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Vascular · OvergrowthICD-10 Q87.2

Klippel-Trénaunay syndrome

KTS · capillary-lymphatic-venous malformation with overgrowth · CLVM

Klippel-Trénaunay syndrome (KTS) is a sporadic capillary-lymphatic-venous malformation with associated limb overgrowth, classically affecting one lower limb. The triad is (1) port-wine stain (capillary malformation), (2) venous and / or lymphatic malformation, and (3) bony / soft-tissue overgrowth. The principal pathogenic mutation is a somatic mosaic activating mutation in PIK3CA (PROS — PIK3CA-related overgrowth spectrum). UK ISSVA classification places KTS within the slow-flow vascular malformation overgrowth syndromes.

CurrentLast reviewed 16 May 2026

Genetics

  • Sporadic; somatic mosaic activating mutation in PIK3CA (p110α PI3K subunit).
  • Mutations also underlie CLOVES, megalencephaly-capillary-malformation, fibroadipose hyperplasia — collectively PIK3CA-related overgrowth spectrum (PROS).
  • Distribution is segmental / geographic, reflecting somatic clonal mosaicism.

Clinical features

  • Classic triad:
    1. Capillary malformation (port-wine stain) — affecting limb, often with sharp midline cutoff.
    2. Venous / lymphatic malformation — varicosities, prominent lateral veins (vein of Servelle), lymphatic vesicles, chylous reflux.
    3. Soft-tissue and / or bony overgrowth of affected limb.
  • Limb-length / circumference discrepancy; can be subtle or marked.
  • Complications:
    • Recurrent cellulitis.
    • Venous thromboembolism — increased risk; pulmonary embolism reported.
    • Lymphorrhoea, lymphatic vesicle bleeding.
    • Pelvic / visceral involvement: bladder, rectal, vaginal malformations.
  • Parkes-Weber syndrome is a related fast-flow variant with arteriovenous fistulae.

Workup

  • MRI of affected limb: characterises vascular components, soft tissue, bone.
  • Doppler USS for slow vs fast flow; venous patency.
  • Plain radiographs for limb-length, bone overgrowth.
  • Pelvic / abdominal MRI if pelvic involvement suspected.
  • Coagulation screen and D-dimer (chronic localised intravascular coagulopathy common with venous malformations).
  • Genetic testing — somatic biopsy from affected tissue rather than blood (deep sequencing required, since mosaic).

Management

  • Multidisciplinary vascular anomalies clinic (vascular surgery, interventional radiology, plastic surgery, dermatology, orthopaedics, haematology, genetics, psychology).
  • Compression therapy for venous malformation symptoms.
  • Sclerotherapy (foam) for venous and lymphatic malformations.
  • Laser (pulsed dye laser) for capillary malformation.
  • Surgical debulking in selected cases.
  • Limb-length: orthopaedic management — shoe raise, epiphysiodesis.
  • Sirolimus: mTOR inhibitor; emerging evidence for vascular malformations, particularly lymphatic / venous components.
  • Alpelisib (PI3K inhibitor) — emerging for PIK3CA-related overgrowth spectrum (compassionate use; clinical trials).
  • VTE prophylaxis: discuss for surgery, immobility, long flights; LMWH considered for high-risk venous malformations.
  • Psychological support for limb and body-image issues.

References

  1. Servelle M. Klippel and Trénaunay's syndrome: 768 operated cases. Ann Surg. 1985;201:365-373.
  2. Vahidnezhad H et al. Klippel-Trenaunay syndrome belongs to the PIK3CA-related overgrowth spectrum (PROS). Exp Dermatol. 2016;25:17-19.
  3. Adams DM et al. Efficacy and safety of sirolimus in the treatment of complicated vascular anomalies. Pediatrics. 2016;137:e20153257.
  4. ISSVA classification of vascular anomalies. Boston: ISSVA; 2018.
  5. Venot Q et al. Targeted therapy in patients with PIK3CA-related overgrowth syndrome. Nature. 2018;558:540-546.

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