Alveolitis: Description
Alveolitis is an inflammation of the alveoli of the lungs (pulmonary alveoli). An adult lung has about 400 million such alveoli. Taken together, they form an area of about 100 square meters. Gas exchange between blood (in the vessels around the alveoli) and inhaled air (in the alveoli) takes place over this huge area: Oxygen from the inhaled air is absorbed into the blood through the thin wall of the alveoli, and carbon dioxide is released from the blood into the air.
Often the inflammation of the alveoli – alveolitis – is allergic (exogenous allergic alveolitis, EAA): the affected persons react allergically to inhaled foreign substances. These allergy triggers (allergens) can be, for example, fungal spores, bacterial components, flours, chemicals or animal proteins in excrement (such as bird droppings).
Sometimes the trigger of alveolitis is not an allergy but an infection, a toxin or an immunological systemic disease. However, this text here deals exclusively with exogenous allergic alveolitis.
Exogenous allergic alveolitis: forms
EAA is a relatively rare disease. Depending on the trigger of the allergic alveolitis or the group of people affected, physicians distinguish between different forms of the disease. The most common are avian lung, farmer’s lung and humidifier’s lung:
- Bird farmer’s lung: In this form of EAA, the patient has an allergy to bird droppings and bird proteins from budgies, canaries, pigeons and chickens. Contact with rodent proteins can also trigger EAA in some people.
- Farmer’s lung: Farmer’s lung is the second most common form of exogenous allergic alveolitis. It results from an allergic reaction to inhaled fungal spores from moldy hay.
Other forms of exogenous allergic alveolitis are, for example, sauna visitor lung (triggered by fungal spores on molded wood), detergent lung (triggered by enzyme proteins from detergents), indoor alveolitis (triggered by mold in the house), woodworker lung (triggered by wood dust, mold), steam iron alveolitis (triggered by bacterially contaminated water in the iron), and chemical worker lung (triggered, for example, by isocyanates, released during the production of polyurethane foam). e.g., from isocyanates, released, for example, during the manufacture of polyurethane foam).
Alveolitis: symptoms
The symptoms of acute EAA can easily be confused with those of pneumonia!
The chronic form of EAA develops when someone has repeated contact with smaller amounts of the allergen over months or years (e.g. keepers of pet birds). The persistent inflammation leads to connective tissue-like remodeling processes in the interpulmonary tissue (tissue between the air-carrying sections) as well as a thickening of the alveolar walls (impedes gas exchange!). This is noticeable in the gradual increase in non-specific symptoms – including, above all, increasing shortness of breath (breathlessness) during physical exertion. Other common symptoms are fatigue, lack of appetite, weight loss, slow decline in performance and feeling of illness.
In severe cases of chronic alveolitis, there is progressive scarring of the lung tissue (pulmonary fibrosis).
Alveolitis: Causes and risk factors
Overall, exogenous allergic alveolitis is rare. However, it occurs more frequently in risk groups such as bird breeders or farmers and can lead to occupational disability. Smokers are less likely to develop EAA for reasons that are still unclear.
Alveolitis: examinations and diagnosis
If you have any symptoms of exogenous allergic alveolitis, you should consult a lung specialist or occupational physician. A quick diagnosis is important to be able to initiate treatment quickly and thus prevent long-term damage to the lungs. In an initial consultation, the doctor will first take your medical history (anamnesis). He will ask, for example:
- What exactly are your symptoms?
- How long have they been present?
- What is your profession and since when?
- What are your hobbies?
- Do you have any known lung or skin disease or allergy?
Imaging
In exogenous allergic alveolitis with an acute course, an X-ray of the lungs (chest X-ray) is rather nonspecific. A high-resolution computed tomography (HR-CT) is more informative.
Chronic EAA with the associated connective tissue remodeling processes and scarring in the lung tissue is generally well depicted by imaging, also in X-rays.
