Mucormycosis
/ Black Fungus
Mucormycosis, also known as black fungus, is
a serious fungal infection, usually in people with reduced immunity i.e.
ability to fight infections. Symptoms depend on where in the body the infection
occurs. It commonly infects the nose, sinuses, eye and brain resulting in
a runny nose, one sided facial swelling and pain, headache, fever, blurred
vision, swollen and bulging eye, and tissue death. Other forms of disease may
infect the lungs, stomach and intestines, and skin. It is spread by spores of
molds of the order Mucorales, most often through inhalation, contaminated food,
or contamination of open wounds. These fungi are common in soils, decomposing
organic matter (such as rotting fruit and vegetables), and animal manure, but usually do
not affect people. It is not transmitted between people. Risk
factors include diabetes with persistently high blood sugar levels or diabetic ketoacidosis,
low white cells, cancer, organ transplant, iron overload, kidney problems, long-term steroids or
Classification
According to the part of the
body affected, mucormycosis is
classified into five main types. A sixth type has been described
as mucormycosis of the kidney, or
miscellaneous, that is mucormycosis at other sites, although less commonly affected.
v
Sinuses and brain (rhinocerebral); most common in people with poorly controlled
diabetes and in people who have had a kidney transplant.
v
Lungs (pulmonary); the most common type of mucormycosis in people with
cancer and in people who have had an organ transplant or a stem cell
transplant.
v
Stomach and intestine
(gastrointestinal); more common
among young premature and low birth weight infants, who have had antibiotics,
surgery, or medications that lower the body's ability to fight infection.
v
Skin (cutaneous); after a burn, or other skin injury, in people with
leukaemia, poorly controlled diabetes, Graft-versus-host disease, HIV and
intravenous drug use.
v Widespread (disseminated); when the infection spreads to other organs via the blood.
Signs and symptoms
Signs and symptoms of Mucormycosis depend on the
location in the body of the infection. Infection usually begins in
the mouth or nose and enters the central nervous system via the eyes.
v If the fungal infection begins in the nose or
sinus and extends to brain, symptoms and signs may include onesided eye pain or
headache, and may be accompanied by pain in the face, numbness, fever, loss of
smell, a blocked nose or runny nose. The person may appear to have sinusitis. The
face may look swollen on one side, with rapidly progressing "black
lesions" across the nose or upper inside of mouth. One eye may look
swollen and bulging, and vision may be blurred.
v Fever, cough, chest pain, and difficulty
breathing, or coughing up blood, can occur when the lungs are involved.
A stomach ache, nausea, vomiting and bleeding can
occur when the gastrointestinal tract is involved. Affected skin may appear as a
dusky reddish tender patch with a darkening centre due to tissue death.There
may be an ulcer and it can be very painful.
v Invasion into the blood vessels can result in thrombosis and subsequent death of surrounding tissue due to a loss of blood supply. Widespread (disseminated) mucormycosis typically occurs in people who are already sick from other medical conditions, so it can be difficult to know which symptoms are related to mucormycosis. People with disseminated infection in the brain can develop mental status changes or coma.
Cause
Mucormycosis is a fungal infection caused by fungi
in the order Mucorales.]
In most cases it is due to an
invasion of the genera Rhizopus and
Mucor, common bread molds.[28] Most fatal
infections are caused by Rhizopus oryzae. It
is less likely due to Lichtheimia,
and rarely due to Apophysomyces.Others
include Cunninghamella, Mortierella,
and Saksenaea.
The fungal spores are in the environment, can be
found on for instance moldy bread and fruit and are breathed in frequently, but
cause disease only in some people. In addition to being breathed in to be
deposited in the nose, sinuses and lungs, the spores can also enter the skin
via blood or directly through a cut or open wound, or grow in the intestine if
eaten. Once deposited, the fungus grows branch-like filaments which
invade blood vessels, causing clots to form and surrounding tissues to die. Other
reported causes include contaminated wound dressings.[5] Mucormycosis
has been reported following the use of elastoplast and the use of tongue
depressors for holding in place intravenous catheters, Outbreaks have also been
linked to
hospital bed sheets, negative-pressure rooms, water leaks, poor
ventilation, contaminated medical equipment,
and building works.
