Question
Mucormycosis
Answer
Mucormycosis is a serious, often rapidly progressive and life-threatening fungal infection caused by fungi of the order Mucorales (genera Rhizopus, Mucor, Lichtheimia, and others) — broad, non-septate (or sparsely septate), ribbon-like hyphae that branch at wide (often right) angles, distinguishing them microscopically from the narrower, septate, acute-angle-branching hyphae of Aspergillus.
Predisposing factors: uncontrolled diabetes mellitus, especially with ketoacidosis (a classic and strong association — the acidic, hyperglycaemic, iron-rich environment favours fungal growth and impairs phagocytic function), haematological malignancy/neutropenia, immunosuppressive therapy (including corticosteroids), and, importantly, recent/uncontrolled COVID-19 infection with corticosteroid use and hyperglycaemia (a well-documented risk factor highlighted during the COVID-19 pandemic).
Clinical forms:
- Rhino-orbito-cerebral mucormycosis — the most common and classic form, beginning in the nasal sinuses and spreading rapidly to the orbit and brain, characterized by fungal invasion of blood vessels causing thrombosis and tissue infarction/necrosis (producing the characteristic black, necrotic eschar on the nasal mucosa/palate).
- Pulmonary mucormycosis — in neutropenic/haematological malignancy patients.
- Cutaneous and gastrointestinal forms — less common.
Pathogenesis: the organism shows a marked angioinvasive tendency, invading blood vessel walls, causing thrombosis and consequent tissue infarction/necrosis — this vascular invasion is central to the disease’s rapid, destructive progression and explains the characteristic black necrotic eschar.
Laboratory diagnosis: direct microscopy (KOH mount) of tissue/discharge showing broad, ribbon-like, non-septate hyphae with wide-angle branching; histopathology confirming angioinvasion; culture on Sabouraud dextrose agar (rapid, fluffy, cotton-wool-like growth); imaging (CT/MRI) to assess extent of sinus/orbital/cerebral involvement.
Treatment: aggressive surgical debridement of necrotic tissue combined with systemic amphotericin B (the antifungal of choice); correction of the underlying predisposing condition (glycaemic control, reduction of immunosuppression) is essential alongside antifungal therapy.