Hypersensitivity pneumonitis.

This article has presented an overview on hypersensitivity pneumonitis, with an emphasis on the immunopathogenic and pathologic features. The disease is related to an immune complex and cell-mediated mechanism. The lung tissue may show a variety of histopathologic changes, most notable being a relatively diffuse lymphocyte-plasma cell interstitial infiltrate in association with small non-necrotizing granulomas.