Refractory chylothorax caused by massive thymic hyperplasia in an infant: thoracoscopic thymectomy

Introduction: Spontaneous chylothorax in infancy is most commonly associated with congenital lymphatic malformations or iatrogenic injury. Massive thymic hyperplasia (MTH) causing refractory chylothorax through extrinsic compression is rare. We report an infant with severe chylothorax secondary to MTH, successfully managed with thymectomy. Case presentation: A 2-month-old female infant presented with respiratory distress and recurrent pleural effusions. Thoracentesis yielded milky chylous fluid with a triglyceride level of 19.8 mmol/L. Chest MRI demonstrated a homogeneous anterior mediastinal mass (24 × 23 × 22 mm 3 ) compressing the left subclavian vein. After the failure of conservative management, including a medium-chain triglyceride (MCT) diet and intravenous octreotide, the patient underwent video-assisted thoracoscopic thymectomy. Histopathology confirmed benign thymic hyperplasia. Clinical discussion: MTH may cause significant compression of mediastinal structures, impairing lymphatic drainage. When conservative treatment fails in the presence of persistent structural obstruction, surgical decompression is indicated to prevent immunological and nutritional complications. Conclusion: MTH is a rare cause of refractory chylothorax in infancy. In cases with persistent mechanical obstruction, surgical thymectomy provides an effective and definitive treatment.