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What is Klippel-Trenaunay syndrome?

Klippel-Trenaunay syndrome (KTS) is a rare congenital (present at birth) vascular anomaly that results in your child having a large number of abnormal blood vessels. Doctors can sometimes see evidence of KTS in a prenatal ultrasound, and the capillary malformation (in the form of a "port-wine stain" birthmark) is almost always apparent at the baby’s birth. KTS is equally common in boys and girls.

How we care for Klippel-Trenaunay syndrome

The Vascular Anomalies Center (VAC) at Boston Children's specializes in innovative, family-centered care for children with KTS. From your first visit, you’ll work with a team of professionals who are committed to supporting all your family’s physical and psychosocial needs. KTS is a progressive condition, which means that it will grow as your child grows. That said, many kids — especially those with mild cases of KTS — go on to live normal, healthy lives. Treatment for your child’s symptoms is the most effective way to manage the disease.

Children with KTS sometimes have legs so large that it becomes debilitating, forcing them to use a wheelchair. Surgeons at Boston Children's are leading the charge in removing the extra tissue that grows as a result of KTS. In what's called a debulking procedure, our surgeons remove a great deal of the extra tissue, which can allow your child to regain leg function.

Our areas of innovation for Klippel-Trenaunay syndrome

KTS is caused by errors that occur when blood and lymphatic vessels are forming. The Vascular Anomalies Center conducts research that may lead to the development of new, more effective treatments and perhaps ultimately result in ways to prevent KTS.

Our investigators are currently probing the genes and molecules that regulate the formation and growth of blood and lymphatic vessels. We hope that understanding the genes that control these molecular events will result in new therapies for vascular malformations.

Klippel-Trenaunay Syndrome | Symptoms & Causes

What are the symptoms of Klippel-Trenaunay syndrome?

KTS often has three characteristic signs:

  • capillary malformation covering one or more limbs (arm or leg)
  • hypertrophy — or excessive growth — of a limb (usually a leg)
  • abnormal blood vessels, including veins, capillaries and lymphatic vessels
  • (vessels that drain fluid that leaks from arteries and veins and return that fluid to the bloodstream)

KTS affects different kids in different ways. One child may have a mild form of the syndrome with a small capillary malformation and one hand or foot slightly larger than the other. Another child may have a capillary malformation that runs from their chest down their leg, lots of swelling and one limb that is much larger than the other. Symptoms of KTS include:

  • blood clots
  • cellulitis (infections in the skin) — your child may be more prone to infection because they are more likely to bleed easily as a result of the abnormal capillaries near the surface of their skin
  • anemia due to blood loss from easy bleeding
  • pain and heaviness of the affected limb, often severe
  • difference in size between the affected and non-affected limb
  • lymphatic abnormalities such as cysts and swelling
  • swollen veins

What causes Klippel-Trenaunay syndrome?

No one knows the precise cause of KTS. Some doctors think it's caused by a mutation that occurs before birth (but isn’t inherited) in the cells that form the lymphatic system, veins and other tissues. No known food, medication or activity during pregnancy can cause KTS.

Klippel-Trenaunay Syndrome | Diagnosis & Treatments

How is Klippel-Trenaunay syndrome diagnosed?

Doctors can sometimes see evidence of KTS in a prenatal ultrasound, and the capillary malformation (port-wine stain) is almost always apparent when your child is born.

If your child is older and you believe they have KTS, doctors in our Vascular Anomalies Center will start with a complete medical history and a thorough physical exam. In many cases, that initial exam gives us enough information to diagnose KTS.

If there’s any doubt, your doctor may recommend one or more of the following imaging tests, which can help determine the correct diagnosis and the appropriate next steps in treatment:

What are the treatment options for Klippel-Trenaunay syndrome?

There is no cure for Klippel-Trenaunay syndrome (KTS). Treatment aims to improve your child’s mobility, prevent infections or complications and manage pain and other symptoms. Treatment for KTS depends on its symptoms and severity. Some children with mild KTS may need a few treatments, while others with more complex cases may undergo several treatments and ongoing care.


Immunosuppressant medications have proven effective for slowing the growth of vascular anomalies and shrinking tumors. We use sirolimus, also known as rapamycin, which suppresses the immune system and targets lymphatic vessel formation.

Supportive care

Your child’s doctor may recommend various pain medications and antibiotics to help manage symptoms. Other options include:

  • Compression garments: Tight-fitting pieces of clothing worn on the affected limb can reduce pain and swelling. They can also help protect your child’s limb from bumps and scrapes. 
  • Heel inserts: These inserts help children walk normally if their legs are slightly different lengths. 
  • Anticoagulant therapy: Blood clots can form in the abnormal blood vessels of children with KTS and travel to the heart or lungs. Blood-thinning medications help prevent these clots from forming.


A number of surgical options can treat complications from KTS. These include:

  • Debulking surgery: Some children need debulking surgery to remove abnormal vessels and overgrown tissue. This procedure can help reduce the size of your child’s affected limb and improve function. Though debulking is a major, invasive operation, it can be life-changing for children who have limited mobility due to limb abnormalities or painfully overgrown veins.
  • Orthopedic surgery: KTS can cause your child’s foot or leg to become excessively large. Orthopedic procedures include those that reshape the foot to better fit into a shoe, as well as epiphysiodesis, a procedure that stops the leg from growing once a child reaches his or her early teens.

Minimally invasive treatments

An interventional radiologist is a board-certified specialist who performs minimally invasive, targeted treatments throughout the body that do not require open surgery. For KTS, these include:

Klippel-Trenaunay Syndrome | Programs & Services