Klippel-Trénaunay Syndrome

What is Klippel-Trénaunay syndrome? 

Klippel-Trénaunay Syndrome

Klippel-Trénaunay Syndrome in a child's leg.  

Klippel-Trénaunay syndrome (KTS) is a rare disorder that is present at birth (congenital). Children with KTS have 1 or more of these signs:

The syndrome may cause a wide range of other bone and skin problems. Children with KTS have changes in the PIK3CA gene. KTS is 1 of the conditions on the PIK3CA-related overgrowth spectrum (PROS). 

Klippel-Trénaunay Syndrome at Seattle Children's

Our Vascular Anomalies Program is nationally known for treating children with KTS and other vascular disorders. Vascular refers to the tubes (vessels) that carry blood and lymph in the body. We are 1 of the largest and most experienced programs in the United States.

Doctors from across the nation send children here for treatment because of our specialized expertise. We see nearly 2,000 children with vascular anomalies each year, more than any other hospital in the region.

For more information, contact the Vascular Anomalies Program by email or by calling 206-987-4606. If you would like an appointment, ask your child’s primary care provider to refer you.

Providers, see how to refer a patient

  • The experts you need are here
    • Few hospitals have our experience treating children with KTS. Because it is so rare, doctors with less experience might not manage KTS correctly or may overlook related problems.
    • Our Vascular Anomalies team brings together experts with many different skills and experiences. These include otolaryngologists, orthopedic surgeons, geneticists, interventional radiologists, dermatologists, plastic surgeons, general surgeons, hematologists-oncologists, neurologists, neurosurgeons, ophthalmologists, physical therapists and occupational therapists.
    • Our physician-scientists help set national standards for the care of young people with vascular anomalies. We provide the most advanced treatments in our region.
  • Accurate diagnosis and precision medicine
    • A correct diagnosis is the first step toward improving your child's condition. We have the expertise to accurately diagnose your child. If tests are needed to confirm it, we have a broad range of options, such as genetic testing and imaging studies. These tests help us work with you to decide the best treatment option for your child.
    • Our physician-scientists have created a way to test patients’ tissue and body fluids for the genetic changes known to cause vascular anomaly syndromes. The test is called a gene panel. We can test DNA in tissue sent to us from doctors across the nation. No other children’s hospital has a gene panel certified for clinical use with vascular anomalies. This certification means doctors can make treatment decisions based on the results.
    • This testing may help us identify the abnormal gene causing your child’s condition. A precise diagnosis may expand your child’s treatment options to include drugs that target the biological pathway causing their condition. These drugs may be new targeted therapies or those already used to treat other diseases.
    • Our genetic testing expertise helps us create new therapies that we offer in research studies called clinical trials.
    • Learn more about vascular anomalies research at Seattle Children’s.
  • Making treatment easier on your child
    • Until Seattle Children’s pioneered glue embolization surgery (GES), many children with vascular anomalies endured repeated, painful injections or multiple surgeries. To make it safer and easier to remove a vascular malformation in a single surgery, our team first injects medical-grade Super Glue.


  • Team approach for complete care
    • We schedule visits so your child sees all the specialists they need in as few days as possible. In some cases, we can consult via video phone calls with doctors or patients.
    • Your child’s team will work together – and with you – to make a treatment plan that fits your child’s unique needs. Combining our skills helps make sure your child gets the very best care.
    • As long as is needed, our team keeps a watch on your child’s condition. We are always here to answer your questions and connect you to community resources.
  • We treat your whole child
    • Our specialty is treating children’s disease while helping them grow up to be healthy and productive. 
    • Children do not react to illness, injury, pain and medicine in the same way as adults. They need – and deserve – care designed just for them. Our experts focus on how treatments today affect growing bodies in the future. We provide the best and safest treatment for your child based on our years of experience and the newest research.
    • At Seattle Children's, we work with children and families from around the Northwest and beyond. Whether you live nearby or far away, we can help with financial counseling, schooling, housing, transportation, interpreter services and spiritual care. Read about our services for patients and families.

Symptoms of KTS

Children with KTS often have 1 or more of these signs:

  • A capillary malformation covering 1 or both arms or legs.
  • Swollen or malformed lymphatic vessels or veins (venous malformations).
  • An arm or leg that is larger than the other. These changes in size can also affect the face, head or internal organs.
  • In some children, the bone in 1 part of a limb, such as a toe or finger, may grow unusually large and thick.

Oversized limbs or bones are rarely present at birth. They may start to get much bigger in the first few months or years of life or during puberty.

In some children with a capillary malformation, it gets small, blood-filled, bubble-like growths that can bleed. This tends to happen between puberty and age 30.

Diagnosing KTS

To diagnose KTS, first doctors will:

  • Ask about your child’s health history
  • Examine your child

A team of specialists will work together to diagnose your child, using tests such as:

  • Blood tests
  • Imaging studies
  • Genetic testing

We have created a way to test a patient’s tissue for genetic changes (variants or mutations) known to cause vascular anomalies. Genetic test results help inform your child’s diagnosis and may help guide their treatment.

We also measure your child to see if their arms and legs are the same length on both sides.

After reviewing all the information, the team will recommend a treatment plan for your child.

