This page explains the effect that aspergillus, a species of fungus, or mould, has on the lung.
What is aspergillus and how does it affect the lung?
Aspergillus and asthma
Allergic bronchopulmonary aspergillosis (ABPA)
Allergic alveolitis – ‘malt worker’s lung’
Aspergilloma (fungus ball)
Invasive aspergillosis
Aspergillus is a species of fungus (mould). Several different types occur widely in the environment. They invade and colonise vegetable matter, especially when wet and/or rotting. The organisms grow to produce tiny filaments, or fibres, known as mycelia, and they reproduce by making tiny spores.
In certain environments, such as barns where farm produce is stored, airborne spores may be very numerous indeed. This means they are breathed in via the lung airways (bronchi) to the gas exchanging tissue in the lungs – the alveoli.
Not all inhaled spores reach the alveoli. Some get stuck on the lining (mucosa) of the nose and the eyes, while some are caught in the mucus made by bronchial cells. Most of these spores are removed or destroyed by the body’s defensive mechanisms. Occasionally, the body reacts to them with an exaggerated immune response, thereby causing allergy.
Alternatively, the body’s immune response may not be very good and aspergillus grows and causes infection. Occasionally, aspergillus grows to form a ‘fungus ball’ in the holes of damaged segments of lung.
The potential to affect the lungs in such different ways means that there is a wide range of diseases caused by aspergillus. On the one hand, aspergillus may cause no more than a mild irritation in the nose but, on the other hand, it is very occasionally life threatening.
In people with asthma the bronchial tubes become irritable, inflamed and are likely to narrow abnormally. This makes it harder to get air in and out of the lungs. Asthma attacks are often triggered by common allergies (such as pollens, house dust mite, animal hairs) but also by a type of aspergillus called ‘A. Fumigatus’.
Periods of wheezing, chest tightness, breathlessness and cough may be triggered by exposure to fungal spores in people who have inherited a tendency to develop allergies and who are more able to produce antibodies (proteins used by the body to fight viruses or bacteria) to common environmental substances. These people are often called ‘atopic’. The diagnosis is made by looking at the history of exposure and confirmed by detecting evidence of certain antibodies, called ‘IgE’ antibodies, specific to A. Fumigatus, from either blood or skin prick tests.
Management of asthma attacks involves avoiding exposure to A. Fumigatus and taking conventional treatment for asthma.
This condition is a complication of sensitisation to aspergillus, usually A. Fumigatus, in people with known allergic asthma, cystic fibrosis or bronchiectasis. It occurs in 8-10 per cent of people with cystic fibrosis, 1-2 per cent of people with asthma and 7-14 per cent of people with severe asthma who require long-term steroid treatment. Symptoms are usually worsening asthma, fever, general malaise and cough. The symptoms may come and go or they may gradually get worse. When phlegm (sputum) is coughed up, it contains characteristic, brownish rubbery lumps (plugs or parts of plugs which block the lung airways) and sometimes blood. When these lumps are examined under a microscope, the fibres (mycelia) are visible, indicating that aspergillus has been growing in the airways. The condition may be associated with chronic sinusitis.
A chest X-ray will show the characteristic flitting shadows which represent pneumonia-like inflammation, consisting predominantly of eosinophils (special blood cells which are associated with allergic reactions). These flitting shadows may sometimes occur even if there are no new symptoms. The chest X-ray may also show areas of collapsed lung, where mucus has blocked off bronchial tubes and the air beyond has been reabsorbed. Abnormally high numbers of eosinophils are found in the blood along with ‘IgE’ and ‘IgG’ antibodies.
Treatment with steroids often dramatically improves symptoms within hours to days and such a reaction to steroid treatment can be used to confirm the diagnosis. Additional antifungal treatment (such as itraconazole) is sometimes useful.
When treatment is successful, breathing improves, the plugs of sputum blocking the bronchial tubes are coughed up and the chest X-ray clears. As this is an allergic condition, antibiotics are of no benefit. However, if steroids are gradually withdrawn, the condition usually recurs and so generally a long-term, relatively high dose steroid is required.
