Presentation of Superior Vena Cava Syndrome as a Consequence of Fibrosing Mediastinitis.

Fibrosing mediastinitis (FM) is a rare inflammatory reaction within the mediastinum that causes diffuse fibrosis and can lead to compression of vascular structures in the thoracic and cervical regions. While typically benign and indolent, significant progression can lead to obstruction of vital organs, causing conditions like superior vena cava (SVC) syndrome, pulmonary hypertension, and potentially fatal right-sided heart failure. The clinical presentation often mimics malignancy, which necessitates exclusion. FM is a rare condition, with idiopathic cases being even rarer. While histoplasmosis or tuberculosis infections are common causes of FM in the US, idiopathic forms such as IgG4-related FM can also occur.