An HIV-infected patient with CD4 count 80 cells/uL develops progressive dyspnoea and dry cough. Chest radiograph shows bilateral diffuse interstitial infiltrates. Bronchoalveolar lavage stained with Gomori methenamine silver reveals cup-shaped cysts. Which drug is the treatment of choice?
- A Trimethoprim-sulfamethoxazole ✓
- B Amphotericin B deoxycholate
- C Itraconazole
- D Flucytosine
Correct answer: A. Trimethoprim-sulfamethoxazole
Explanation
Pneumocystis jirovecii pneumonia occurs when CD4 counts fall below 200 cells/uL and presents with diffuse bilateral interstitial infiltrates. Although reclassified as a fungus based on ribosomal RNA sequencing, it does not respond to conventional antifungal agents because it lacks ergosterol. Trimethoprim-sulfamethoxazole, targeting dihydrofolate reductase and dihydropteroate synthase, remains the treatment of choice, with pentamidine or atovaquone as alternatives.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.