Infectious and inflammatory diseases.

The systemic conditions described in this paper are (1) sarcoidosis, (2) tuberculosis, (3) toxoplasmosis, and (4) histoplasmosis. The lung is the primary target organ of granulomatous involvement for each of these disorders. This and other similarities may confuse the diagnostic picture; however, appropriate understanding of clinical, epidemiologic, pathophysiologic, immunologic, radiologic, and serologic features assists in clearly establishing a diagnosis. The goals of this paper are to help the clinician develop a working knowledge of these four conditions, as well as an understanding of which tests are appropriate to order, how to interpret their results, and which treatment and management strategies to consider.