Exogenous allergic alveolitis: causes, symptoms, treatment, prognosis

What is exogenous allergic alveolitis?

Exogenous allergic alveolitis is a group of diseases caused by contact with various organic molecules and chemical compounds that, when inhaled, cause an allergic reaction. The reaction is the result of repeated exposure to particles of different sizes, called antigens, that enter the lungs during respiration.

Antigens can be organic (e.g. bacteria, fungi, animal excrement, feathers) or inorganic - chemical compounds used in food and woodworking industry. Their adverse effects are exacerbated by environmental conditions such as moldy hay or grain; humidifiers, contaminated air conditioning systems, paint shops, metalworking shops and smelters, polyurethanes in aerosols.

Impaired immune response to antigens causes alveolitis.

The disease can be acute, develop several hours after exposure, or chronic. Chronic forms develop latently for months, sometimes years. This division into forms is questioned by some scientists who believe that exogenous allergic alveolitis is a chronic disease with exacerbations of varying severity in individual patients.

Signs and symptoms

Allergic alveolitis has two forms - acute and chronic. Symptoms of acute allergic alveolitis mimic an acute respiratory infection. These include:

• dyspnea;
• heat;
• chills;
• malaise;
• joint pain;
• cough.

Symptoms appear within hours of exposure to antigen. In some patients, symptoms regress spontaneously, although they may return after another exposure to the antigen. In rare cases, symptoms can be so severe that they cause respiratory distress.

In chronic form allergic alveolitis symptoms are minor and may go unnoticed during long time. These include:

• intermittent cough with expectoration;
• progressive deterioration in exercise tolerance, i.e. feeling of slight fatigue during exertion;
• low temperature;
• weight loss.

Sometimes appear cyanosis of the lips, pallor of the skin, perspiration as an expression of respiratory distress, especially during exercise.

What if there are symptoms of allergic alveolitis?

If you notice symptoms of exogenous allergic alveolitis, you should consult your general practitioner. It should be remembered that cough and shortness of breath can be symptoms of many other medical conditions. In acute conditions, when severe shortness of breath occurs, an ambulance should be called.

Causes and risk factors

Allergic alveolitis is usually caused by repeated exposure to animal or plant dust, but not exclusively, in an occupational setting. To get into the tiny sacs of the lung, where oxygen is exchanged with the blood, this dust must be less than a certain size, described as 5 microns. (A micron is one millionth of a meter, and therefore about one twenty-five thousandth of an inch.)

Many different substances can be associated with this disorder that may be encountered in the professional environment, including irritants associated with poultry (bird down, feathers), cheese production (mold), sugar production (moldy sugarcane pollen), agriculture (moldy hay dust), laboratory work (rat urine residues), tobacco (snuff), heating and cooling systems (moldy water), malting / brewing (moldy barley), plastics processing (plastic residue), epoxy (heated epoxy residue), enzymatic detergent, paints and etc.

Affected populations

Allergic alveolitis is a rare disease. One person in 100 thousand gets sick. once a year. Both children and adult men and women are ill. The disease develops in only about 1.6% of people exposed to a specific antigen in high concentrations.

Diagnostics

First of all, the doctor collects information about the current history of diseases, medications taken, concomitant diseases, as well as the effects of substances that can cause allergic alveolitis - both at work and in home conditions. Adequate questionnaires are available to determine antigen exposure. The specialist then examines the patient.

In the future, the doctor can order additional tests, as a rule, these are laboratory blood tests: blood smear, CRP protein, general analysis, the presence of so-called precipitating antibodies in the serum. In addition, the doctor may order imaging tests such as lung x-rays or computed tomography chest, as well as functional tests such as spirometry, plethysmography, assessment of the ability to diffuse gases. Sometimes it is necessary to do broncho-fibroscopy and an assessment of the follicular fluid or even a lung biopsy, i.e. take tissue material and conduct histopathological evaluation.

Related disorders

Symptoms of the following disorders may mimic exogenous allergic alveolitis. Comparisons can be useful for differential diagnosis:

• Asthma characterized by shortness of breath caused by a variety of factors, often associated with allergies. In general, air passages narrow and may spontaneously return to normal, although treatment is often necessary. The severity of chronic cases may decrease, depending on the underlying cause and treatment. There is no known cure, but attacks can be controlled to varying degrees.
• Desquamative interstitial pneumonia is a chronic form pneumonia. The exact cause of the disorder is not known. Symptoms are caused by secretion of large alveolar cells (desquamation) in the lungs and thickening of the airways. This disorder is characterized by shortness of breath and accompanied by a violent cough that does not seem to relieve the obstruction.
• Fibrosing alveolitis, also known as Hamman-Rich syndrome, is an inflammatory lung disease characterized by abnormal formation of fibrous tissue between tiny air sacs (alveoli) or ducts in the lungs. Coughing and rapid breathing can develop even with moderate exercise. The skin can become bluish (cyanotic) due to a lack of oxygen circulating in the blood. Complications such as infections, emphysema or heart problems.
• Granulomatous pneumonitis Is a rare lung disease characterized by inflamed nodules in the lungs. Inhalation of various antigens, such as bacteria (even dead bacteria) or fragments of microbial cells, can overstimulate the immune system in the lungs, leading to symptoms of the disease. An antigen is a substance, usually a protein or carbohydrate, that can stimulate an immune response. As for granulomatous pneumonitis, the syndrome triggers an immune response. Symptoms include complications in the lungs, dry cough, and shortness of breath. This respiratory problem is often misdiagnosed as pulmonary tuberculosis or any other lung disease.
• Sarcoidosis of the lungs - a disease that affects many systems of the body. It is characterized by small, round lesions (tubercles) in the tissue. Symptoms can vary depending on the severity of the disease and the proportion of the affected organism. Widespread lung involvement can occur with or after lymph node involvement. Lung involvement is usually characterized by coughing and shortness of breath, although these symptoms may be mild or absent.

Treatment

The main treatment procedure is the absolute cessation of antigen exposure, i.e. interruption of contact with birds in case of reactions to bird allergens (down, feathers), changing the workplace, etc.

The acute form of allergic alveolitis sometimes disappears without treatment when the intensity of symptoms is low. Sometimes glucocorticoids are given for several weeks if severe symptoms occur.

In chronic forms, glucocorticosteroids are administered over many weeks, gradually decreasing the dose. Treatment may be ineffective due to the chronic, progressive nature of the lung lesions - chronic inflammation leads to type changes pulmonary fibrosis. Changes are often progressive despite cessation of exposure, resulting in respiratory failure of varying severity. There remains only symptomatic treatment of respiratory failure - oxygen therapy, antitussive therapy, symptomatic treatment of shortness of breath. Individual cases are eligible for lung transplantation.

In acute forms and exacerbation of chronic forms, hospitalization in the intensive care unit is sometimes necessary.

Is it possible to completely cure exogenous allergic alveolitis?

Rapid recognition of acute forms after complete destruction of the pathogen ensures complete recovery. The chronic form of the disease is long-term, and its course varies from person to person.

Forecast

The prognosis is good if the disease and exposure to the pathogen are detected at an early stage. Therefore, further exposure to the pathogen can be avoided. However, established lung scarring will not resolve, and these patients may progress inexorably to lung failure.

The overall result is excellent when the majority of patients recover completely after the antigen exposure has ceased.