Klippel-Trénaunay syndrome

Last revised by Rohit Sharma on 5 Nov 2023

Klippel-Trénaunay syndrome is a very rare congenital disorder that is characterized by a triad of venous malformations, cutaneous capillary malformations, and limb overgrowth. It is considered an angio-osteo-hypertrophic syndrome.

The name Klippel-Trénaunay-Weber syndrome is misleading as the current consensus uses two different names to denote two different syndromes. However, they are not always consistently addressed as distinct entities in the literature:

  • Klippel-Trénaunay syndrome is used in this article, whenever possible

  • Parkes Weber syndrome with true arteriovenous (AV) shunting

Most cases of Klippel-Trénaunay syndrome are sporadic and there is no recognized gender or racial predilection. The prevalence of Klippel-Trénaunay syndrome (including Parkes Weber syndrome) is ~1:100,000 11.

Klippel-Trénaunay syndrome classically comprises a triad of:

  • cutaneous capillary malformations: port wine nevi 

  • limb overgrowth: bony or soft tissue hypertrophy of an extremity (localized gigantism)

  • varicose veins or venous malformations of unusual distribution

The diagnosis of Klippel-Trénaunay syndrome is usually made when any two of the three features are present. Patients usually present in infancy. Features are often unilateral and typically affect one limb 2; capillary malformations may be absent in the atypical form 14. It may be diagnosed in utero 11.

Enlargement of the extremity consists of bone elongation, circumferential soft-tissue hypertrophy or both. This often manifests as leg-length discrepancy, although any limb may be affected. Hyperostosis frontalis interna has also been associated with Klippel-Trénaunay syndrome 23.

This is the most common cutaneous manifestation of Klippel-Trénaunay syndrome. Typically, capillary malformations involve the enlarged limb, although skin changes may be seen on any part of the body. The lower limb is the affected site in ~95% of patients.

Present in a majority of patients with Klippel-Trénaunay syndrome, commonly located on the lateral aspect of the affected limb/leg 18 (and in some contradiction to common vena-saphena-magna varicosity). There may be persistence of embryonic veins, of which the lateral marginal vein (the vein of Servelle) has been the most typical finding (68-80% of patients) 22.

Venous malformations can occur in both the superficial and deep venous systems. Superficial venous abnormalities range from ectasia of small veins to persistent embryological veins and large venous malformations. Deep venous abnormalities include aneurysmal dilatation, aplasia, hypoplasia, duplications, and venous incompetence.

Rectal and bladder hemorrhage are serious complications of pelvic vascular malformations and have been reported in 1% of cases 10. Vascular malformations can involve the:

  • gastrointestinal tract (20%)

    • bleeding is the most common symptom and range from occult bleeding to massive, life-threatening hemorrhages and consumptive coagulopathy

    • the most frequently reported sites are the distal colon and rectum

    • upper gastrointestinal bleeding from jejunal hemangiomas may also occur 19

  • genitourinary tract

    • involved in more severe cases

    • the absence of severe limb varicosities or venous malformations does not preclude the presence of pelvic involvement

    • gross hematuria, which is recurrent and painless, is usually the first clinical sign of bladder involvement and frequently manifests early in life

    • renal hypertrophy and venous enlargement may occur ipsilaterally to the affected side 15

    • vascular malformations are often located on the anterior bladder wall and dome

    • the trigone and bladder neck are rarely involved

    • genital lesions usually do not cause clinical problems for patients with Klippel-Trénaunay syndrome; however, some patients who report erectile dysfunction have abnormal penile veins

  • spleen

These are usually secondary to leg-length difference 13:

The following levels of severity of Klippel-Trénaunay syndrome have been suggested 13:

  1. venous/phlebectasic dysplasias

  2. arterial dysplasias

  3. arterial and associated venous dysplasias

  4. mixed angiodysplasias: atypical form of Klippel-Trénaunay syndrome

Most cases are considered sporadic. However, some of the possible differential diagnoses may have familial predispositions 16.

May show a combination of any of the above mentioned clinical features.

On conventional radiography, bone elongation contributing to leg length discrepancy, soft-tissue thickening, or calcified phleboliths may be seen.

Prenatal ultrasound may diagnose Klippel-Trénaunay syndrome as early as the 15th week of gestation, based on limb hypertrophy and associated subcutaneous cystic lesions. 3D ultrasound may reveal leg width difference. Possible additional features include 11,16:

T2-weighted MR images may show malformed venous and lymphatic lesions as areas of high signal intensity.

MR imaging depicts deep extension of low-flow vascular malformations into muscular compartments and the pelvis and their relationship to adjacent organs as well as bone or soft tissue hypertrophy.

Typical angiographic findings, which may also be seen on contrast-enhanced CT-scan or MRI, include lower leg superficial varicoid drainage without a deep venous system. The marginal vein of Servelle is a pathognomonic finding (a subcutaneous vein found in the lateral calf and thigh) 9.

Treatment in a majority of patients is conservative and includes application of graded compressive stockings or pneumatic compression devices to the enlarged extremity. Percutaneous sclerosis of localized venous malformations or superficial venous varicosities may be indicated in some patients. Surgical treatment may include epiphysiodesis to control leg length discrepancy, excision of soft tissue hypertrophy, and stripping of superficial varicose veins.

  • thrombophlebitis of the affected limb

  • venous thromboembolism 21

  • gastrointestinal or genitourinary hemorrhage if there is visceral involvement (see above)

  • If capillary malformations are large enough, they may sequester platelets, possibly leading to the Kasabach-Merritt syndrome (consumptive coagulopathy)

In 1900, the French physicians Klippel and Trénaunay first described a syndrome characterized by a capillary nevus of the affected extremity, lateral limb hypertrophy, and varicose veins. In 1918, Parkes Weber noted the association of this triad with arteriovenous fistulas 10-12.

Differentials for intrauterine imaging findings may include 11:

In children and young adults consider:

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