A 58-year-old man with poorly controlled diabetes mellitus (HbA1c 11.2%) presents with a 5-day history of fever, facial swelling, and black necrotic eschar on the hard palate. On examination, he has proptosis of the right eye and ophthalmoplegia. Blood glucose is 380 mg/dL, and arterial blood gas shows pH 7.28 with bicarbonate 12 mEq/L. Nasal endoscopy reveals black necrotic tissue. Histopathology shows broad, non-septate hyphae with right-angle branching. What is the most likely diagnosis?

Explanation

## Diagnosis: Mucormycosis with Rhinocerebral Involvement ### Clinical Presentation This case presents the classic triad of rhinocerebral mucormycosis: 1. **Black necrotic eschar on hard palate** — pathognomonic sign of tissue necrosis due to angioinvasion 2. **Proptosis and ophthalmoplegia** — indicates orbital/cavernous sinus involvement 3. **Poorly controlled diabetes with ketoacidosis** — the most common predisposing factor (accounts for ~50% of mucormycosis cases) ### Histopathological Findings **Key Point:** The broad, non-septate hyphae with right-angle branching are diagnostic of Mucorales. This is in stark contrast to Aspergillus, which has septate hyphae with acute-angle (45°) branching. ### Pathophysiology **High-Yield:** Mucormycosis is angioinvasive — the organism directly invades blood vessel walls, causing: - Thrombosis and tissue infarction (leading to black necrotic tissue) - Rapid progression to CNS involvement - High mortality if not treated emergently ### Comparison: Aspergillus vs. Mucor | Feature | Aspergillus | Mucor | | --- | --- | --- | | Septation | Septate | Non-septate | | Branching angle | Acute (45°) | Right angle (90°) | | Angioinvasion | Rare | Common | | Tissue necrosis | Uncommon | Characteristic | | Risk factors | Neutropenia, hematologic malignancy | Diabetes (especially DKA), hematologic malignancy | | Palatal involvement | Rare | Common in rhinocerebral form | ### Clinical Pearl **Black eschar = Mucor until proven otherwise.** The presence of tissue necrosis is the clinical hallmark that distinguishes mucormycosis from other fungal infections. ### Management Implications 1. **Urgent ENT and neurosurgery consultation** for tissue debridement 2. **IV Amphotericin B** (liposomal formulation preferred) — start immediately 3. **Aggressive glycemic control** — essential to reduce mortality 4. **Repeat debridement** may be necessary as infection progresses **Warning:** Delay in diagnosis is the primary cause of mortality in mucormycosis. Any diabetic patient with facial swelling and black necrotic tissue requires immediate investigation.