Mediastinal histoplasmosis

Mediastinal histoplasmosis is now known to exist in two forms: an early or acute stage characterized by the presence of caseous or fibrocaseous lymph nodes within the mediastinum, and a late or chronic stage by fibrous mediastinitis. The term mediastinal granuloma was originally introduced to define the collection of caseous mediastinal nodes at a time when no specific organisms could be identified. Mediastinal granuloma was therefore considered an entity in itself of no known etiology. However, recent experience as well as improved staining techniques have shown histoplasmosis as the cause of mediastinal granuloma in approximately 85% of the cases and fibrous mediastinitis as the end stage of this disease spectrum. This paper will discuss the radiographic and clinical presentations of mediastinal granuloma and its evolution to fibrous mediastinitis. The findings vary according to the stage and depend upon which mediastinal structures are involved.