Superficial venous malformations (SVMs) are rare congenital anomalies that present as bluish masses. These masses may be focal, with limited skin involvement, or segmental, with more extensive involvement. They may be associated with syndromic conditions such as blue rubber nevus syndrome.

SVMs are characterised by a progressive worsening course, with repeated episodes of superficial venous thrombosis occurring. These episodes become more frequent over time, causing acute, intense and often highly debilitating pain.

To limit progression and in cases of functional impairment, long-term treatments may be offered. These include venous compression, targeted therapies such as mTOR inhibitors, and, where possible, surgical treatment or sclerotherapy.

However, the management of intra-SVM superficial venous thrombosis is not currently standardised, especially in the pediatric population. This study aims to evaluate the benefits of Acetylsalicylic acid (ASA) as an add-on treatment to local non-steroidal anti-inflammatory drug for the management of thrombotic episodes in superficial venous malformations in children aged 6 to 17 years.

Inclusion Criteria:

• Patients aged 6 to 17 years
• Weight ≥ 20 kg
• Isolated or combined superficial venous malformation, confirmed by imaging, with the presence of phleboliths indicating the occurrence of previous superficial venous thrombosis
• Complicated by acute thrombotic episodes (2 or more in the previous 12 months)
• Written consent of the child's legal representatives or of the participant if over 18 years of age
• Affiliation of a social security scheme
• Highly effective contraception for young women of childbearing age

Exclusion Criteria:

• Patients with deep or syndromic venous malformation
• Patients with known G6PD deficiency
• Patients with known mastocytosis
• History of hemarthrosis
• Simultaneous participation in another biomedical study
• Constitutional or acquired haemostasis pathology
• Current treatment affecting haemostasis (anticoagulants, platelet anti aggregants, oral NSAIDs)
• Frequent bleeding (epistaxis, other) requiring management
• Basic treatment of venous malformation (mTOR inhibitor)
• Active neoplasia or infection (altered coagulation balance)
• Known allergy to acetylsalicylic acid
• Injured skin, whatever the lesion: oozing dermatitis, eczema, infected lesions, burns or wounds
• Pregnant and breastfeeding women
• Severe renal insufficiency, severe hepatic insufficiency, severe uncontrolled cardiac insufficiency
• Methotrexate ≥ 20 mg/week