[Deep venous thrombosis caused by congenital inferior vena cava agenesis].

Congenital agenesis of the inferior vena cava, although rare, is found preferentially in young patients with proximal deep venous thrombosis. Exact diagnosis can be made thanks to enhanced computed tomography scan and/or magnetic resonance imaging, while Doppler ultrasonography is insufficient to establish an inferior vena cava malformation. A consensus has not yet been established for the treatment but lifelong anticoagulation with elastic stocking support to prevent post-thrombotic syndrome is commonly considered in most cases. We report a case of an unprovoked deep venous thrombosis caused by a congenital agenesis of the inferior vena cava localized to the infrarenal segment, in a 24-year-old man. An anticoagulation with low molecular weight heparin was started and prolonged oral anticoagulation was prescribed. In the absence of the usual thrombotic risk factors, the presence of an inferior vena cava anomaly should be considered.