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Figure 1. A 45-year-old man with the acquired immunodeficiency syndrome presented with night sweats, fatigue, cachexia, and a productive cough. He had a fever (temperature, 40°C), tachycardia (heart rate, 136 per minute), a leukocyte count of 2.5x103 per cubic millimeter, and hypotension (blood pressure, 90/50 mm Hg). A chest x-ray film revealed an infiltrate in the right lower lobe. A peripheral-blood smear (Wright's stain, x1000) obtained on admission showed a monocyte with a grossly distorted nucleus and numerous intracellular yeast-like organisms 2 to 4 µm in diameter with eccentric chromatin. The organisms were surrounded by an artifactual pseudocapsule caused by cytoplasmic shrinkage. These features are diagnostic of Histoplasma capsulatum. Of 200 neutrophils or monocytes examined, 26 (13 percent) contained these organisms, and the intracellular burden ranged from 1 to 20 organisms. H. capsulatum was isolated from cultures of blood obtained on admission. The patient was treated with amphotericin B, but his condition deteriorated and he died of septic shock two weeks later. H. capsulatum is acquired by the inhalation of conidia or mycelial fragments. Reactivation of a latent infection is possible and may explain the occurrence of histoplasmosis in this patient, who was originally from Alabama, an area in which the fungus is endemic.
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