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Exogenous allergic alveolitis (synonym: hypersensitive pneumonitis, interstitial granulomatous alveolitis) is a group of diseases caused by intensive and, more rarely, prolonged inhalation of antigens of organic and inorganic dusts and are characterized by diffuse, in contrast to pulmonary eosinophilia, lesions of the alveolar and interstitial structures of the lungs. The emergence of this group of diseases is associated with the development of immunocomplex (type III) and cell-mediated (type IV) allergic reactions.

Atonic IgE-dependent mechanisms are not characteristic of allergic alveolitis. The inflammatory process is localized in the alveoli and interstitium of the lungs, and not in the airways, as in bronchial asthma, although the latter can be a concomitant disease in patients with alveolitis.

Etiological factors that can cause exogenous allergic alveolitis can be divided into 3 groups:

1) microorganisms (bacteria, fungi, protozoa and their metabolic products (proteins, enzymes, endotoxins, etc.));

2) organic matter of animal and vegetable origin (animal hair, feather of birds, rice dust, etc.);

3) low molecular weight compounds (diisocyanite, salts of heavy metals, including gold), medical preparations (intal, antibiotics, nitrofurans, antimycotic drugs, antimetabolites). For the occurrence of alveolitis, several conditions are necessary:

1) inhalation route of antigen penetration (diameter of dust particles no more than 5 microns);

2) high concentrations of antigen in the inhaled air and significant exposure;

3) the antigen should be presented in a corpuscular form (cells) or in the form of an aggregated protein; soluble antigens do not cause the development of alveolitis;

4) the antigen must have the ability to activate the complement system in an alternative way, i.e. without antibodies.

Pathomorphologically allergic alveolitis is characterized by damage to the alveolar and endothelial cells, vasculitis, mononuclear, and / or polynuclear infiltration of the interstitial tissue and alveolar structures of the lungs, the formation of sarcoid-like granulomas, interstitial fibrosis.

The name of the disease most often reflects an etiological factor:

“Lung of flour mills”, “lung of cheese makers”, “lung of poultry farmers”, etc.

During the disease, acute, subacute and chronic stages (forms) are distinguished.

The acute form develops 4-12 hours after the patient contacts the allergen. There is a flu-like syndrome: chills, fever, cough, shortness of breath, nausea, myalgia, arthralgia. Other acute forms are pneumonia-like (crepitus and wet rales during auscultation, interstitial infiltrates during radiography) and bronchotic (dry cough, "diffuse wheezing in the lungs) syndromes.
Neutrophilic leukocytosis is observed in the blood. When examining the function of external respiration, a mixed type of respiratory failure (obstructive and restrictive) is revealed. Radiologically, reticular or modular (diameter 0.1-1 cm) infiltrative shadows can be detected:

changes in the type of "frosted glass", indistinguishability of the vascular pattern.

The acute form may have a progressive course with severe

prognosis, however, more often, suspension due to illness from work or hospitalization leads to an improvement in the condition. The diagnosis of an acute form of exogenous alveolitis is rare, usually diagnosed with influenza, acute respiratory viral infections, acute pneumonia or bronchitis.

The subacute form develops with continued contact with the antigen. In these cases, the “Monday phenomenon” is typical:

acute manifestations are observed in the days after rest, and subside by the end of the working week.

The chronic form of exogenous allergic alveolitis is observed with long-term contact with the allergen and the long course of the disease. Pathologically, this form is based on interstitial fibrosis ("fibrosing alveolitis"), so the clinical manifestations of the disease are similar to the clinic of idiopathic fibrosing alveolitis (Hammen-Rich disease). Patients with respiratory failure progressing, accompanied by asthenic syndrome, anorexia, weight loss. Pulmonary heart develops with appropriate symptoms. An X-ray examination reveals signs of pulmonary fibrosis: diffuse mesh, modular and linear shadows, symptoms of freezing of the lung, picture of the “cell lung”. In the study of HPF, a restrictive type of respiratory failure is recorded.

DIAGNOSTICS of exogenous allergic alveolitis is carried out on the basis of an assessment of the clinic of the disease, a thorough history, instrumental methods and immunological examination. For - identification of specific antibodies, precipitation reactions, passive hemagglutination, and enzyme immunoassay are used. Diagnostic significance is given to the pagopental reaction of blast transformation of lymphocytes and inhibition of leukocyte migration with a specific antigen.

Intracutaneous tests with a dilution of allergen 1:10 have not lost their significance. Sometimes a lung biopsy is required.

The differential diagnosis is carried out in the acute stage with acute respiratory viral infections, influenza, acute pneumonia, acute bronchitis. In the chronic stage, the disease is differentiated from idiopathic fibrosing alveolitis and granulomatous processes in the lungs (tuberculosis, sarcoidosis, Wegener's granulomatosis, etc.) -
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