Question

A diabetic patient presents with bloody nasal discharge, orbital swelling and pain. Culture of the periorbital pus shows branching septate hyphae. Which of the following is the most probable organism involved?

• A. Mucor
• B. Candida
• C. Aspergillus
• D. Rhizopus

Hint:

Septate branching hyphae mean Aspergillus; broad aseptate hyphae would mean Mucor or Rhizopus.

Answer 1

The Correct Option is C

Step 1: The clinical picture, a diabetic with bloody nasal discharge, orbital swelling and pain, is a rhino orbital fungal infection. Two main fungal groups cause this, the Mucorales (Mucor and Rhizopus) and Aspergillus.
Step 2: The deciding clue is the microscopy. The pus shows branching SEPTATE hyphae. Hyphal morphology separates the two groups.
Step 3: Aspergillus has septate hyphae that branch at acute angles, classically about 45 degrees, with regular cross walls. So septate hyphae point to Aspergillus.
Step 4: The Mucorales, that is Mucor and Rhizopus, show broad, aseptate or sparsely septate hyphae that branch at wide angles near 90 degrees. They would NOT be described as septate. So Mucor and Rhizopus are excluded by the word septate.
Step 5: Candida is a yeast that forms pseudohyphae and budding cells, not true branching septate hyphae of this filamentous type, so it does not fit.
Conclusion: Branching septate hyphae in this rhino orbital infection indicate Aspergillus, option C. If the hyphae had been broad and aseptate, the answer would have been Mucor or Rhizopus.