A 50-year-old HIV-positive man (CD4 count 60 cells/μL) presents with 3 weeks of fever, dry cough, and exertional dyspnea. CXR shows bilateral perihilar interstitial infiltrates. LDH is markedly elevated at 720 U/L. SaO2 at rest is 91%. What is the most likely diagnosis and treatment of choice?
- A Pulmonary tuberculosis; start HRZE regimen
- B Community-acquired pneumonia; start amoxicillin-clavulanate
- C Pneumocystis jirovecii pneumonia; start trimethoprim-sulfamethoxazole (TMP-SMX) with adjunctive corticosteroids ✓
- D Cytomegalovirus pneumonitis; start IV ganciclovir
Correct answer: C. Pneumocystis jirovecii pneumonia; start trimethoprim-sulfamethoxazole (TMP-SMX) with adjunctive corticosteroids
Explanation
Pneumocystis jirovecii pneumonia (PCP) classically presents in patients with CD4 < 200 cells/μL with subacute onset of dyspnea, dry cough, bilateral interstitial infiltrates on CXR, and markedly elevated LDH. TMP-SMX (15–20 mg/kg/day trimethoprim component in divided doses for 21 days) is the treatment of choice. Adjunctive corticosteroids (prednisone) are indicated when PaO2 < 70 mmHg or A-a gradient > 35 mmHg to reduce lung inflammation and mortality.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.