• Disease Overview
  • Synonyms
  • Signs & Symptoms
  • Causes
  • Affected Populations
  • Disorders with Similar Symptoms
  • Diagnosis
  • Standard Therapies
  • Clinical Trials and Studies
  • References
  • Programs & Resources
  • Complete Report

Klippel-Trenaunay Syndrome


Last updated: 6/6/2023
Years published: 1987, 1990, 1998, 2000, 2002, 2008, 2012, 2015, 2018, 2023


NORD gratefully acknowledges John B. Mulliken, MD, Co-Director, Vascular Anomalies Center, Director, Craniofacial Center, Boston Children’s Hospital, for assistance in the preparation of this report.

Disease Overview


Klippel-Trenaunay syndrome (KTS) is a rare vascular disorder that is present at birth (congenital) and characterized by three features: cutaneous capillary malformation (“port-wine stain”), lymphatic anomalies and abnormal veins in association with variable overgrowth of soft tissue and bone. KTS occurs most frequently in the lower limb and less commonly in the upper extremity.


The eponym KTS generated controversy in the medical literature since the first report of the condition in the early 20th century. The French physicians, Klippel and Trenaunay, described patients with capillary stains (improperly called “hemangiomas” at that time), venous varicosities and overgrowth. In the same era, the English dermatologist, Parkes Weber, reported the combination of “hemangiomas” and overgrowth of a limb. For many years, the names of all three physicians were linked as a confusing (and incorrect) term “Klippel-Weber-Trenaunay syndrome,” which unfortunately is sometimes used to this day.

Since the latter 20th century, it is well-recognized that Parkes Weber and Klippel-Trenaunay syndromes are entirely different. Parkes Weber syndrome consists of fast-flow, multiple microscopic arteriovenous connections with variable capillary staining of an enlarged limb (usually the lower extremity). In contrast, KTS is a slow flow combined vascular disorder involving abnormal capillaries (C), lymphatics (L) and veins (V). Therefore, many investigators use the abbreviation CLVM, rather than KTS, and restrict the designation for patients who have all three anomalous vascular components. Other authors apply the KTS term more broadly and include patients with only capillary stain (CM) or combined capillary and venous anomalies (CVM) in the lower limb in the absence of lymphatic abnormalities. Now that genetic testing is available, it is possible to more precisely diagnose patients with these various combinations of vascular anomalies.

  • Next section >
  • < Previous section
  • Next section >


  • KTS
  • < Previous section
  • Next section >
  • < Previous section
  • Next section >

Signs & Symptoms

Capillary Malformation (CM)
At birth, KTS presents with scattered, geographic capillary stains. With age, the surface of the CM becomes studded with tiny lymphatic vesicles that often ooze clear fluid and turn black due to intralesional bleeding.

Lymphatic Malformation (LM)
LM presents as localized or generalized overgrowth caused by micro- and macrocystic anomalies, sometimes in association with lymphedema. Often there is lymphatic swelling and fatty deposition on the opposite foot. The lymphatic anomalies can also occur in the pelvis, bladder and lower gastrointestinal tract. Lymphatic cysts in the spleen are also common. LM is documented by ultrasonography and/or MRI. Lymphography shows that lymphedema is the result of diminished number or absence of lymphatic channels.
Episodic infections (cellulitis) are common and probably related to poor lymphatic drainage in the limb.

Venous Malformation (VM)
Venous abnormalities are always present but variable and involve the entire affected extremity. Typically, there are anomalous embryonic veins called the “marginal system.” Dilatation of superficial veins may not be apparent in infancy but becomes more prominent with age. LM and VM can also involve the pelvic or abdominal organs resulting in bleeding from the rectum, vagina or urinary bladder. Abnormal fatty deposits accompany the venous and lymphatic anomalies.

Many patients with extensive abnormal veins have a low-grade hematologic condition called “localized intravascular coagulopathy” (LIC), this can be determined by measuring increased D-dimers in the blood. Stagnant blood in the dilated veins may clot and trigger a generalized bleeding disorder called “disseminated intravascular coagulopathy” (DIC).

Enlargement of the limb can be minimal to extremely distorted. Overgrowth in length often occurs; however, in some patients the affected limb is shorter than normal. Frequently there is enlargement of the opposite foot.

  • < Previous section
  • Next section >
  • < Previous section
  • Next section >


KTS is caused by a change (variant or mutation) in the PIK3CA gene. This mutation does not occur in the germ cells (egg and sperm) but only in the body cells after fertilization. Therefore, KTS is not an inherited condition and is not passed on in a family.

