Abstract
BACKGROUND Pulmonary thromboembolism (PTE) sometimes leads to a shock state and sudden death due to acute massive pulmonary arterial thrombosis. The origins of pulmonary arterial thrombi are varied, but most arise from deep vein thrombosis. We herein presented a very rare cause of PTE due to paradoxical embolism caused by arteriovenous fistula from common iliac artery to common iliac vein. CASE REPORT A 74-year-old man was admitted because of increasing dyspnea on exertion. The diagnosis of idiopathic pulmonary fibrosis was made and corticosteroid therapy was started. On the 5th hospital day, the patient suddenly developed cardiopulmonary arrest and died despite cardiopulmonary resuscitation. An autopsy revealed that the left main pulmonary artery was occluded by a massive but organized thrombus that was similar to an arterial thrombus in the right common iliac artery. On histopathological examination, the emboli in the pulmonary artery demonstrated characteristics similar to thrombus in the common iliac artery. This suggested that the emboli had passed through the arteriovenous fistula from the right common iliac artery to the common iliac vein. CONCLUSIONS This is a very rare cause of fatal paradoxical pulmonary thromboembolism. Paradoxical emboli passing through arteriovenous fistula from the right common iliac artery to the common iliac vein are a rare cause of PTE.