A 48 year old woman presents with progressive dyspnea for 1 week. There was no cough or chest pain. She was diagnosed with metastatic cancer of the right breast 1 year ago, for which a radical mastectomy was performed. She completed her 6th cycle of chemotherapy three months ago. On admission, her oxygen saturation was 82%, which improved to 99% with high flow oxygen. A full blood count and chest x-ray are normal.
There are patchy areas of ground-glass attenuation, in a background of interlobular septal thickening.
Gram stain: negative Giemsa & Methenamine Silver stains: negative Culture results will be available in 3 days.
On room air: pH: 7.46 (7.35 - 7.45) pO2: 68 mmHg (> 79 on room air) PCO2: 32 mmHg (35 - 45) HCO3: 23 mmol/l (24 - 32)
A Giemsa stain reveals multiple thick walled cysts and pleomorphic trophozoites with reddish nuclei and bluish cytoplasm. The cyst walls are stained by Methenamine Silver. Blood is not seen in any lavage aliquots.