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PJP Pneumonia — RACP Adult Medicine MCQ

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ModerateInfectious DiseasesPJP PneumoniaRACP Adult Medicine

A 45-year-old man with newly diagnosed HIV (CD4 120 cells/µL) develops progressive shortness of breath and dry cough. CXR shows bilateral perihilar interstitial infiltrates. SpO₂ is 88% on room air. LDH is elevated. What is the most likely diagnosis and first-line treatment?

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Correct answer: A — Pneumocystis jirovecii pneumonia – IV trimethoprim-sulfamethoxazole plus prednisolone

PJP (Pneumocystis jirovecii pneumonia) presents in severely immunosuppressed HIV patients (CD4 <200) with subacute dyspnoea, dry cough, bilateral perihilar infiltrates, elevated LDH, and hypoxia. First-line treatment is IV TMP-SMX (15–20 mg/kg/day of TMP component) for 21 days. Adjunctive prednisolone is indicated when PaO₂ <70 mmHg (or A-a gradient >35 mmHg), as it reduces mortality (Bozzette trial). ART should be commenced within 2 weeks.

Reference: eTG – 2025 – Antibiotic Guidelines; ASHM – 2024 – HIV Management Guidelines