With more cases of mucormycosis being reported and linked to COVID-19 recovered patients, Dr Anchal Gupta, senior eye surgeon, Netram Eye Foundation analyses the information about this opportunistic fungal infection most often seen in immunosuppressed recovered individuals
Mucormycosis, also known as Black Fungus, is a ferocious opportunistic fungal infection. Mucormycosis can affect other parts of the body such as the lungs, gastrointestinal tract, open skin wound. This article discusses the rhino-orbito-cerebral type.
The fungus is omnipresent in nature and is found in soil and on decaying vegetation. Humans are exposed to it on a daily basis, the fungal spores are inhaled through the mouth and nose. A healthy adult with intact immune system goes unaffected, whereas in an immunocompromised individual germination and hyphae formation occur and infection develops, most commonly in the sinuses and lungs.
The infection starts from the paranasal sinus mucosa, spreads to the orbital apex and, from there, gain intra cerebral access. Mucormycosis is difficult to diagnose early and is a rapidly progressive infection. By the time signs of orbital apex involvement develop, it is often too late to save the patient’s vision, or even the patient’s eye or life. The presentation is typically a rapidly progressive infection, and the disease is associated with a high mortality rate.
The onset may be associated with non-specific symptoms such as nasal congestion, postnasal drip, dark blood-tinged or purulent rhinorrhoea, sinus tenderness, headache, fever, malaise. There can be external signs of one-sided swelling on cheeks, periorbital swelling, redness in eye, diplopia, ophthalmoplegia, ptosis, sharp pain in eye and subsequent blurring or loss of vision. A black necrotic eschar on the nasal turbinates or hard palate is characteristic of maxillary sinus involvement. As the fungus invades further the orbital apex is involved.
The occurrence of mental status changes, hemiparesis, or seizures suggests intracranial invasion. The time from onset of initial symptoms to late symptoms and signs that are diagnostic of the disease may be as short as one day to three days. The development of late symptoms and signs indicates a poor prognosis.
The disease is classically seen in immunosuppressed individuals. COVID-19 recovered patients who were hospitalised for prolonged high flow oxygen therapy and received high doses of steroids with pre-existing immunosuppressive conditions like uncontrolled diabetes mellitus, persons who have received multiple blood transfusions, severe neutropenia, renal failure, transplants, hematopoietic malignancies, or any other cancer or those on chronic steroids or immunosuppressants.
With sinus involvement, RI may demonstrate variable T1 and T2 intensity with focal lack of enhancement in areas of devitalised sinus mucosa. With involvement of the cavernous sinus, CT scans may show lack of enhancement in this region, which is consistent with thrombosis by the invasive fungus. Other radiographic findings of mucormycosis include a rim of soft tissue thickness along the paranasal sinuses, opacification of the sinuses, fluid levels in the sinuses, and bone destruction.
Direct histologic examination of scrapings or biopsies of involved tissue or paranasal sinus secretions are diagnostic. Biopsy may need to be repeated if initial biopsies are negative.
Optimal medical therapy relies on rapid correction of underlying systemic abnormalities, such as neutropenia and hyperglycaemia, along with prompt antifungal initiation and aggressive surgical intervention.
Lipid-based amphotericin B, which destroys the cell wall of the fungus, is the first-line medical treatment for mucormycosis and should be initiated as soon as the diagnosis is suspected. High doses are required, and nephrotoxicity may result; however, liposomal formulations may deliver high doses while protecting renal function.
Early aggressive surgical debridement is important for successful management of invasive fungal disease. This can be done endoscopically or through an open approach. The surgeon should debride until normal, well-perfused; bleeding tissue is encountered. Daily repeat debridement may be needed until clinical improvement is established. With extensive spread of the disease, orbital exenteration, along with removal of the sinuses, may be necessary.
Before the advent of amphotericin B, mortality rates associated with mucormycosis were as high as 90 per cent. The disease continues to have high mortality rates, with one study reporting a range of 50 to 80 per cent.