Klippel-Trenaunay (klih-PEL tray-no-NAY) syndrome is a rare disorder found at birth (congenital) involving abnormal development of blood vessels, soft tissues, bones and the lymphatic system. Rarely, fusion of fingers or toes, or having extra fingers or toes, also occurs at birth.

People who have Klippel-Trenaunay syndrome may have the following features, which can range from mild to more extensive:

  • Port-wine stain. This pink to reddish-purple birthmark is caused by swelling of tiny blood vessels (capillaries) under the skin. The birthmark usually covers part of one leg, and sometimes one arm, and may get darker or lighter with age. Some areas may be prone to bleeding and infections.
  • Vein malformations. These include swollen, twisted veins (varicose veins) usually on the surface of the legs, which can cause major pain and skin ulcers due to poor circulation. Deeper abnormal veins in the arms, legs, abdomen and pelvis can increase the risk of blood clots (deep vein thrombosis) and cause a life-threatening condition called pulmonary embolism if they dislodge and travel to the lungs. Spongy tissue filled with small veins in or under the skin can cause bleeding, infection or inflammation.
  • Overgrowth of bones and soft tissue. This begins in infancy and is usually limited to one leg, but it can occur in an arm or, rarely, in the trunk. This overgrowth of bone and tissue creates a larger and longer extremity. The overgrowth can cause pain, a feeling of heaviness and problems with movement.
  • Lymphatic system abnormalities. The lymphatic system is part of your immune system, which protects you against infection and disease. An abnormality can cause fluid buildup and swelling in the tissues of your arms or legs (lymphedema), the development of small masses (lymphatic cysts) in the spleen, or infection of the layer under the skin (cellulitis).

The cause of Klippel-Trenaunay syndrome is unknown, but may involve genetic changes that are not inherited (mutations). But more research is needed to determine the causes.

Sept. 17, 2015