Chylothorax Secondary to Behçet's Disease: A Case Report.

Chylothorax is an uncommon cause of pleural effusion and is most frequently associated with trauma or malignancy. Its occurrence in Behçet's disease (BD) is exceptionally rare and is usually related to extensive central venous thrombosis causing obstruction of the thoracic duct. We report the case of a 35-year-old woman with a five-year history of BD who presented with progressive dyspnea, dry cough, and mild hemoptysis. Chest computed tomography (CT) revealed extensive thrombosis of the superior vena cava extending to both brachiocephalic veins and the right subclavian vein, associated with large bilateral pleural effusions. Diagnostic thoracentesis yielded milky pleural fluid with elevated triglyceride levels, confirming bilateral chylothorax. Other potential causes, including pulmonary embolism, pulmonary artery aneurysm, malignancy, chylopericardium, and chyloperitoneum, were excluded. The patient was treated with therapeutic anticoagulation, high-dose corticosteroids, intravenous cyclophosphamide, repeated therapeutic thoracentesis, and nutritional support with dietary fat restriction. Clinical and radiological outcomes were favorable, with complete resolution of dyspnea and marked regression of the pleural effusions. Chylothorax is a rare but important thoracic manifestation of BD. In patients presenting with unexplained pleural effusion and central venous thrombosis, BD should be considered among the differential diagnoses. Early recognition and prompt immunosuppressive therapy, combined with appropriate management of the pleural effusion, are essential to achieve favorable outcomes.