Question

A poorly controlled diabetic patient presents with facial pain and a black eschar over the nasal/palatal region. Which organism is most likely responsible?

• A. Rhizopus species (mucormycosis)
• B. Aspergillus species
• C. Candida species
• D. Cryptococcus neoformans

Hint:

Diabetic ketoacidosis + black eschar = mucormycosis (broad aseptate hyphae).

Answer 1

The Correct Option is A

Step 1: Recognise the classic clinical picture.
A diabetic (especially in ketoacidosis) with rapidly progressing facial pain and a black necrotic eschar on the palate or nose is the textbook presentation of rhino-orbito-cerebral mucormycosis.

Step 2: Identify the fungus.
Mucormycosis is caused by the order Mucorales - chiefly Rhizopus (also Mucor, Rhizomucor, Lichtheimia). On microscopy these show broad, aseptate (or sparsely septate) ribbon-like hyphae branching at wide (~90 deg ) angles. They are angioinvasive, causing thrombosis and the characteristic black eschar from tissue necrosis.

Step 3: Why diabetics?
Hyperglycaemia and acidosis impair neutrophil function and increase free iron availability; Rhizopus also has a ketone reductase that lets it thrive in the acidotic, glucose-rich milieu.

Step 4: Eliminate the distractors.
Aspergillus has narrow septate hyphae branching at acute (~45 deg ) angles and typically causes invasive disease in neutropenic/immunosuppressed hosts - not the diabetic black-eschar picture. Candida causes mucocutaneous/invasive candidiasis, not an invasive facial eschar. Cryptococcus causes meningitis in HIV/immunosuppressed patients.

Key fact: Diabetic + black palatal/nasal eschar = mucormycosis, classically due to Rhizopus.