Mediastinal IgG4-Related Disease Presenting As Superior Vena Cava Syndrome.

IgG4-related disease (IgG4-RD) was first identified as a systemic condition in 2003 when extra-pancreatic manifestations were identified in patients with autoimmune pancreatitis. Its peak incidence occurs in the fifth or sixth decades of life. Isolated extra-aortic mediastinal involvement is extremely rare. We report a case of isolated extra-aortic mediastinal IgG4-RD encasing the superior vena cava (SVC), manifesting as SVC syndrome in a 25-year-old man with no personal or family history of autoimmune disease. Resection with SVC reconstruction was performed.