Mucormycosis

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Mucormycosis

Definition

Mucormycosis is a rare but often fatal disease caused by certain fungi. It is sometimes called zygomycosis or phycomycosis. Mucormycosis is an opportunistic infection that typically develops in patients with weakened immune systems, diabetes, kidney failure, organ transplants, or chemotherapy for cancer. It may also develop in patients receiving an iron chelating drug called desferrioxamine (Desferal) as treatment for acute iron poisoning.

Description

In the United States, mucormycosis is most likely to develop in the patient's nasal area or in the lungs; however, it may also develop on the skin or in the digestive tract. Gastrointestinal disease usually develops only in severely malnourished patients. Cutaneous mucormycosis is most likely to develop under occlusive surgical dressings. Occlusive dressings are intended to keep air out of incisions or other wounds, but they also trap body heat and moisture.

The incidence of the disease is difficult to evaluate because it is very rare; however, the rate seems to be increasing. One American cancer center reported in 2000 that mucormycosis was found in 0.7% of patients at autopsy and in 20 patients per 100,000 admissions to the center. The most recent mortality statistics from the Centers for Disease Control and Prevention (CDC) indicate that a total of 22 Americans died from mucormycosis in 2001—1 from pulmonary mucormycosis, 5 from rhinocerebral mucormycosis, 2 from disseminated mucormycosis, and 14 from unspecified forms of the disease.

As far as is known, mucormycosis affects members of either sex and all races equally, although the pulmonary form of the disease is somewhat more common in men than in women. Mucormycosis may develop in patients in any age group, including newborns.

Rhinocerebral mucormycosis

Rhinocerebral mucormycosis is an infection of the nose, eyes, and brain. The fungus destroys the tissue of the nasal passages, sinuses, or hard palate, producing a black or pus-filled discharge and visible patches of dying tissue. The patient will typically have fever, pain, and forward bulging of the eyes (proptosis). The fungus then invades the tissues around the eye socket and eventually the brain. At that point the patient may have convulsions or paralysis on one side of the body.

Pulmonary mucormycosis

Most patients with the pulmonary form of the disease are being treated for leukemia. The fungus enters the patient's lungs, where it eventually invades a major blood vessel, causing the patient to cough up blood or hemorrhage into the lungs.

Gastrointestinal mucormycosis

Gastrointestinal mucormycosis has been reported in premature or low-birth-weight infants as well as malnourished adults. It may lead to intestinal perforation and other complications requiring immediate surgery. A Spanish hospital reported in 2004 on an outbreak of gastrointestinal mucormycosis that affected five patients in an ICU over a 14-week period. Two of the patients died. The outbreak was eventually traced to a supply of wooden tongue depressors that had been contaminated by two species of Rhizopus fungi.

Causes and symptoms

Mucormycosis is caused by fungi of several different species, including Mucor, Rhizopus, Absidia, and Rhizomucor. When these organisms gain access to the mucous membranes of the patient's nose or lungs, they multiply rapidly and invade the nearby blood vessels. The fungi destroy soft tissue and bone, as well as the walls of blood vessels.

The early symptoms of rhinocerebral mucormycosis include fever, sinus pain, headache, and cellulitis. As the fungus reaches the eye tissues, the patient develops dilated pupils, drooping eyelids, a bulging eye, and eventually hemorrhage of the blood vessels in the brain—causing convulsions, partial paralysis, and death.

The symptoms of pulmonary mucormycosis include fever and difficulty breathing, with eventual bleeding from the lungs.

The symptoms of gastrointestinal mucormycosis are not unique to the disease, which may complicate diagnosis. Patients typically complain of pressure or pain in the abdomen, nausea, and vomiting.

Diagnosis

Diagnosis is usually based on a combination of the patient's medical history and a visual examination of the nose, throat, and eyes. The doctor will take a tissue sample for biopsy, or a PAS, potassium hydroxide (KOH), or Calcofluor stain in order to make a tentative diagnosis. Confirmation requires a laboratory culture.

Imaging studies are not needed to make the diagnosis. If the patient has mucormycosis, however, magnetic resonance imaging (MRI) and computed tomography scans (CT scans) will usually show the destruction of soft tissue or bone in patients with advanced disease. Chest x rays will sometimes show a cavity in the lung or an area filled with tissue fluid if the patient has pulmonary mucormycosis.

Treatment

Treatment is usually begun without waiting for laboratory reports because of the rapid spread and high mortality rate of the disease. Therapy includes intravenous amphotericin B (Fungizone); surgical removal of infected tissue; and careful monitoring of the disorder or condition that is responsible for the patient's vulnerability. Most patients who survive require a 4-6-week course of treatment.

Follow-up care includes educating patients about the signs of recurrent mucormycosis—particularly facial swelling and a black discharge from the nose—and telling them to see a doctor at once if they notice these symptoms.

Patients who survive rhinocerebral mucormycosis are often left with severe facial disfigurement and usually require plastic surgery to restore their appearance.

Prognosis

The prognosis for recovery from mucormycosis is poor. The mortality rate is 30%-50% of patients with the rhinocerebral form, and even higher for patients with pulmonary mucormycosis. The disease is almost 100% fatal for patients with AIDS.

Prevention

Prevention depends on protecting high-risk patients from contact with sugary foods, decaying plants, moldy bread, manure, and other breeding grounds for fungi. In addition, health care professionals treating hospital inpatients should be careful to change occlusive dressings frequently and check the underlying skin for any signs of possible fungal infection.

KEY TERMS

Amphotericin B— An antibiotic used to treat mucormycosis and other severe fungal infections.

Opportunistic infection— An infection that develops only when a person's immune system is weakened.

Orbit— The bony cavity or socket surrounding the eye.

Zygomycosis— Another term for mucormycosis. The fungi that cause mucormycosis belong to a group called Zygomycetes.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD, editors. "Mucormycosis." Section 13, Chapter 158. In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Eisen, Damon, MD. "Mucormycosis." eMedicine December 10, 2001. 〈http://www.emedicine.com/med/topic1513.htm〉.

Maravi-Poma, E., J. L. Rodriguez-Tudela, J. G. de Jalon, et al. "Outbreak of Gastric Mucormycosis Associated with the Use of Wooden Tongue Depressors in Critically Ill Patients." Intensive Care Medicine 30 (April 2004): 724-728.

Numa, W. A., Jr, P. K. Foster, J. Wachholz, et al. "Cutaneous Mucormycosis of the Head and Neck with Parotid Gland Involvement: First Report of a Case." Ear, Nose, and Throat Journal 83 (April 2004): 282-286.

Siu, K. L., and W. H. Lee. "A Rare Cause of Intestinal Perforation in an Extreme Low Birth Weight Infant—Gastrointestinal Mucormycosis: A Case Report." Journal of Perinatology 24 (May 2004): 319-321.

Wolf, O., Z. Gil, L. Leider-Trejo, et al. "Tracheal Mucormycosis Presented as an Intraluminal Soft Tissue Mass." Head and Neck 26 (June 2004): 541-543.