Imaging of pediatric mediastinal histoplasmosis.

Histoplasmosis can present a diagnostic dilemma if unusually large masses of lymph nodes, invasive mediastinal fibrosis, or pericarditis result from the infection. These rare, late sequelae are often first suspected from findings on chest radiographs obtained for unrelated reasons. Organisms are not always evident at histologic analysis at this stage. Mediastinal granulomas consist of lobulated masses of enlarged lymph nodes with central caseation, a peripheral thin capsule, and, occasionally, calcification. The mass does not invade or compromise adjacent anatomic structures. Mediastinal fibrosis invades and can seriously compromise the function of the tracheobronchial tree, superior vena cava, pulmonary arteries and veins, and esophagus; its symptoms mimic those of many other disorders. Pericarditis is commonly accompanied by pericardial effusion, pneumonia, and adenopathy. Although the radiologic findings of these conditions are nonspecific, they can be used with the clinical findings to suggest a diagnosis. Complications of histoplasmosis should be included in the differential diagnosis for patients residing in areas endemic to Histoplasma capsulatum.