Adventitial cystic disease of the femoral vein in a 5-year-old boy mimicking deep venous thrombosis.

Adventitial cystic disease of the vein is a rare vascular anomaly with 32 reported cases. A 5-year-old boy initially presented with painless leg swelling. He was misdiagnosed with deep vein thrombosis and treated with 3 months of warfarin. When swelling failed to improve, a magnetic resonance venogram showed a mural cystic lesion of the left common femoral vein. In the operating room, the cyst was excised, relieving the obstructive effect and restoring flow. The swelling resolved within days. This is the first reported case of adventitial cystic disease of the vein occurring in a pediatric patient.