Mucormycosis, also known as zygomycosis, is an aggressive, opportunistic fungal infection of the sinuses, skin, gastrointestinal tract, brain or lungs that usually affects individuals who are immunocompromised.
Mucormycosis, first described in 1885, refers to several different diseases that are caused by the fungi in the order of Mucorales. Rhizopus species are usually the cause of mucormycosis. In descending order, the other genera with mucormycosis-causing species include Rhizomucor, Cunninghamella, Apophysomyces, Saksenaea, Absidia, Mucor, Syncephalastrum, Cokeromyces and Mortierella.
Depending on where the fungal spores are deposited, mucormycosis may affect the sinuses, lungs, gastrointestinal tract, brain or skin. Most mucormycosis infections are life threatening. Most patients who have mucormycosis experience severe infections of the facial sinuses, which may extend into the brain. Pulmonary, cutaneous and gastrointestinal infections also occur. Complications may include loss of neurological function, blindness or blood clots in the brain or lung vessels (thrombosis).
Conditions most commonly associated with mucormycosis include diabetes, chronic steroid use, metabolic acidosis, organ transplantation, leukemia/lymphoma, AIDS and treatment with deferoxamine (a chelating agent that removes excess iron from the body).
Diabetic patients are predisposed to mucormycosis because of the decreased ability of their neutrophils to phagocytize (engulf pathogens) and adhere to endothelial walls. In addition, the acidosis and hyperglycemia provide an excellent environment for the fungus to reproduce.
Until the 1950s, mucormycosis was almost always a fatal disease. Researchers estimate that about 25-80% of cases today are fatal, depending on where the infection is. Successful treatment requires correction of the underlying risk factor(s), antifungal therapy (usually with amphotericin B) and aggressive surgery. Permanent residual effects of the disease, such as blindness and cranial nerve damage, occur up to 70% of the time.
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Rhinocerebral mucormycosis: Rhinocerebral mucormycosis is an infection of the sinuses that spreads rapidly to the eye and brain. Rhizopus oryzae account for many cases of rhinocerebral mucormycosis.
Most patients with rhinocerebral disease have diabetes (especially with ketoacidosis) or have malignancies (cancerous tumors) and neutropenia and are receiving broad-spectrum antibiotics like tetracycline (Helidac Therapy®, Sumycin® or Sumycin® Syrup).
Seventy percent of patients diagnosed with rhinocerebral mucormycosis also have diabetes mellitus, although this percentage is declining with the use of chemotherapy and as the frequency of other immunocompromised states become more common. Fewer than four percent of cases occur without a recognized underlying condition. Hyperglycemia (high blood sugar) enhances fungal growth and impairs neutrophil (type of white blood cell that fights against disease and infection) function. Lactic acidosis prevents the white blood cells from performing phagocytosis (engulfing antigens).
Pulmonary mucormycosis: Pulmonary mucormycosis occurs when fungal spores are inhaled into the lungs. It is a rapidly progressive pneumonia that may spread to the chest, heart and brain. Immunocompromised patients, especially those who have malignancies and are neutropenic (low levels of neutrophils, which are the most common white blood cells in the bloodstream) are at an increased risk for developing pulmonary mucormycosis.
Gastrointestinal mucormycosis: Gastrointestinal mucormycosis occurs when the fungus is ingested. Gastrointestinal mucormycosis is most prevalent among individuals who are severely malnourished. The infection may occur throughout the gastrointestinal tract, but it is most likely to affect the stomach, ileum (lower end of the small intestine) and colon.
Cutaneous mucormycosis: Cutaneous mucormycosis occurs when the fungus enters the body through broken skin. Cutaneous mucormycosis causes cellulitis (inflammation of the connective tissue), which eventually results in dead skin and scabs. Patients who have cutaneous mucormycosis may have had prior trauma or have been exposed to contaminated medical equipment, such as bandages. Rare reports of cutaneous mucormycosis have occurred at catheter sites and insulin injection sites.
Central nervous system mucormycosis: Rhinocerebral mucormycosis can potentially spread to the central nervous system, causing central nervous system mucormycosis. Patients with central nervous system mucormycosis often experience headaches, loss of consciousness and focal neurologic symptoms. Patients with this form of mucormycosis may have a history of open head trauma or cancer.