An HIV-positive patient with a CD4 count of 120 cells per microlitre presents with progressive dry cough, exertional dyspnoea and fever. Chest radiograph shows bilateral diffuse interstitial infiltrates. Which combination of prophylaxis threshold and confirmatory stain is correct for the suspected pathogen?

• A Prophylaxis below CD4 350, diagnosis by India ink showing capsule
• B Prophylaxis below CD4 200, diagnosis by Gomori methenamine silver showing cysts ✓
• C Prophylaxis below CD4 100, diagnosis by Ziehl-Neelsen showing acid-fast bacilli
• D Prophylaxis below CD4 500, diagnosis by periodic acid-Schiff showing broad-based buds

Explanation

Pneumocystis jirovecii pneumonia occurs when the CD4 count falls below 200 cells per microlitre, and co-trimoxazole is given as prophylaxis at that threshold. Diagnosis rests on demonstrating cysts or trophic forms in respiratory specimens using Gomori methenamine silver or toluidine blue stains, with immunofluorescence increasing sensitivity. India ink detects Cryptococcus, acid-fast staining detects mycobacteria and Nocardia, and broad-based budding describes Blastomyces, so each distractor pairs the wrong organism with the wrong threshold.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.