  • Imaging studies

    The doctor may take pictures of the inside of your child’s body with:

    • MRI (magnetic resonance imaging)
    • Doppler ultrasound
    • Angiogram

    These imaging studies help us:

    • See if there are problems with vessels deep in your child’s body
    • Assess your child’s soft tissue and any overgrowth
    • Look for an abnormal connection between an artery and a vein (arteriovenous fistula)
    • Find what is causing symptoms
    • Confirm the diagnosis of KTS
    • Plan procedures
    • Track changes over time in a vascular malformation or arm or leg
  • Assessing if your child has Parkes-Weber syndrome

    We make sure your child’s symptoms are caused by KTS and not by Parkes-Weber syndrome (PWS). PWS is rarer than KTS. It is more likely to affect an arm, but it can also affect the legs. PWS often causes limbs to get bigger than KTS does.

    Children with PWS have these symptoms that are not found in KTS:

    • Abnormal connections between arteries and veins (arteriovenous fistulas). These can lead to heart failure if not treated.
    • Arteriovenous malformations that can be seen on an angiogram.
    • The affected arm or leg is warmer because the fistulas carry extra blood to that area.

Treating KTS

Treatment for KTS depends on your child’s symptoms. We watch your child closely. If treatment is needed, we review options with your family and come up with the best plan for your child.

It is likely that your child will have a combination of these treatments:

  • Regular check-ups

    We check your child at regular visits. We talk with you about the best way to track KTS and bone changes, such as imaging studies and tests on blood or lymph fluid. Treatment options may change as your child’s condition changes. We partner with you to decide the best care for your child.

  • Compression and lymphedema therapy

    Some children wear a tight-fitting compression stocking, glove or sleeve to prevent fluid from building up in a limb or other part of the body. This fluid buildup is called lymphedema.

    Compression garments do not cure vascular malformations, but can help with pain and mobility. Read more about Compression Garments: Wear and Care (PDF).

    Our certified lymphedema therapists are experienced in working with children to reduce or prevent swelling. They will create a custom treatment plan for your child using complete decongestive therapy (CDT). There are 4 parts to CDT:

    • Skin care
    • Gentle massage to improve flow of lymph
    • Compression therapy
    • Exercise

    Read more.

  • Medicines

    Your child may need pain medicine or antibiotics to prevent or treat infections cause by abnormal blood flow in the area. Some children take medicines such as sirolimus (rapamycin or Rapamune) and aspirin to treat symptoms. 

    Slow blood flow can cause blood clots to form. Blood-thinning medicine can reduce the pain and severity, as well as the number of blood clots.

  • Laser therapy

    You child’s doctor may recommend laser treatment to:

    • Improve the color of the malformation
    • Treat pain
    • Help sores heal

    Laser therapy uses light energy to quickly destroy the extra blood vessels. The type of light beam we use depends on the abnormal vessels.

    Your child may need multiple treatments. Laser treatment often improves skin discoloring, but it does not remove or reduce a mass or bump. 

    We can treat some children in the clinic after using a cream to numb their skin. Your child may need to be treated in the operating room under general anesthesia (your child will be fully asleep). We will talk with you to decide the best choice for your child.

    We offer outpatient laser surgery (done while your child is awake) at our Seattle hospital campus, Bellevue Clinic and Surgery Center and North Clinic in Everett. We do laser treatments that need general anesthesia at our Bellevue center or Seattle hospital campus.

  • Sclerotherapy

    Sclerotherapy (SCLAIR-oh-THAIR-uh-pee) is treatment to block unneeded veins. It can:

    First, a doctor trained in imaging (interventional radiologist) uses ultrasound to find the abnormal veins. Then a doctor injects a solution into the VM to make it shrink over time. Your child’s body will reroute their blood to healthier veins. The affected vessel will form scar tissue. Over time, your child’s body will absorb the scar tissue.

    Some children need this procedure several times to make their VM small enough to reduce pain and prevent problems in the affected area. Sometimes the vessel enlarges again and we need to repeat the procedure. 

    Read more about sclerotherapy (PDF).

  • Surgery on problem vessels

    Sometimes surgery to remove or reduce the size of a venous malformation (VM) or lymphatic malformation (LM) is the best treatment. Options include the following:

    • Clamp off a section of veins to prevent blood flow through a damaged section. This is called vein ligation. It promotes blood flow through healthy veins.
    • Use a metal wire to remove damaged veins. This is called vein stripping.
    • Remove a section of veins from the body (called resection).
    • Block blood flow through a VM and then remove it.
    • Glue embolization surgery (GES) to remove or reduce VMs or LMs. Our doctors were the first to use medical-grade Super Glue to make it safer and easier to remove the tangle of extra vessels in a single surgery.

    At Seattle Children’s, glue embolization surgery is an option for children with malformations in many parts of the body.

  • Treatment for bone and tissue problems

    KTS may cause an arm or leg to grow more skin, muscle or bone than the other limb. This is called overgrowth. It can affect the use of your child’s arm or leg.

    When they are born, most children with KTS have limbs or bones that are typical size. Bigger-than-usual growth may begin within the first few months or years of life or during puberty. We talk with you about the best way to measure and track changes, such as imaging studies.

    If KTS causes problems with your child’s bones, we will work with orthopedic experts to plan the best treatment.

    Your child’s treatment for overgrowth problems may include:

    • Physical therapy or occupational therapy.
    • Surgery to remove the extra tissue or bone. This is called debulking.
    • Wearing shoes with heel inserts if 1 leg is longer than the other. Some children need surgery to correct this.
  • Clinical trials

    For some children, genetic testing helps doctors identify the exact genetic cause of their condition. Such a precise diagnosis may expand treatment options to include drugs that target the biological pathway causing the malformation. If this is the case for your child, our doctors will talk with you about the options and any research studies (clinical trials) that might be a good match.

Contact Us 

If you have questions about a consultation or second opinion, email us or call 206-987-4606. If you would like an appointment, ask your child’s primary care provider to refer you.

Providers, see how to refer a patient

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