A 48-year-old HIV-positive man (CD4 count 45 cells/μL) has fever, dry cough, and progressive dyspnoea. CXR shows bilateral perihilar interstitial infiltrates. LDH is 580 U/L. Bronchoalveolar lavage with Gomori-methenamine silver (GMS) stain shows cysts. The MOST appropriate treatment regimen is:
- A Amphotericin B deoxycholate
- B Pentamidine alone as first-line
- C Trimethoprim-sulfamethoxazole (TMP-SMX) 15–20 mg/kg/day of TMP component for 21 days; add adjunctive prednisone if PaO2 < 70 mmHg ✓
- D Fluconazole 800 mg loading dose
Correct answer: C. Trimethoprim-sulfamethoxazole (TMP-SMX) 15–20 mg/kg/day of TMP component for 21 days; add adjunctive prednisone if PaO2 < 70 mmHg
Explanation
This presentation describes Pneumocystis jirovecii pneumonia (PCP), the most common AIDS-defining opportunistic infection at CD4 < 200 cells/μL. GMS stain demonstrates the characteristic cysts. TMP-SMX is first-line treatment (15–20 mg/kg/day of TMP component in 3–4 divided doses) for 21 days. Adjunctive corticosteroids (prednisone 40 mg twice daily, tapering over 21 days) are indicated when PaO2 < 70 mmHg on room air or A-a gradient > 35 mmHg, as shown by multiple RCTs to reduce respiratory failure and mortality. Pentamidine is used for TMP-SMX intolerance.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.