1. Pulmonary arteriovenous malformation is an abnormal communication between the pulmonary artery and the pulmonary vein. It presents as an isolated pulmonary lesion or as part of a hereditary syndrome called hemorrhagic telangiectasia (70%). It usually presents between the fourth and sixth decades with epistaxis, dyspnea, hemoptysis or stroke. We describe a patient who developed an enlarging lung mass and hemoptysis secondary to pulmonary arteriovenous malformation. Her White blood cell count was elevated. Chest x-ray showed right perihilar opacity (Figure 1). Antibiotics were given for empirical treatment of community acquired pneumonia. CT scan of the chest revealed right lower lobe consolidation and right upper lobe lung mass measured 3.0 x 4.1 cm (Figure 2), a much smaller lesion identified in this location 3 years earlier. 3D rendering technique showed arteriovenous malformation supplied by the right upper lobe pulmonary artery and drained by the upper lobe pulmonary vein (Figure 3). Pulmonary artery angiogram with catheterization was performed. A 2 cm aneurismal dilatation of the pulmonary artery malformation with early venous drainage was confirmed (Figure 4). Patient underwent successful coil embolization of the right pulmonary arteriovenous malformation (Figure 5). Pulmonary arteriovenous malformation is rare, but potentially life-threatening disease presents usually as a lung nodule or mass. Complications include massive hemoptysis, hemothorax, hypoxemia leading to acute respiratory distress, paradoxical embolization with hemorrhagic cerebral vascular accident and cerebral abscesses. CT-scan of the chest is highly sensitive to detect and localize the pulmonary arteriovenous malformation. Pulmonary angiogram is the gold standard in the diagnosis. Physicians should consider pulmonary arteriovenous malformation in patients with hemoptysis. These patients can have a catastrophic rapidly progressive course. Such patients can respond well to catheter embolization done by an interventional radiologist. Pulmonary Arteriovenous Malformation Presenting As an Enlarging Lung Mass and Hemoptysis Juan Rojas, MD; Bassel Ericsoussi, MD; Bashar Chihada Alhariri, MD; Mohammed Sahloul, MD, FCCP Internal Medicine, University of Illinois, Advocate Christ Medical Center, Oak Lawn, IL, USA INTRODUCTION HISTORY An 87 year old white man with a past medical history of coronary artery disease, congestive heart failure, hypertension and morbid obesity presented with progressive dyspnea associated with fever and productive cough of yellowish sputum mixed with blood for 2 days. Physical exam was only notable for bronchial breathing and crackles in the right lung base. HOSPITAL COURSE Figure 1. Chest X-Ray Ill-defined right perihilar opacity. Figure 2. Chest CT-Scan with Contrast An enhancing nodular 3.0 x 4.1 cm anteromedial lung mass, most likely represents a pulmonary arteriovenous malformation, as there are serpiginous feeding and draining vessels in the vicinity. Figure 3. Chest CT-Scan 3D Rendering Aneurysmal dilatation in the superior mediastinum in substernal area which is apparently supplied by the upper lobe pulmonary artery on the right and also drained via upper lobe pulmonary vein on the right. Overall size measures 40.1 mm in width x 40.7 mm in height. Figure 4. Pre-Embolization Right pulmonary Artery Angiogram 2 cm aneurysmal dilatation of the pulmonary arteriovenous malformation, with early venous drainage through the pulmonary arterial venous malformation. Figure 5. Post-Embolization Right pulmonary Artery Angiogram Multiple metallic coils are visualized within the feeding vessel into the pulmonary arteriovenous malformation. No flow of contrast is visualized in the feeding arterial vessel, distal to the coils. DISCUSSION