Risk factors
Predisposing factors for mucormycosis include
conditions where people are less able to fight infection, have a low neutrophil
count or metabolic acidosis. Risk factors include poorly controlled diabetes
mellitus (particularly DKA), organ transplant, iron overload, cancers such as
lymphomas, kidney failure, long term corticosteroid and immunosuppressive
therapy, liver disease and severe malnutrition. Other risk factors include
tuberculosis (TB), deferoxamine and to a lesser extent
HIV/AIDS. Cases of mucormycosis in fit and healthy people is rare.
Corticosteroids are commonly
used in the treatment of COVID-19 and reduce damage caused by the body's own
immune system during a coronavirus infection.
They are immunosuppressant and increase blood sugar levels in both diabetics and non-diabetic patients. It is thought that both these effects may contribute to cases of mucormycosis.
Mechanism
Most people are frequently exposed to Mucorales
without developing the disease. Mucormycosis is generally spread by breathing
in, eating food contaminated by, or getting spores of molds of the Mucorales
type in an open wound. It is not transmitted between people.
The precise mechanism by which diabetics become susceptible is unclear. In vivo, a high sugar alone does not permit the growth of the fungus, but acidosis alone does. People with high sugars -frequently have higher iron levels, also known to be a risk factor for developing mucormycosis. In people on deferoxamine, the iron removed is captured by siderophores on Rhizopus species, which uses the iron to grow.
Diagnosis
There is no blood test that can confirm the
diagnosis. Diagnosis requires identifying the mold in the affected tissue by
biopsy and confirming it with a fungal culture. Because the causative fungi
occur all
around, a culture alone is not decisive.[5] Tests may also include culture and direct detection of the fungus in lung fluid, blood, serum, plasma and urine. Blood tests include a complete blood count to look specifically for neutropenia. Other blood tests include iron levels, blood glucose, bicarbonate, and electrolytes. Endoscopic examination of the nasal passages may be needed.
Imaging
Imaging is often performed, such as CT scan of
lungs and sinuses. Signs on chest CT scans, such as nodules,
cavities, halo signs, pleural effusion and wedge-shaped shadows, showing
invasion of blood vessels may suggest a fungal infection, but does not confirm
mucormycosis. A reverse halo sign in a person with a
blood cancer and low neutrophil count, is highly suggestive of mucormycosis. CT scan images of mucormycosis can be useful to distinguish mucormycosis of the orbit and cellulitis of the orbit, but imagingmay look identical to those of aspergillosis. MRI may also be useful.
Culture and biopsy
To confirm the diagnosis, biopsy samples can be cultured. Culture from biopsy samples does not always give a result as the organism is very fragile. To precisely identify the species requires an expert. The appearance of the fungus under the microscope will determine the genus and species.[35] The appearances can vary but generally show wide, ribbon-like filaments that generally don't have septa and that unlike in aspergillosis, branch at right angles, resembling antlers of a moose, which may be seen to be invading blood vessels.
Prevention
Preventive measures include wearing a face mask in dusty areas, washing hands, avoiding direct contact with water-damaged buildings, and protecting skin, feet, and hands where there is exposure to soil or manure such as gardening or certain outdoor work.[10] In high risk groups such as organ transplant, antifungal drugs may be given as a preventative.
Treatment
Treatment involves a combination of antifungal drugs, surgically removing infecting tissue and correcting underlying medical problems such as diabetic ketoacidosis.
Medication
Once mucormycosis is suspected, Amphotericin B at an initial dose of 1mg is initially given slowly over 10-15 minutes into a vein, then given as a once daily dose according to body weight for the next 14 days. It may need to be continued for longer. Isavuconazole and Posaconazole are alternatives.
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