Klippel-Trenaunay Syndrome

Klippel-Trenaunay syndrome is a rare congenital blood vessel disorder. It forms before birth and is usually visible at birth or in the first years of life. Usually only one leg is affected, but the disorder can also involve the pelvis, abdomen, chest, or arm. Both males and females can have it.

Three Main Features

The first feature is a pink to purplish birthmark on the skin, called a capillary malformation or port-wine stain. The second feature is vein abnormalities, including varicose veins from a young age, an unusual large vein on the outer side of the leg (lateral marginal vein), and sometimes underdeveloped deep veins. The third feature is overgrowth of soft tissue or bone, so the affected leg is larger or longer. Some people also have lymphatic vessel abnormalities that cause swelling or small fluid-filled blisters on the skin.

What Causes It

Most cases are linked to a change in the PIK3CA gene that occurs after conception and is present in only some of the body's cells. For this reason, the syndrome is generally not inherited from parents and rarely recurs in siblings or children. Experts place it within the group of PIK3CA-related overgrowth disorders (PROS).

Course of the Disease

The disorder is lifelong, and its severity varies greatly from one person to another. Some people have only a birthmark and a slight difference in leg size. Others experience pain, swelling, and skin changes like those in chronic venous insufficiency, covered on the Chronic Venous Insufficiency page. Blood that flows slowly in widened veins makes clots form more easily, including in the deep veins, covered on the Deep Vein Thrombosis page.

Treatment is tailored to the symptoms and carried out together by several specialists, for example a vascular specialist, dermatologist, orthopedic specialist, pediatrician, and physical medicine and rehabilitation specialist. Compression is the foundation of care, while procedures and medications are chosen for more severe symptoms. With regular checkups, many people with this syndrome can go to school, work, and carry on with daily activities as usual.

The diagnosis is usually made from a physical examination by a doctor familiar with blood vessel disorders: the birthmark on the skin, vein abnormalities, and the difference in leg size. The doctor also distinguishes it from similar disorders, for example Parkes Weber syndrome, which has direct connections between arteries and veins.

Duplex ultrasound is used to map the superficial and deep veins, including checking whether the deep veins have developed normally. This is important before any procedure on varicose veins, because the superficial veins are sometimes the main route for blood returning to the heart. MRI with contrast or MR venography shows the extent of blood vessel and lymphatic abnormalities, including into the pelvis and abdomen.

X-rays of the legs measure differences in bone length. Blood tests such as D-dimer and fibrinogen help assess clotting within the vein abnormalities. Testing for the PIK3CA gene in a sample of affected tissue may be considered, especially if the diagnosis is unclear or targeted drug therapy is planned.

Take your baby or child to a doctor if you notice a large reddish purple birthmark along with a larger leg or varicose veins from an early age. People already diagnosed need regular checkups. Go to the emergency room right away if a leg suddenly becomes swollen and painful, you develop shortness of breath, or bleeding is hard to stop.

• A large birthmark along with a difference in the size of the legs or arms
• A child who limps or has different left and right shoe sizes
• Leg pain or swelling that occurs more often
• A hard, red, painful vein lump
• Blood in the urine or stool
• Plans for pregnancy, surgery, or using birth control pills