During the second wave in India, a 58-year-old man with poorly controlled diabetes received dexamethasone for moderate COVID-19. Two weeks after discharge he develops facial pain, black necrotic debris over the nasal turbinate, proptosis and visual loss. Histopathology shows broad, aseptate hyphae with right-angle branching. Which organism is the most likely cause?
- A Aspergillus fumigatus
- B Candida albicans
- C Rhizopus arrhizus (oryzae) ✓
- D Cryptococcus neoformans
Correct answer: C. Rhizopus arrhizus (oryzae)
Explanation
Broad ribbon-like aseptate hyphae branching at right angles identify mucormycosis, and Rhizopus arrhizus is the commonest cause, including the large outbreak among post-COVID diabetic patients given corticosteroids. Hyperglycaemia and steroid-induced immunosuppression impair phagocyte function, allowing angioinvasion and infarction. Aspergillus shows septate hyphae with acute-angle branching, while Candida and Cryptococcus appear as yeasts on histology. Management is urgent debridement plus liposomal amphotericin C.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.