Pneumocystis jirovecii pneumonia — DTM&H MCQ

Correct answer: B — High-dose co-trimoxazole with adjunctive corticosteroids

B. High-dose co-trimoxazole with adjunctive corticosteroids is correct. This HIV-positive man with a subacute (weeks-long) dry cough, exertional dyspnoea, hypoxia (SpO2 88 percent), bilateral interstitial shadowing on chest X-ray and a raised LDH has a classic presentation of Pneumocystis jirovecii pneumonia (PJP), the commonest AIDS-defining opportunistic infection in advanced, untreated HIV. High-dose co-trimoxazole (trimethoprim-sulfamethoxazole) is first-line treatment for PJP of any severity. Given the significant hypoxaemia (SpO2 under 92 percent on air is a widely used threshold, corresponding to moderate to severe disease), adjunctive corticosteroids are indicated because they reduce inflammation-driven deterioration during the first days of treatment and improve survival and reduce respiratory failure in this severity band. Why the other options are wrong: A. Azithromycin monotherapy: this macrolide targets atypical bacterial pathogens such as Mycoplasma or Legionella and has no reliable activity against Pneumocystis jirovecii, so it would leave the causative organism untreated. D. Isoniazid preventive therapy: this is prophylaxis against latent tuberculosis in people without active disease, not a treatment for an established, symptomatic opportunistic infection with hypoxia. E. Fluconazole induction therapy: fluconazole is an antifungal used for conditions like cryptococcal meningitis or oesophageal candidiasis; Pneumocystis is not susceptible to azoles. C. Artemether-lumefantrine: this is antimalarial therapy for confirmed Plasmodium infection; there is no history or feature here (fever, travel exposure, blood film) pointing to malaria, and it has no role in respiratory opportunistic infection. Key point: subacute hypoxic pneumonitis with bilateral interstitial infiltrates and raised LDH in advanced untreated HIV should trigger empirical high-dose co-trimoxazole, adding corticosteroids once hypoxaemia meets the moderate-to-severe threshold.

Reference: BHIVA Guidelines for the treatment of opportunistic infection in HIV-positive individuals (Pneumocystis pneumonia section), NHS Right Decisions Antimicrobial Prescribing, 2024 update, https://www.rightdecisions.scot.nhs.uk/antimicrobial-prescribing-nhs-grampian-orkney-shetland/hospital-guidance-for-adults/respiratory-system/pneumocystis-jiroveci-carinii-pneumonia/