Question: Multisystem Processes & Disorders
A 65-year-old man with diabetic ketoacidosis develops fever and proptosis of the left eye over 3 days. He is unable to move the left eye fully. Examination shows a black, necrotic eschar on the nasal mucosa. A biopsy of the affected tissue is most likely to show which of the following organisms?
Choose one answer.
Explanation
Correct answer: A. Broad, ribbon-like hyphae with wide-angle branching
Rhinocerebral mucormycosis occurs in poorly controlled diabetics, particularly during ketoacidosis, and presents with facial pain, proptosis, cranial nerve involvement, and a black necrotic eschar from angioinvasion. The causative Mucorales fungi show broad, nonseptate, ribbon-like hyphae that branch at wide (roughly 90-degree) angles. Acute-angle septate hyphae describe Aspergillus, the thick capsule describes Cryptococcus, pseudohyphae describe Candida, and spherules describe Coccidioides.
Learning objective: Match rhinocerebral mucormycosis in DKA to broad nonseptate hyphae.
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