Portwine stains (venular or capillary malformations)
Portwine stains are the most common. They occur in about 1 out of every 1,000 people. A portwine stain is an area of skin in which the small veins just under the surface of the skin are dilated. This dilatation will increase the amount of blood in the veins and this will impart a reddish stain to the skin. The underlying cause of the dilatation of these vessels is believed to be an absence of innervation (nerve connection) to the muscle wall surrounding the small veins. Since the embryo develops segmentally (in parts, with each part developing independently), usually only one or two segments may be involved, occasionally, the condition can be more widespread. The absence of nerve connection will result in a muscle wall that has no tone (function) and this in turn will cause these vessels to dilate, hence the increase in blood volume in these vessels and hence the discoloration. Since the blood circulation is dynamic, the intensity of color will vary according to the volume of blood present within the vessels.
Although we group all portwine stains together, there are clearly different types of portwine stain. To date, no sub classification has been proposed. Some prtwine stains are darker than others. This is probably due to the density of affected vessels. Some are confluent whereas others are geographic (broken up) in their distribution.
The intensity of color will vary as the blood flow varies. When the patient is hot or angry, the flow of oxygenated blood will impart a more intense, reddish discoloration to the lesion. The process of aging will affect the portwine stain. A slow steady dilatation of the vessels will result in an increase intensity of color and as th amount of elastin and collagen diminishes, the portwine stain will thicken. Some will form nodules called cobblestones which can get quite large if left untreated. The age of onst of these cobblestones varies from the mid 20’s to the 60’s. It must be stressed that cobblestone formation is not inevitable. In an even smaller percentage of patients, there will be tissue overgrowth or thickening of the soft tissues within the affected area. The exact cause of this is unknown but it appears to be a segmental growth signal abnormality.
Portwine stains may be associated with syndromes, the most important of which is Sturge Weber Syndrome. This condition is an association of a portwine stain, ocular (eye) involvement and involvement of the meninges (the membranes that cover the brain). In its worst form, this syndrome can cause seizures, mental retardation and visual loss. This is NOT inevitable and the reader should be referred to a site that specializes in Sturge Weber Syndrome. Many patients with Sturge Weber Syndrome have very mild disease and live completely normal lives. For more information on Sturge Weber Syndrome click here.
Eye involvement without brain involvement does occur and is more commonly seen if there is skin involvement above and below the eye. This is not Sturge Weber Syndrome. These children should be seen by an ophthalmologist in order to correctly diagnose whether or not there is eye involvement and if so, to treat and prevent complications.