Purpose of review: Histologic examination and microbiologic cultures are the gold standards for the diagnosis of infectious granulomatous lung diseases. Although biopsies require invasive procedures, they often yield information that cannot be obtained by other methods. The aims of this article are to outline the major infections that cause granulomatous inflammation in the lung and to familiarize clinicians with the utility of histologic examination in their diagnosis.
Recent findings: The histopathologic features of acute pulmonary histoplasmosis and granulomatous Pneumocystis pneumonia have been described in detail, the relative contributions of histology and microbiologic cultures in the diagnosis of blastomycosis have been delineated, and Cryptococcus gattii has emerged as a significant cause of granulomatous pulmonary nodules.
Summary: The major infectious causes of granulomatous lung disease are mycobacteria and fungi. Histologic examination is particularly important in the diagnosis of pulmonary granulomatous infections when clinical, radiologic and serologic findings are nonspecific. Histology and microbiology play complementary but distinct roles in diagnosis. For organisms that grow slowly in cultures, histology has the additional advantage of being able to provide a rapid diagnosis.