Incidental discovery of duplicated superior vena cava in a patient with thymoma and myasthenia gravis: a case report

Myasthenia gravis (MG) is an autoimmune neuromuscular junction disorder frequently associated with thymic abnormalities, particularly thymoma. Duplicated superior vena cava (DSVC) is an uncommon congenital venous anomaly with potential implications for central venous access and mediastinal surgery. Its incidental coexistence with thymoma-associated MG is rare and underscores the importance of recognizing vascular variants before surgical intervention. A 21-year-old Arab woman presented with progressive bilateral ptosis, diplopia, mild dysphagia, and generalized fatigability over 4 months. Neurological evaluation confirmed MG with positive anti-acetylcholine receptor antibodies. Chest computed tomography revealed an anterior mediastinal mass suspicious for thymoma and duplication of the superior vena cava. Medical treatment with pyridostigmine and corticosteroids resulted in symptomatic improvement. Following preoperative optimization, she underwent video-assisted thoracoscopic thymectomy. The anterior mediastinal mass was completely excised, and intraoperative inspection confirmed DSVC, which required no intervention. Histopathological examination demonstrated a well-encapsulated type AB thymoma without capsular invasion. The immediate postoperative course was uneventful, and she was discharged in stable condition. At 1-month surgical follow-up, she remained well with no surgical complications; a formal neurological reassessment was not available. This case highlights the rare coexistence of MG, thymoma, and DSVC. Preoperative recognition and documentation of DSVC are clinically important for operative planning and may reduce the risk of vascular injury during mediastinal surgery while also informing future central venous or transvenous procedures.