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What is a capillary malformation?

A capillary malformation — sometimes called a "port-wine stain" — is a kind of birthmark that looks like a flat, red-pink stain on your child's skin.

Capillary malformations are vascular malformations caused by dilated capillaries (small blood vessels) in the skin that enlarge and darken as a child grows older. They are uncommon but not rare; roughly 1 in every 330 babies is born with a capillary malformation.

Capillary malformations usually show up on the face or neck, but can appear anywhere in a child’s body. They are largely cosmetic and often don't require any treatment. Rarely, though, they can be a sign of an underlying abnormality.

Capillary malformations do not fade or go away on their own. However, if a capillary malformation is in a prominent location, specialists can lighten it with pulsed dye laser therapy.

Capillary Malformation | Symptoms & Causes

What are the symptoms of a capillary malformation?

The only sign of a capillary malformation is the birthmark itself: a reddish-pink stain that usually appears on the face or neck, but can show up anywhere in your child’s body. A capillary malformation can darken in color and your child's skin can thicken as she ages, and will grow as your child grows.

Tiny growths called “blebs," which bleed easily and are sometimes painful, can appear from the malformation. A capillary malformation can also be painful if it’s covering a deeper vascular anomaly.

Rarely, a capillary malformation can be a sign of an underlying abnormality. For instance:

  • A capillary malformation over the spinal column can sometimes be associated with spinal abnormalities.
  • A capillary malformation can cover a deeper vascular abnormality involving your child’s arteries, veins or the lymphatic system, such as Klippel-Trenaunay syndrome.
  • Very rarely, if the stain covers part of the forehead and upper eyelid, your baby should be evaluated for neurological problems, as it could be a sign of a very rare condition called Sturge-Weber syndrome. Only 8 percent of kids with a facial capillary malformation have neurological problems.

What causes capillary malformations?

Researchers believe that these malformations occur while your child is still in the womb. For reasons that aren't clear, the capillaries — the smallest blood vessels in the body — expand, allowing a greater-than-normal amount of blood to flow through them, staining the skin.

No known food, medication, or activity a mother did during pregnancy can cause her child to have a capillary malformation.

Capillary Malformation | Diagnosis & Treatments

How is a capillary malformation diagnosed?

A complete medical history and thorough physical exam by a vascular anomalies specialist is usually all that is needed to diagnose a capillary malformation.

If there are any concerns that your child might have an underlying condition, your doctor recommend an imaging study such as a magnetic resonance imaging (MRI). This is a high-resolution scan that allows the doctor to detect any related abnormality in your child’s muscles, nerves, bones, and blood vessels.

You should consult a vascular anomalies specialist if:

  • you are worried that your child may have an underlying condition such as Klippel-Trenaunay syndrome or Sturge-Weber syndrome
  • your child has any pain or bleeding from capillary malformation
  • you want to explore pulsed dye laser therapy as an option for lightening a capillary malformation

What are the treatment options for a capillary malformation?

If your child’s capillary malformation has no underlying complications, it can be left untreated, or it can be lightened using pulsed dye laser therapy.

A pulsed dye laser destroys the abnormal blood capillaries. Pulsed dye laser is the gold standard of treatment for capillary malformations because it’s highly effective, doesn't damage the surrounding skin, and rarely causes scarring.

Every capillary malformation responds differently to laser therapy. Laser therapy usually succeeds in lightening the stain, but doesn't make it go away completely.

In the rare case that a capillary malformation is a sign of an underlying condition, we’ll refer him to the appropriate vascular anomalies specialists to design a treatment plan that addresses the underlying issue as well as the capillary malformation.

You should start treatment when a child is an infant. At this time, the stain is still small and so it’s much easier to treat. Pulsed dye laser therapy will work in older children, though it may require more treatments.

What is the long-term outlook?

Capillary malformations are chronic conditions, but have very few long-term risks. It will grow as your child grows, but rarely do they cause any serious health problems

If your child undergoes pulsed dye laser therapy, your care team will devise a schedule of follow-up care to check on the effectiveness of the laser therapy and decide whether more treatments are necessary.

How we care for capillary malformations

The Vascular Anomalies Center at Boston Children's takes an interdisciplinary approach to care with every child they see, whether the child is initially reviewed at our conference or seen in clinic. While capillary malformations are typically only a cosmetic issue, on your first visit to clinic several VAC specialists will often review your child's case at the same time. Our experience in treating many patients with capillary malformations gives us the depth of knowledge about what symptoms to look for to ensure you have an accurate diagnosis.

Once a diagnosis and the extent of the disease is confirmed, the team works with you to develop and carry out a coordinated care plan that matches your child's specific needs. The team brings the expertise of other Boston Children's departments and services as necessary to provide your child with the best care in a child-friendly atmosphere.

Capillary Malformation | Programs & Services