A 58-year-old man with poorly controlled diabetes mellitus (HbA1c 11.2%) presents with a 5-day history of facial swelling, black necrotic eschar on the hard palate, and fever (38.9°C). He reports rhinosinusitis symptoms and blurred vision in the left eye. On examination, there is proptosis and ophthalmoplegia. Blood glucose is 380 mg/dL, and serum pH is 7.28. A biopsy of the palatal lesion shows broad, non-septate hyphae with right-angle branching. What is the most likely diagnosis?

Explanation

## Clinical Presentation & Key Features **Key Point:** The constellation of poorly controlled diabetes, black necrotic palatal eschar, rhinosinusitis, proptosis, ophthalmoplegia, and broad non-septate hyphae with right-angle branching is pathognomonic for rhinocerebral mucormycosis. ## Organism Identification | Feature | Mucormycosis | Aspergillosis | |---------|--------------|---------------| | **Hyphae morphology** | Broad (6–16 μm), non-septate | Narrow (3–4 μm), septate | | **Branching angle** | Right angles (90°) | Acute angles (45°) | | **Angioinvasion** | Marked; causes tissue necrosis | Present but less aggressive | | **Black eschar** | Characteristic (necrotic tissue) | Rare | | **Risk factor** | Uncontrolled diabetes, acidosis | Neutropenia, hematologic malignancy | ## Pathophysiology 1. **Spore inhalation** → colonization of nasal mucosa and paranasal sinuses 2. **Angioinvasion** → vascular thrombosis and tissue necrosis 3. **Rapid spread** → palate, orbit, brain via vascular invasion 4. **Black eschar** = necrotic tissue from ischemia (hallmark finding) **Clinical Pearl:** Diabetic ketoacidosis (DKA) or uncontrolled hyperglycemia with acidosis dramatically increases risk. The organism thrives in acidotic, hyperglycemic states; Mucor is ketone-utilizing. **High-Yield:** Proptosis + ophthalmoplegia + black palatal eschar = mucormycosis until proven otherwise. This is a medical emergency requiring immediate ENT/neurosurgery consultation and aggressive surgical debridement + IV liposomal amphotericin B. ## Why Broad Non-Septate Hyphae Matter **Key Point:** Non-septate hyphae with right-angle branching are diagnostic for Mucorales (Rhizopus, Mucor, Rhizomucor). Aspergillus has septate hyphae with acute-angle branching — a critical morphologic distinction. ## Management Implications - **Urgent:** Aggressive surgical debridement of necrotic tissue (may require multiple procedures) - **Medical:** IV liposomal amphotericin B (5 mg/kg/day) — conventional amphotericin B is less effective - **Glycemic control:** Insulin to normalize glucose and resolve acidosis - **Prognosis:** High mortality (30–90%) if CNS involvement; early diagnosis and surgery improve outcomes [cite:Robbins 10e Ch 8]