A 44-year-old man with a history of chronic granulomatous disease presented to the emergency department with a 1-day history of fever and shortness of breath. Physical examination showed only tachycardia and tachypnea, with lungs clear to auscultation. Chest radiograph showed diffuse, ill-defined micronodular opacities (Figure 1). The patient was treated with amoxicillin-clavulanic acid for presumed community-acquired pneumonia. He returned 5 days later with persistent fever, progressive dyspnea and hypoxia. Repeat chest radiograph showed substantial progression with new coarse interstitial infiltrates and ground glass opacities (Appendix 1, available at www. cmaj.ca/lookup/doi/10.1503/cmaj.220713/tab-related-content). The patient reported that the day before his symptom onset, he had been feeding hay to large animals at a livestock farm in rural Ontario.
We considered the following diagnoses: acute fungal (aspergillosis, histoplasmosis, blastomycosis) and bacterial (Q fever, nocardiosis)...