condition looks promising. Genetic testing is being introduced for screening patients for drug treatment6 and also for diagnosing unclear lesions. The focus has now been shifted to using approved medications to prevent these malformations from swelling and enlarging and to stop them from recurring after treatment. It is hopeful that medication will be favoured over more traditional treatment methods in the future.

This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Hania Beg

MSc Clinical Drug Development, Queen Mary University, London, UK

Hania is a medical doctor (MBBS), with a MSc in Clinical Drug Development. She has got extensive medical knowledge with prior experience in the Heathcare sector and an in dept understanding of drug development and pharmaceuticals. She is ICH-GCP certified with a special interest in medical writing and research.

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