A 58-year-old male with poorly controlled diabetes mellitus (HbA1c 11.2%) presents with rapidly progressive necrotic lesions of the hard palate and nasal mucosa. Histopathology shows broad, non-septate hyphae with right-angle branching. Which is the most common causative organism of mucormycosis in India?

Explanation

## Most Common Cause of Mucormycosis in India **Key Point:** Rhizopus species accounts for 60–70% of all mucormycosis cases globally and is the predominant cause in India, particularly in the setting of uncontrolled diabetes mellitus. ### Pathognomonic Features of Rhizopus | Feature | Rhizopus | Aspergillus | Candida | Cryptococcus | |---------|----------|-------------|---------|---------------| | **Hyphal morphology** | Broad (6–30 μm), non-septate | Narrow (3–5 μm), septate | Pseudohyphae/yeast | Yeast only | | **Branching angle** | Right angle (90°) | Acute angle (45°) | Variable | N/A | | **Clinical presentation** | Rhinocerebral, cutaneous, pulmonary | Aspergilloma, invasive in immunocompromised | Oral/esophageal thrush, invasive in severe immunosuppression | Meningitis in HIV/AIDS | | **Risk factor** | Uncontrolled diabetes, hematologic malignancy | Hematologic malignancy, prolonged neutropenia | Broad-spectrum antibiotics, central lines | CD4 <50 cells/μL | ### Clinical Context **High-Yield:** The patient's uncontrolled diabetes (HbA1c 11.2%) with acute necrotic palatal lesions is the classic presentation of **rhinocerebral mucormycosis**, the most common form in India. Hyperglycemia impairs neutrophil function and increases angioinvasion risk. **Clinical Pearl:** Mucormycosis is a medical emergency. The broad, non-septate hyphae with right-angle branching are pathognomonic for Mucorales order. Rhizopus is angioinvasive, causing rapid tissue necrosis and potential intracranial extension. ### Why Rhizopus Dominates in India 1. **Epidemiology:** Rhizopus species are ubiquitous in soil and decaying organic matter, with higher environmental prevalence in tropical/subtropical climates. 2. **Host factors:** High prevalence of uncontrolled diabetes in India (especially in rural areas with limited glycemic monitoring) is a major risk factor. 3. **COVID-19 era:** Post-pandemic surge in mucormycosis linked to corticosteroid use in severe COVID-19 patients; Rhizopus remains the leading cause. **Mnemonic:** **RHIZO** = **Right-angle branching, Hyperglycemia (diabetes), Immunocompromised, Zygomycetes order, Omnipresent in soil** [cite:Robbins 10e Ch 8]