Makindo Medical Notes

Mucormycosis, often termed "Black Fungus," is an aggressive and life-threatening invasive fungal infection with high mortality. Primarily affecting immunocompromised individuals, especially those with uncontrolled diabetes, recent cases have risen significantly in individuals recovering from COVID-19 in regions like India.

About

• Mucormycosis is an opportunistic infection predominantly seen in immunocompromised patients, especially those with poorly controlled diabetes or diabetic ketoacidosis.
• The infection is due to fungi from the order Mucorales, with mortality rates as high as 50-80% if left untreated.
• Also known as the "Black Fungus" due to the necrotic tissue it causes, mucormycosis is uncommon but devastating, affecting an estimated 1-2 per million people.

Aetiology

• Mucorales fungi possess a strong affinity for blood vessels, leading to thrombosis, infarction, and extensive tissue necrosis.
• Initial infection typically occurs through inhalation of spores that settle in the paranasal sinuses or lungs, especially in vulnerable individuals.
• Rhizopus spp. produce an enzyme, ketone reductase, that helps the fungus thrive in high glucose, acidic environments — conditions commonly found in diabetic patients.
• Iron chelation therapy, particularly with Desferrioxamine, has been associated with increased susceptibility to mucormycosis.

Common Organisms

• Mucormycosis is caused by fungi from the order Mucorales, which are ubiquitous in the environment.
• Most commonly isolated genera include:
  • Myocladus spp.
  • Rhizomucor spp.
  • Mucor spp.
  • Rhizopus spp.

Risk Factors

• COVID-19 infection, especially post-COVID recovery due to weakened immune response.
• Diabetic ketoacidosis and poorly controlled diabetes.
• Haematologic malignancies and malnutrition.
• Solid organ transplants, AIDS, severe burns, or long-term corticosteroid therapy.
• Iron chelation therapy, particularly with Desferrioxamine.

Clinical Presentation

• Rhino-Orbital-Cerebral Mucormycosis: Most common form; spores infect via inhalation, causing sinus pain, headache, nasal congestion, and purulent discharge. May lead to necrosis of palate, proptosis, and even brain invasion, presenting with neurological symptoms.
• Pulmonary Mucormycosis: Inhaled spores cause lung infection, leading to severe necrotic and cavitary lesions, cough, dyspnoea, fever, and haemoptysis.
• Cutaneous Mucormycosis: Arises after trauma, presenting as necrotic lesions that can resemble cellulitis but rapidly progress to blackened, gangrenous tissue.
• Disseminated Mucormycosis: Occurs in immunocompromised patients, spreading from lungs or sinuses to the brain, spleen, liver, or other organs.

Investigations

• Laboratory Tests: FBC, blood glucose, and arterial blood gases to monitor metabolic status.
• Histopathology: Identification of fungi in tissue with culture confirmation to guide treatment.
• Imaging:
  • CXR/HRCT of Lungs: Can reveal consolidation, nodules, or cavitations.
  • MRI of Head: Crucial to assess the extent of rhino-orbital-cerebral disease.

Management

• Urgent Treatment: Immediate combination therapy is critical, involving antifungal medication, surgical debridement, and rigorous control of blood glucose levels.
• Antifungal Therapy: Liposomal Amphotericin B is the drug of choice, with high doses required. Step-down therapy with oral Posaconazole may be used for maintenance.
• Surgical Intervention: Surgical debridement of necrotic tissue, especially in rhino-orbital-cerebral cases, is often necessary to halt progression.
• Supportive Care: Mucormycosis is not contagious and requires isolated care to avoid complications.

Poor Prognostic Factors

• Delay in diagnosis and treatment initiation.
• Use of amphotericin monotherapy without surgical debridement.
• Intracranial extension or extensive necrosis, such as facial gangrene or hemiplegia.

References

• Rhino-Orbital-Cerebral Mucormycosis at Eye Wiki