Diagnosis of acute pulmonary toxoplasmosis by visualization of invasive and intracellular tachyzoites in Giemsa-stained smears of bronchoalveolar lavage fluid.

Two patients with AIDS presented with pulmonary toxoplasmosis. Diagnosis was achieved by the visualization, in Giemsa-stained smears of bronchoalveolar lavage fluid, of tachyzoites of Toxoplasma gondii that were extracellular and in the process of invading or within pneumocytes. The intracellular localization of tachyzoites facilitated diagnosis by obviating potential confusion of extracellular tachyzoites with cellular debris or platelets.