Deep vein thrombosis as a presenting symptom of congenital interruption of the inferior vena cava.

Infrahepatic interruption of the inferior vena cava is a congenital anomaly, resulting in venous drainage of the lower extremities by way of a compensatory enlarged vena azygos system. We report the case of a 37-year-old male who presented with symptoms of deep vein thrombosis of the entire right lower extremity. A right-sided mediastinal mass on the chest X-ray was mistaken for a haematological malignancy but proved later to represent an enlarged azygos vein. The case illustrates that in a case of deep vein thrombosis, especially in younger patients, interruption of the inferior vena cava should be considered. A right-sided paratracheal mass on the chest X-ray may give a clue in making the correct diagnosis.