An Uncommon Cause of Massive Hemothorax: Pulmonary Arteriovenous Malformation in the Right Middle Lobe.

Pulmonary arteriovenous malformations (PAVMs) are rare vascular anomalies that can lead to severe complications when ruptured. We report the case of a 65-year-old active smoker who presented to the emergency department with acute pleuritic chest pain, severe dyspnea, and hypoxemia. Chest CT revealed a large PAVM in the right middle lobe, associated with massive hemothorax and a small pneumothorax. The patient had no history of hereditary hemorrhagic telangiectasia. Initial management included pleural drainage and endovascular embolization with a 16 mm Amplatzer™ device. Due to persistent respiratory failure and high risk of rebleeding, a right middle lobectomy was subsequently performed. Intraoperative findings confirmed a partially thrombosed AVM and correct device placement. Postoperative recovery was uneventful, with no recurrent bleeding. This case highlights a rare cause of spontaneous massive hemothorax requiring combined endovascular and surgical management, emphasizing the importance of early diagnosis and multidisciplinary care in idiopathic PAVMs.