Case #282 – August, 2010

A 49-year-old man with AIDS was admitted to the hospital for complaints of a persisting fever and dry cough. A chest radiograph showed bilateral infiltrate. A sputum specimen was collected and stained with Giemsa, but no parasites were observed. A lung biopsy was obtained, sectioned, and stained with both methenamine silver and hematoxylin and eosin (H&E) stains. Figures A and B show what was observed at 500x magnification on one of the stained sections. What is your diagnosis? Based on what criteria?

Figure A

Figure B

This was a case of pneumonia caused by Pneumocystis jirovecii (previously classified as Pneumocystis carinii). Because this case showed images taken from a lung biopsy stained with a combination of hematoxylin and eosin (H&E) and methenamine silver, only the cyst walls stained black and intracystic bodies are not visible.