Bronchoalveolar lavage
The term “bronchoalveolar lavage” refers to the flushing out of the lower airways (incl. alveoli) performed as part of a bronchoscopy: The physician inserts a so-called bronchoscope – a rigid or flexible tube with an integrated camera – into the airways through the nose or mouth. Through this tube, he then directs irrigation fluid into the lungs (up to the alveoli), which is subsequently aspirated again.
Pulmonary function test
The physician uses a lung function test to determine whether and how severely the lung function is affected by the alveolitis. To do this, the patient must breathe in and out through the mouthpiece of a measuring device. How much air the patient can inhale and exhale in what time and how well the gas exchange (oxygen, carbon dioxide) functions are measured. The results can support the diagnosis of alveolitis.
Other tests
Blood tests can also help diagnose exogenous allergic alveolitis: A targeted search is made in the affected person’s blood for specific antibodies to the suspected allergen. If the detection is successful, this confirms the suspicion.
In unclear cases, a small sample of lung tissue (biopsy) must sometimes be taken and examined under the microscope to confirm the diagnosis.
In addition, a provocation test is best performed under inpatient supervision in specialized centers – allergen contact could cause a severe attack of respiratory distress with oxygen deficiency in the blood.
Analysis of the workplace by a hygiene specialist may also contribute to the diagnosis of exogenous allergic alveolitis, if necessary.
Differentiation from asthma
When making a diagnosis, the physician must distinguish exogenous allergic alveolitis from other diseases with similar symptoms. These so-called differential diagnoses include asthma, in particular allergic asthma. Distinguishing features include:
- Patients with exogenous allergic alveolitis (EAA) usually have no family members with the same disease – unless they are also exposed to the allergen in question (e.g. mold in the shared home). Asthma, on the other hand, often runs in families.
- The symptoms of acute EAA occur a few hours after allergen contact, whereas those of allergic asthma occur immediately afterwards.
- The lungs show constrictions in EAA, whereas in asthma the bronchi show alternating constrictions.
Alveolitis: Treatment
Initially, the patient should avoid any further contact with the allergen, if possible. Those who have bird lung, for example, must remove all birds from the home and also say goodbye to feather beds, pillows and down clothing.
If occupational allergen contact cannot be completely avoided, one can at least try to reduce alveolitis symptoms with suitable preventive measures. These may include wearing a protective mask, installing a good ventilation system, or properly maintaining air conditioning systems. However, such measures are not always sufficient. Patients may then be forced to change jobs or even professions.
Medication
Cortisone can also be helpful in chronic EAA – in higher doses and with prolonged use. In most cases, however, the treating physician prescribes more potent immunosuppressants (e.g., azathioprine, methotrexate) to halt the progression of pulmonary fibrosis. However, the drugs cannot do anything against already existing lung changes and damage.
Lung sports
Rehabilitation measures such as pulmonary exercise are an important therapeutic component for chronic respiratory diseases, including chronic exogenous allergic alveolitis. The targeted physical training can increase performance, reduce respiratory distress and also benefit the psyche. Overall, this improves the quality of life of patients. However, it is important that the amount of exercise is appropriate – neither too much nor too little, is the motto. Patients therefore receive an individually tailored exercise program.
Alveolitis: course of the disease and prognosis
In a chronic course, on the other hand, this alveolitis has a worse prognosis: neither avoidance of the allergen nor medication can reverse the existing scarring (fibrotic) changes in the lung tissue. One can only stop the progression of pulmonary fibrosis – and that is extremely important:
After all, with an increasingly scarred, thickened lung framework, the heart must pump blood from the right ventricle into the pulmonary circulation against greater resistance. The resulting high pressure in the lungs (pulmonary hypertension) can lead to cardiac insufficiency – or more precisely, to right-sided cardiac insufficiency as a result of cor pulmonale (pulmonary heart disease). In most cases, only a lung transplant can help those affected.