The mucus plugging of airways may occasionally damage airways permanently, called bronchiectasis. More commonly repeated attacks of ABPA can result in pulmonary fibrosis – permanent scarring in the gas-exchanging alveoli. Bronchiectasis will usually result in a long-term cough, producing sputum, while pulmonary fibrosis produces long-term breathlessness. Steroid treatment is less effective once pulmonary fibrosis is present.
Another type of aspergillus, A. clavatus, may contaminate barley during the malting stage of whisky production. People inhaling spores from malt or moulding hay may develop an allergic reaction called allergic alveolitis (or hypersensitivity pneumonitis) in the gas-exchanging part of the lung (alveoli). This is very rare.
Within hours of exposure to the spores a flu-like illness develops with fever, aches and pains, malaise and loss of appetite, accompanied by a dry cough and breathlessness. The symptoms gradually improve within hours to a few days of not being exposed to the spores, only to recur with any further exposure.
The diagnosis is usually made from the history of exposure and is confirmed by finding a specific (IgG) antibody to A. clavatus in the blood. Further episodes of illness can usually be prevented by avoiding exposure to A. clavatus. However, this is not always realistic (especially in family-run farms and whisky distilleries) and so there is a place for the use of protective respirators (masks, for example) during the course of particular tasks that cause exposure. Very occasionally, if exposure has been particularly heavy, admission to hospital and steroid treatment may be necessary. Rarely, with continuing exposure and recurrent episodes, progressive diffuse pulmonary fibrosis (scarring of the lung) develops.
A number of lung diseases – particularly tuberculosis (TB), certain pneumonias causing lung abscesses, sarcoidosis, and pulmonary fibrosis – may leave a hole (cavity) inside the lung when they heal. This cavity is made of scar tissue with little blood supply. This means that the normal body mechanisms preventing the killing and reproduction of the inhaled aspergillus are relatively inactive. This allows the fungus to gather and live. Eventually, a fungus ball (aspergilloma) is formed within the cavity; about 17 per cent of old TB cavities are complicated by aspergillomas.
Sometimes, aspergillomas cause no symptoms but are only discovered by chance on a chest X-ray. However, in about three-quarters of cases the main symptom is coughing up blood. Occasionally (in 5-10 per cent of patients), this is so severe that it is life-threatening. The diagnosis is made by seeing a solid mass inside a cavity on the chest X-ray or CT scan, with a characteristic crescent of air visible around the mass. Usually, aspergillus precipitins (antibodies) are found in the blood.
Often the condition is not troublesome or progressive; it is then best to leave it well alone, especially if there are no symptoms. However, if coughing up blood is troublesome, then the cavity and mass can be removed through surgery. However, this can be tricky and the surgery carries a 5-10 per cent chance of death. Other treatments include:
- using surgery to clot the artery causing the bleeding;
- long-term antifungal medication (itraconazole) which can help up to 60 per cent of people; and
- putting another antifungal medication (amphotericin) directly into the cavity via a tube.
Although the local defence mechanisms of the lung and the wider defence mechanisms of the body are normally able to prevent inhaled aspergillus spores from reproducing and invading tissue in the manner of an infectious disease, there are circumstances when aspergillus infection (invasive aspergillosis) does occur.
This is very rare but occurs when the immune defence system of the body is not functioning properly, either due to an inherited disease or to HIV AIDS. Invasive aspergillosis may also occur in the presence of immuno-suppression, following 5-13 per cent of bone marrow transplants, 5-25 per cent of organ transplantations, and in 10-20 per cent of people who have had intensive courses of chemotherapy for leukaemia.
The lungs and sinuses are most commonly affected, with fever, cough (sometimes producing bloody sputum), breathlessness, pleurisy and sinusitis. A severe fungus pneumonia may occur and the fungus may spread through the blood to other organs. This may result in widespread abscess formation, involving the valves in the heart, the blood vessels, brain, liver, spleen, kidneys, guts, eyes and skin. Diagnosis may be very difficult and outlook is often very poor . Up to 90 per cent of patients die because of this extremely rare problem. The infection is treated with antifungal medications.
Code: IS6 Version: 2.0
Last medically reviewed: June 2011
Due for medical review: June 2013
For references call 020 7688 5555
