What is aspergillosis?
Aspergillosis is disease caused by aspergillus.
What is aspergillus?
Aspergillus is a fungus (mould) that is found in abundance throughout the environment in soil, decomposing plant matter, ornamental plants, water, household dust, and building materials. More than 100 different species of aspergillus have been identified, but the species most commonly implicated in human disease are A. fumigatus, A. flavus, and A. niger.
Who gets aspergillosis?
Aspergillosis is more frequently diagnosed when conditions producing impaired immunity become more prevalent. For example, invasive aspergillosis is estimated to occur in 5–13% of recipients of bone marrow transplants, in 5–25% of patients who have received heart or lung transplants, and in 10–20% of patients who are receiving intensive chemotherapy for leukaemia.
The term aspergillosis is not used to refer to chronic nail infections caused by aspergillus, which is a form of onychomycosis that affects people with normal immune systems.
How does aspergillosis occur?
Aspergillus most commonly enters the human body via inhalation. Most people breathe in aspergillus spores every day, with no ill-effect. However, in patients with pre-existing medical conditions, aspergillus can start to proliferate and cause disease, primarily a lung infection. Infection is more likely if a large number of spores are inhaled, such as on exposure to a very dusty environment or during renovation of a building.
On rare occasions, the fungus may enter via the skin (primary cutaneous aspergillosis), particularly in patients with thermal burns or trauma. Occasionally, outbreaks of primary cutaneous aspergillosis is due to contaminated biomedical equipment.
Aspergillus can also spread to the skin via the blood stream.
What are the clinical features of aspergillosis?
There are four common clinical patterns of disease.
Acute invasive aspergillosis
- Acute invasive apsergillus has a rapid onset and the disease progresses quickly.
- The fungus invades and damages body tissues; most commonly the lungs and/or sinuses, but can spread throughout the body via the bloodstream.
- Symptoms include fever, cough, breathlessness, chest pain, facial swelling, bleeding nose, bulging of an eye, or neurological symptoms. Other symptoms develop if the infection spreads beyond the lungs and sinuses.
- There is a high fatality rate.
Acute invasive apsergillus affects people with severely impaired immunity, particularly those:
- who have had a bone marrow transplant or solid organ transplant
- on high doses of corticosteroids or chemotherapy for cancers such as leukaemia
- with advanced HIV infection.
- Allergic aspergillosis is an allergic reaction to the aspergillus fungus in the lungs and/or in the sinuses.
- Lung symptoms include fever, wheezing, and coughing. Patients may cough up blood or mucous plugs.
- Sinus symptoms include facial pressure, headache, blocked nose, yellow or green discharge from the nose, and cough.
Allergic aspergillosis can affect anyone, but is more common in people with asthma or cystic fibrosis.
- Aspergilloma is a “fungus ball” that develops in a pre-existing lung cavity.
- It may cause no symptoms or the patient may cough up blood (which can be profuse and life-threatening).
- Aspergillomas can also develop in other organs.
Aspergilloma affects people with an underlying cavity-causing lung disease, such as tuberculosis, emphysema, or cystic fibrosis.
Chronic necrotising pulmonary aspergillosis
- Chronic necrotising pulmonary aspergillosis is a rare condition that causes tissue death within the lungs.
- This form of aspergillosis slowly progresses over weeks or months.
- Symptoms often include fever, cough, night sweats, and weight loss.
- Chronic necrotising pulmonary aspergillosis usually affects people with mild immune impairment, such as underlying lung disease, alcoholism, or who are on long-term corticosteroid therapy.
What are the skin manifestations of aspergillosis?
Skin changes are most commonly a consequence of widespread infection with aspergillus in patients with impaired immunity.
- Around 5–10% of patients with invasive aspergillosis develop skin lesions.
- Lesions include single or multiple red or violet hardened plaques or papules. The lesions may be tender or symptom-free. As the lesions evolve, pus- or blood-filled blisters develop in the centre, which eventually become necrotic blackened ulcers or scabs. Lesions most commonly appear on the limbs and head, and may affect a small or large area.
Primary cutaneous aspergillosis most commonly develops at the site of an intravenous cannula insertion or venipuncture (wound from a blood test).
- Occlusive dressings may increase the risk of developing primary cutaneous aspergillosis.
- Localised immunosuppression due to intralesional steroid injection can be associated with cutaneous aspergillosis.
- Lesions initially appear similar to cellulitis, then develop into a necrotic ulcer or scab.
How is aspergillosis diagnosed?
- Samples of sputum, blood, or affected tissue can be cultured in the laboratory to grow aspergillus.
- The fungus may be visible under a microscope in biopsies of affected tissue. Special stains for fungus may be needed, but other fungi may appear nearly identical.
- Chest x-ray or CT scan of the lungs can reveal characteristic abnormalities.
- A newer antigen-based test is available to detect evidence of invasive aspergillosis in the blood. However, the accuracy of this test appears to be variable.
Aspergillus in the laboratory
How is aspergillosis treated?
- Voriconazole is currently used as first-line treatment for invasive aspergillosis.
- Other drugs used to treat aspergillosis include itraconazole, amphotericin B, caspofungin, micafungin, and posaconazole.
- Prolonged treatment is usually required.
- When possible, immunosuppressive therapy, such as systemic corticosteroids, should be discontinued.
- Surgical removal of the infected lung cavity may be required in the case of an aspergilloma.
Can aspergillosis be prevented?
Because the aspergillus fungus is present everywhere throughout the environment, it is virtually impossible to avoid it altogether. In patients with severely impaired immunity, the following measures may be helpful:
- Avoid dusty environments, construction sites, gardening, and lawn mowing
- Wear protective face masks when near dusty environments
- Take preventative antifungal medication if recommended by your physician.
- Use a high-efficiency particulate air filter (HEPA) in hospital to prevent hospital-acquired lung infection in patients with poor immunity.