  • < Previous section
  • Next section >
  • < Previous section
  • Next section >

Affected populations

Klippel-Trenaunay syndrome is a rare disorder affecting males and females in equal numbers. The disorder occurs worldwide.

  • < Previous section
  • Next section >
  • < Previous section
  • Next section >


KTS is diagnosed based on physical signs and symptoms. Computed axial tomography (CAT) and magnetic resonance imaging (MRI) scans, and color doppler studies may be useful in determining the extent of the condition and how best to manage it.

  • < Previous section
  • Next section >
  • < Previous section
  • Next section >

Standard Therapies


Recommended management for the following malformations associated with KTS:

Capillary Malformation
The vesicles in the CM can be improved by laser therapy, sclerotherapy or sometimes
resection and closure of the skin or replacement with a split-thickness skin graft.
Lymphatic Malformation
Macrocystic LM can be deflated by sclerotherapy (injection of irritating solutions). Microcystic LM is less responsive to sclerotherapy and may require resection.

Venous Malformation
Blood stagnates in large, dilated veins, and thus there is a risk for initiating a clotting disorder or thrombosis and pulmonary embolism. Anticoagulation with heparin (subcutaneously injected) is often necessary prior to radiologic or surgical intervention. Conversion to a direct oral anticoagulant (DOAC) may be considered. Large venous channels can be obliterated by sclerotherapy or endovascular laser. Chronic bleeding from the colon may require surgical resection. Bleeding lesions in the bladder can be controlled by laser through a cystoscope. An elastic compressive stocking is useful to minimize discomfort and swelling due to venous distension in the limb.

Enlarged toes may require amputation to narrow the foot and permit footwear. Discrepancy in leg length can be corrected by inserting a lift in the shoe on the normal foot to prevent compensatory curvature of the spine (scoliosis). Surgical closure of the growth plate at the knee (epiphysiodesis) is often needed to equalize leg length.
Staged contour resection is possible to diminish girth of the limb. These procedures are less effective if the abnormal fat and vasculature extends beneath the deep fascia of the leg into the muscle layer.

  • < Previous section
  • Next section >
  • < Previous section
  • Next section >

Clinical Trials and Studies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]

Some current clinical trials also are posted on the following page on the NORD website:

For information about clinical trials sponsored by private sources, contact:

For information about clinical trials conducted in Europe, contact:

Contact for additional information about Klippel-Trenaunay syndrome:

Vascular Anomalies Center (VAC)
Boston Children’s Hospital
300 Longwood Avenue
Boston, MA 02115
Tel: 617-355-5226
Email: [email protected]
Website: http://www.childrenshospital.org/vac

Clinical Practice Guidelines for Klippel-Trenaunay Syndrome (KTS)

https://k-t.org/assets/images/content/BCH-Klippel-Trenaunay-Syndrome-Management-Guidelines-1-6-2016.pdf Updated 1/6/2016. Accessed April 27, 2023.

  • < Previous section
  • Next section >
  • < Previous section
  • Next section >


Mulliken JB, Burrows PE, Fishman SJ (eds). Mulliken and Young’s Vascular Anomalies: Hemangiomas and Malformations. 2nd edition. New York: Oxford University Press. 2013.

Luks VL, Kamitaki N, Vivero MP, et al. Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA. J Pediatr. 2015 Apr;166(4):1048-54.e1-5. doi: 10.1016/j.jpeds.2014.12.069. Epub 2015 Feb 11. https://www.ncbi.nlm.nih.gov/pubmed/25681199

Klippel-Trenaunay syndrome. MedlinePlus. May 17, 2021. Klippel-Trenaunay syndrome: MedlinePlus Genetics. Accessed April 27, 2023

  • < Previous section
  • Next section >

Programs & Resources

RareCare® Assistance Programs

NORD strives to open new assistance programs as funding allows. If we don’t have a program for you now, please continue to check back with us.

Additional Assistance Programs

MedicAlert Assistance Program

NORD and MedicAlert Foundation have teamed up on a new program to provide protection to rare disease patients in emergency situations.

Learn more https://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/

Rare Disease Educational Support Program

Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORD’s mission.

Learn more https://rarediseases.org/patient-assistance-programs/rare-disease-educational-support/

Rare Caregiver Respite Program

This first-of-its-kind assistance program is designed for caregivers of a child or adult diagnosed with a rare disorder.

Learn more https://rarediseases.org/patient-assistance-programs/caregiver-respite/

Patient Organizations

NORD Breakthrough Summit | Rare Disease Conference