Port-wine stains are caused by an abnormal formation of tiny blood vessels in the skin.

In rare cases, port-wine stains are a sign of Sturge-Weber syndrome or Klippel-Trenaunay-Weber syndrome.

Early-stage port-wine stains are usually flat and pink. As the child gets older, the stain grows with the child and the color may deepen to dark red or purple. Port-wine stains occur most often on the face but can appear anywhere on the body. Over time, the area can become thickened and take on a cobblestone-like appearance.

The health care provider can usually diagnose a port-wine stain by looking at the skin.

In a few cases, a skin biopsy is needed. Depending on the location of the birthmark and other symptoms, the provider may want to do an intraocular pressure test of the eye or x-ray of the skull.

An MRI or CT scan of the brain may also be done.

Many treatments have been tried for port-wine stains, including freezing, surgery, radiation, and tattooing.

Laser therapy is most successful in removing port-wine stains. It is the only method that can destroy the tiny blood vessels in the skin without causing much damage to the skin. The exact type of laser used depends on the person's age, skin type, and particular port-wine stain.

Stains on the face respond better to laser therapy than those on the arms, legs, or middle of the body. Older stains may be more difficult to treat.

Complications may include:

• Deformity and increasing disfigurement
• Emotional and social problems related to their appearance
• Development of glaucoma in people with port-wine stains involving upper and lower eyelids
• Neurologic problems when port-wine stain is associated with a disorder such as Sturge-Weber syndrome

All birthmarks should be evaluated by the provider during a routine examination.