An immunocompromised patient develops sinusitis with a black, necrotic eschar over the palate and cheek. CT scan shows bony erosion. KOH preparation of tissue shows broad aseptate hyphae branching at right angles. Which organism is responsible?
- A Aspergillus fumigatus (Invasive aspergillosis)
- B Candida tropicalis (invasive candidiasis)
- C Mucor/Rhizopus species (Mucormycosis) ✓
- D Fusarium species (hyalohyphomycosis)
Explanation
Rhinocerebral mucormycosis is characterised by black necrotic eschar due to angioinvasion and infarction; it occurs in diabetics (especially with DKA) and neutropenic patients. Broad aseptate (coenocytic) hyphae with wide-angle branching (close to 90°) on KOH preparation is the hallmark. Aspergillus shows narrow septate hyphae with acute-angle (45°) dichotomous branching. Treatment for mucormycosis requires liposomal amphotericin B plus surgical debridement. Serum galactomannan is positive in Aspergillus but NOT in mucormycosis — this helps differentiate them.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.