Pulmonary histoplasmosis: unusual histopathologic findings.

Four patients with clinical diagnosis of interstitial lung disease (ILD) are presented. In these patients, lung biopsies revealed bronchocentric granulomatosis (BG), pulmonary alveolar proteinosis (PAP), diffuse alveolar damage (DAD), and in one biopsy, the clinical manifestations suggested tuberculous primo-infection with systemic dissemination. Three patients died without diagnosis. In all four cases, specific histological stains found Histoplasma capsulatum. Histoplasmosis may mimic other infectious or non-infectious pulmonary diseases, such as interstitial and granulomatous pulmonary disease. Therefore, the absolute need for identification of the organism by culture or special stains cannot be over-emphasized and may lead to a proper mycological diagnosis. This highlights the importance of differential diagnosis with systemic infectious diseases, especially in areas where deep-seated mycosis are endemic.