Bilateral Klippel–Trénaunay Syndrome in an Adolescent Male with Deep Vein Thrombosis Complication: A Case Report and Literature Review

Abstract

Introduction: Klippel–Trénaunay syndrome (KTS) is a rare congenital vascular disorder characterized by mixed malformations of capillaries, veins, and lymphatic systems, often accompanied by soft tissue or bone hypertrophy. Although classically described as a unilateral condition, bilateral manifestations and axillary lymphatic involvement can occur, presenting significant diagnostic challenges for radiologists and clinicians.

Case Report: We report a case of a 15-year-old male with progressive bilateral lower limb swelling since infancy. The patient experienced intermittent pain, redness, and episodes of inability to walk. Physical examination confirmed massive bilateral soft tissue edema and a new, rapidly growing left axillary mass suspected to be a lymphatic malformation. Computed Tomography Angiography (CTA) and Venography (CTV) detected extensive deep vein dilatation and thrombosis in the right femoral vein, without evidence of high-flow arteriovenous fistulas, thus confirming a diagnosis of KTS and excluding Parkes Weber syndrome.

Discussion: This case highlights an unusual bilateral presentation of KTS, which occurs in less than 10% of cases, likely due to an early post-zygotic somatic mutation. The finding of dilated deep veins (femoral vein diameter 9.57 mm) contrasts with the classic finding of venous hypoplasia. The left axillary mass is consistent with a macrocystic lymphatic malformation, a known component of the capillary-lymphatic-venous malformation (CLVM) spectrum. The absence of early venous filling on CTA successfully differentiated low-flow KTS from high-flow Parkes Weber syndrome, guiding appropriate management toward anticoagulation and compression therapy.

Conclusion: KTS is a progressive, complex disorder requiring a multidisciplinary approach. Integration of clinical findings with multimodal vascular imaging is crucial for diagnosis, excluding differentials, and detecting complications such as deep vein thrombosis. Current management focuses on anticoagulation for thrombosis and conservative measures with compression stockings to manage chronic venous insufficiency. An in-depth understanding of the molecular pathogenesis of PIK3CA mutations opens opportunities for future targeted therapy.