A patient presents with irregular swelling over the foot, multiple discharging sinuses, and black granules. A KOH mount is performed on the discharge. What is the most likely observation?
Show Hint
Mycetoma triad = swelling, sinus tracts and grains. Black grains commonly suggest fungal cause.
Step 1: Understanding the Question:
The clinical triad of swelling, sinuses, and granules (specifically black granules) in the foot is diagnostic of Mycetoma (Madura foot).
Since the granules are black, it points towards Eumycetoma (fungal origin) rather than Actinomycetoma (bacterial origin). Step 2: Detailed Explanation:
Eumycetoma vs. Actinomycetoma:
Black granules: Are almost exclusively found in fungal mycetoma (Eumycetoma). Common agents include \textit{Madurella mycetomatis}.
White/Yellow granules: Can be found in both, but are more characteristic of Actinomycetoma (e.g., \textit{Nocardia}).
Microscopic Findings in KOH:
Since Eumycetoma is caused by true fungi, the KOH mount of the discharge/granule will show fungal elements.
These fungi typically present as thick, septate hyphae (often 2–5 $\mu$m in diameter) with occasional chlamydospores.
Analyzing other options:
Arthrospores (A): Characteristic of Dermatophytes like \textit{Trichophyton} in hair.
Yeast (C): Characteristic of \textit{Candida} or \textit{Cryptococcus}, not mycetoma.
Slender dematiaceous fungi (B): While some agents are dematiaceous, "septate hyphae" is the more standard histological/KOH description for the diagnostic fungal elements in the granule.
Step 3: Final Answer:
In a patient with eumycetoma (black granules), the KOH mount will reveal the presence of fungal septate hyphae.
