A port-wine stain is a birthmark that causes a reddish-purple patch of skin. The birthmark is composed of enlarged capillaries, which give it the distinctive color.
Port-wine stains usually occur at birth and are typically initially flat, and may become darker and raised as the child ages. The birthmarks are typically found on the head and neck, but may occur anywhere on the body.
Acquired port wine stains may occur at an older age and may be caused by a traumatic injury. This is extremely rare.
Port-wine stains may cause emotional and social problems due to their cosmetic appearance.
Port-wine stains may be a single finding or be associated with visual, nervous system, or skeletal abnormalities.