Rhino-Orbital-Cerebral Mucormycosis

These infections are virtually confined to individuals with a predisposing illness (e.g. diabetes mellitus). More recently seen with COVID infections in India. Mucormycosis is a very aggressive, life-threatening, invasive fungal infection that has evolved to be one of the most common entities in immunocompromised patients

About

• A fulminant fungal infection seen in patients with uncontrolled diabetes.
• Has also been called the Black fungus. Incidence is 1-2 per million
• Potentially aggressive and fatal fungal infection due to the Mucorales

Aetiology

• Mucor species have remarkable affinity for vascular invasion, and thus they may cause thrombosis, infarction, and extensive necrosis
• Organism gains access to the nervous system via the paranasal sinuses.
• Ubiquitous fungi causing severe soft tissue destruction/infarction
• Starts with inhalation of spores into the paranasal sinuses of a susceptible host.
• Rhizopus spp have an enzyme, ketone reductase. They thrive in high glucose, acidic conditions
• Desferrioxamine enhances pathogenicity of mucormycosis

Organisms

• Fungi belonging to group called Mucoromycotina
• These fungi are typically found in the soil
• Found with decaying organic matter - leaves, compost piles

Classification

• Myocladus spp.
• Rhizomucor spp.
• Mucor spp.
• Rhizopus spp.

Risk factors

• COVID infections, Cancers
• Diabetic ketoacidosis and poorly controlled diabetes
• Haematologic malignancies, Malnutrition
• Severe burns, Steroid treatment, AIDS, Solid organ transplant
• Iron chelation therapy with Desferrioxamine [Desferoxamine]

Clinical

• Rhino-orbital-cerebral disease: spores enter via cuts, scrapes, puncture wounds, or other forms of trauma to the skin. Headache, acute sinusitis with fever, nasal congestion, purulent nasal discharge and sinus pain. Necrosis of palate. Spread to the orbit with proptosis, ophthalmoplegia, and evidence of arterial or retro-orbital venous occlusion Carotid occlusion may follow. Tissues turn black.
• Pulmonary: inhaled fungal spores from environment. Very severe with infarction and necrosis of the lung. Dyspnoea and haemoptysis. Fever, malaise.
• Cutaneous: painful area of necrosis resembling cellulitis
• Disseminated in the immunocompromised

Investigations

• FBC, U&E, Blood glucose, HIV test, Arterial blood gases
• Identify organisms in tissue by histopathology with culture confirmation
• CXR/HRCT Lungs - cavitation, consolidation, nodules and effusions
• MRI head to establish the extent of disease

Management

• Aggressive diagnostic and therapeutic procedures are essential in order to improve the prognosis in these patients.
• Combination therapy including controlling blood sugar, urgent endoscopic sinus or neurosurgical debridement, and antifungal treatment is mandatory to minimize the fatal outcome of this invasive and aggressive disease.
• Mucormycosis is not contagious and does not spread from person to person.
• Surgical resection of necrosed tissue and debridement with the use of amphotericin B.
• The currently favoured approach is high-dose amphotericin B or its liposomal compounds. Oral posaconazole is used as step-down therapy usually for months

Poor prognosis

• Delay in diagnosis and initiation of treatment
• Treatment with amphotericin alone
• Eyelid/facial gangrene
• Intracranial/cerebral invasion
• Hemiplegia

References

• Rhino-Orbital-Cerebral Mucormycosis at Eye Wiki