Segmental venous malformation

Segmental venous malformation is a type of slow-flow vascular malformation characterized by abnormally formed veins that are localized to a specific body segment or region. Unlike multifocal or diffuse venous malformations, segmental venous malformations are confined to a defined anatomical area, such as a limb, a portion of the trunk, or the head and neck region. These malformations are present at birth, although they may not become clinically apparent until later in infancy or childhood as they gradually enlarge. They are composed of dilated, thin-walled venous channels lined by endothelium and are thought to arise from errors in vascular development during embryogenesis. Clinically, segmental venous malformations present as soft, compressible, bluish masses beneath the skin that may swell with dependent positioning or Valsalva maneuver. They can cause pain, swelling, and functional impairment depending on their location and size. Involvement of deeper tissues including muscles and joints can lead to significant morbidity. Localized intravascular coagulopathy may occur within the malformation, leading to elevated D-dimer levels and risk of thrombosis. Phleboliths (calcified thrombi) are a characteristic finding on imaging. Treatment is guided by symptoms and functional impact. Conservative management includes compression garments and low-dose anticoagulation for pain related to localized intravascular coagulopathy. Sclerotherapy, in which a sclerosing agent is injected directly into the malformation to induce shrinkage, is a commonly used interventional approach. Surgical resection may be considered for well-circumscribed lesions or when sclerotherapy is insufficient. Many segmental venous malformations harbor somatic activating mutations in the TEK gene (encoding the TIE2 receptor) or in PIK3CA, which are involved in the PI3K/AKT signaling pathway. Targeted therapies such as sirolimus (an mTOR inhibitor) have shown promise in reducing symptoms and size of venous malformations in clinical studies.

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