Aspergillosis

Definition

Definition of Aspergillosis
Aspergillosis is the name given to a wide variety of diseases caused by fungi of the genus Aspergillus. The most common forms are allergic bronchopulmonary aspergillosis, pulmonary aspergilloma and invasive aspergillosis. Most humans inhale Aspergillus spores every day. Aspergillosis develops mainly in individuals who are immunocompromised, either from disease or from immunosuppressive drugs, and is a leading cause of death in acute leukemia and hematopoietic stem cell transplantation. Conversely, it may also develop as an allergic response. The most common cause is Aspergillus fumigatus.

Symptoms

Symptoms of Aspergillosis
A fungus ball in the lungs may cause no symptoms and may be discovered only with a chest X-ray, or it may cause repeated coughing up of blood and occasionally severe, even fatal, bleeding. A rapidly invasive Aspergillus infection in the lungs often causes cough, fever, chest pain, and difficulty breathing.

Aspergillosis affecting the deeper tissues makes a person very ill. Symptoms include fever, chills, shock, delirium, and blood clots. The person may develop kidney failure, liver failure (causing jaundice), and breathing difficulties. Death can occur quickly.

Aspergillosis of the ear canal causes itching and occasionally pain. Fluid draining overnight from the ear may leave a stain on the pillow. Aspergillosis of the sinuses causes a feeling of congestion and sometimes pain or discharge.

In addition to the symptoms, an X-ray or computerised tomography (CT) scan of the infected area provides clues for making the diagnosis. Whenever possible, a doctor sends a sample of infected material to a laboratory to confirm identification of the fungus.

Causes

Causes of Aspergillosis
Aspergillosis is caused by a fungus (Aspergillus), which is commonly found growing on dead leaves, stored grain, compost piles, or in other decaying vegetation. It can also be found on marijuana leaves.

Although most people are often exposed to aspergillus, infections caused by the fungus rarely occur in people who have a normal immune system. The rare infections caused by aspergillus include pneumonia and fungus ball (aspergilloma).

There are several forms of aspergillosis:

1. Pulmonary aspergillosis - allergic bronchopulmonary type is an allergic reaction to the fungus that usually develops in people who already have lung problems (such as asthma or cystic fibrosis).
2. Aspergilloma is a growth (fungus ball) that develops in an area of past lung disease or lung scarring (such as tuberculosis or lung abscess).
3. Pulmonary aspergillosis - invasive type is a serious infection with pneumonia that can spread to other parts of the body. This infection almost always occurs in people with a weakened immune system due to cancer, AIDS, leukemia, an organ transplant, chemotherapy, or other conditions or medications that lower the number of normal white blood cells or weaken the immune system.

Diagnosis

Diagnosis of Aspergillosis
On chest X-ray and CT, pulmonary aspergillosis classically manifests as a halo sign, and, later, an air crescent sign. In hematologic patients with invasive aspergillosis, the galactomannan test can make the diagnosis in a noninvasive way.

On microscopy, Aspergillus species are reliably demonstrated by silver stains, e.g., Gridley stain or Gomori methenamine-silver. These give the fungal walls a gray-black colour. The hyphae of Aspergillus species range in diameter from 2.5 to 4.5 µm. They have septate hyphae, but these are not always apparent, and in such cases they may be mistaken for Zygomycota. Aspergillus hyphae tend to have dichotomous branching that is progressive and primarily at acute angles of about 45°.

Treatment

Treatment of Aspergillosis
The current treatments include voriconazole and liposomal amphotericin B. Newer findings suggest use of mild oral steroids for a longer period of time, preferably for 6-9 months in aspergillosis in pulmonary segment.

Other drugs used, such as amphotericin B, caspofungin (in combination therapy only), flucytosine (in combination therapy only) or itraconazole, are used to treat this fungal infection. However, a growing proportion of infections are resistant to the triconazoles.

Prognosis

Prognosis of Aspergillosis
With treatment, people with allergic aspergillosis usually get better over time. It is common for the disease to come back (relapse) and need repeat treatment.

If invasive aspergillosis does not get better with drug treatment, it eventually leads to death. What happens to a person with invasive aspergillosis also depends on their disease and immune system function.

Prevention

Prevention of Aspergillosis
Be careful when using medications that suppress the immune system. Preventing AIDS also prevents certain diseases, including aspergillosis, that are associated with a damaged or weakened immune system.