Microbiology · Mycobacterial and Fungal Diagnostics (NAAT, LPA, Culture, DST, IGRA, Galactomannan)

An immunocompromised patient on prolonged high-dose corticosteroids develops fever unresponsive to antibiotics and a new pulmonary infiltrate. Bronchoalveolar lavage (BAL) galactomannan index is 2.8. What is the most likely diagnosis and the recommended first-line treatment?

  • A Pneumocystis jirovecii pneumonia (PCP); IV co-trimoxazole
  • B Pulmonary mucormycosis; liposomal amphotericin B
  • C Candida pneumonia; IV fluconazole
  • D Invasive pulmonary aspergillosis (IPA); voriconazole IV/oral
Correct answer: D. Invasive pulmonary aspergillosis (IPA); voriconazole IV/oral

Explanation

A BAL galactomannan (GM) index ≥1.0 is diagnostic for invasive pulmonary aspergillosis (IPA) per EORTC/MSG revised criteria. Galactomannan is a polysaccharide component of the Aspergillus cell wall released during hyphal growth; BAL GM has superior sensitivity (90%) over serum GM for IPA. Voriconazole IV or oral is the first-line treatment for IPA (superior to amphotericin B in a landmark RCT). Isavuconazole is a non-inferior alternative. Mucormycosis does NOT produce galactomannan (hence negative GM is used to distinguish mucormycosis from aspergillosis). PCP is diagnosed by silver stain/IFT on BAL.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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