A capillary malformation (commonly referred to as a portwine stain), is a flat, sharply defined vascular stain of the skin. It may cover a large surface area or it may be scattered and appear as little islands of color. It can be anywhere on the body and in more than one place on the body (illustration 1), but is most commonly seen in the head/neck region (illustration 2). The exact cause of this lesion is not known, but it is thought that it arises because of abnormal formation of the tiny blood vessels of the skin early in the life of the embryo, after the larger blood vessels are in place. Capillary malformations are unrelated to drugs or medications that may have been taken during pregnancy or to environmental exposures that may have occurred at that time.
Although the number of blood vessels in a capillary malformation is normal, the diameter of the affected vessels is much larger than that in normal vessels; this enlargement results in increased blood flow. Because the vessels are close to the surface, this increased flow gives the skin its pink to purple appearance. As your child grows, the affected blood vessels will continue to enlarge and thicken, causing the color of the lesion to darken. Over time, the clusters of tiny, dilated venules (small vessels that collect blood from the capillary junctions and join to form veins) give a lumpy appearance to the skin. The period of time over which this progression occurs varies greatly from person to person, and may even be delayed until ages 40, 50, or 60.
Capillary malformations on the forehead and upper eyelid can be associated with lesions of the brain and eye (Sturge-Weber syndrome).
Capillary malformations in the skin over the spine can be associated with Cobb syndrome, which involves the spine and/or meninges (tissue covering the spinal cord). Capillary malformations in this area can also be associated with other abnormalities of the spine, and should be investigated with an ultrasound prior to 6 months of age, or an MRI after.
Capillary malformations also can overlie other vascular lesions such as lymphatic malformations, venous malformations, or arteriovenous malformations.
Some commonly seen birthmarks in fair-skinned infants are capillary malformations. When these birthmarks appear on the forehead, eyelids, nose, or upper lip, they are often referred to as "angel kisses." When located on the base of the neck, they are often referred to as "stork bites." These lesions usually fade by 1 year of age and do not require treatment.
Complications of Capillary Malformation
A capillary malformation can also be associated with overgrowth or undergrowth of underlying soft tissues or bones. Also, the color of a facial lesion can darken and the skin can thicken with age. If the lesion occurs on the face and involves the eyelids, other problems such as glaucoma or seizures may occur (Sturge-Weber syndrome).