Port wine stain birthmarks appear as pink, purple, or reddish patches on the skin. They occur due to a malformation of small blood vessels. They are mostly harmless but may result from an underlying health condition.

Another name for this type of birthmark is a congenital capillary vascular malformation.

Port wine stain birthmarks are rare and affect approximately 0.3% of newborns.

This article discusses what a port wine stain birthmark looks like, its causes, complications, and possible treatments. The article also answers some common questions about port wine stain birthmarks.

A port wine stain birthmark on a person's face.Share on Pinterest
Nicola Suttle/Stocksy

Port wine stain birthmarks are pink, purple, or reddish patches of skin.

People most commonly have these birthmarks on their faces. Another common location for port wine stain birthmarks is the neck.

Less commonly, they may appear on a person’s:

  • abdomen
  • arms
  • legs

If a person does not receive treatment for their birthmark, it may get darker as they age. It can also develop nodular thickening over time and may develop small, raised red bumps.

Port wine stain birthmarks can range in size from very small to quite large, according to 2019 research.

If a person’s birthmark does develop vascular nodules, it may be prone to spontaneous bleeding. The birthmark may also bleed internally.

The capillaries are small blood vessels that transport oxygenated blood to the cells in the organs and systems throughout the body, 2022 research explains.

Port wine stain birthmarks occur due to dilated capillaries.

These dilated blood vessels are wider than usual in the affected area, which allows blood to build up in them. This causes an increased number of red blood cells to build up in the skin.

Port wine stain birthmarks may also occur due to a rare vascular disorder called Sturge-Weber syndrome (SWS).

Around 15–20% of children with a facial port wine stain birthmark that involves the ophthalmic nerve are at risk for SWS.

SWS is a condition that can affect the skin, brain, and eyes. According to the National Organization for Rare Disorders, it can cause a person to develop:

SWS may also cause a person to experience seizures and have a weakness on one side of their body. People with SWS may also have developmental delays.

The symptoms and severity of SWS can vary widely from one person to another.

In most cases, port wine stain birthmarks are harmless and do not cause any serious complications.

However, in some cases, they may increase a person’s risk of developing glaucoma. Research from 2015 indicates that up to 10% of people with a port wine stain birthmark may have glaucoma. This is a condition that occurs when pressure rises in the eyes, the National Eye Institute explains.

If a person receives early treatment, they can reduce their risk of serious damage. However, without treatment, glaucoma can damage a person’s optic nerve. This can result in vision loss and sometimes blindness.

Around 3 million people in the United States have glaucoma, and it is the second leading cause of blindness worldwide.

Port wine stain birthmarks often do not require treatment. However, if they do, the most common option is pulsed dye laser treatment.

This treatment aims to destroy the affected capillaries, reducing the amount of blood that is built up in the skin. This may cause the birthmark to fade and become less red.

During this treatment, a medical professional uses lasers to accurately treat a target. In this case, the target is the affected capillaries.

The capillaries absorb the photons, which causes them to heat up. This process ultimately destroys the selected capillaries. This procedure tends to avoid causing damage to the surrounding structures.

Research suggests that healthcare professionals should begin this treatment during a person’s infancy in order to encourage a better outlook.

Below are some of the most common questions and answers about port wine stain birthmarks.

Do port wine stain birthmarks go away?

Port wine stains do not go away on their own. They are permanent birthmarks that fade only after treatment.

Can port wine stain birthmarks become cancerous?

Basal cell carcinoma (BCC) is the most prevalent type of skin cancer, according to a 2020 study. Researchers in the study suggest that there have been around 30 reported cases of people with a port wine stain birthmark developing BCC.

However, the authors state that most of these cases were associated with people who had received radiation therapy to treat their birthmarks much earlier in their life.

This means that radiotherapy treatment for the birthmark may increase a person’s risk of developing BCC. Other things that may increase a person with a port wine stain birthmark’s risk of BCC include high levels of sunlight exposure and advanced age.

More research is necessary to determine whether a port wine stain birthmark increases a person’s chances of developing cancer.

Are port wine stain birthmarks harmful?

Port wine stain birthmarks are often harmless. However, in some cases, they may bleed spontaneously or internally, per 2019 research. In other cases, they may cause a person to develop glaucoma, which can harm a person’s sight, 2015 research suggests.

Port wine stain birthmarks are most common as pink, purple, or reddish patches on the skin of a person’s face. The next most common location for this type of birthmark is the neck. Port wine stain birthmarks may also be present on a person’s abdomen, arms, and legs.

These birthmarks are mostly harmless but may occur due to an underlying health condition.

Port wine stain birthmarks occur due to dilated capillaries. They cause blood to build up in the blood vessels near the skin’s surface, which causes the birthmark to appear.

A person may choose to treat their birthmark with laser therapy. This treatment aims to destroy the affected capillaries. This treatment is most effective when a healthcare professional administers it earlier in a person’s life.