Alveolitis Exogenous Allergic

Hypersensitivity pneumonitis, inhalation pneumopathy, “poultry farmer’s lung”, “farmer’s lung”, etc. is a pathological process in the lungs that occurs in response to a known causative factor - an allergen (organic or inorganic dust, fungi, bacteria, etc.) and is expressed by hyperergic reaction. Both the antigenic structure of the causative factors and the characteristics of the response of the macroorganism are important.

Pathogenesis
Hydrolytic enzymes of alveolar macrophages cause the breakdown of complement with the formation of C3 fractions and subsequently lead to the formation of the C3b component, which through alternative pathways leads to a greater intensity of C3 breakdown. Activation of the production of immunoglobulins by B lymphocytes leads to the formation of immune complexes, which are subsequently deposited on the basement membrane of the pulmonary vessels and, when complement is fixed on their surface, become available for absorption by phagocytes. The lysosomal enzymes released in this case have a damaging effect on the pulmonary parenchyma according to the Arthus phenomenon.

Clinical picture
The clinical picture is varied and depends on the degree of antigenicity of the causative allergen, the massiveness and duration of the antigenic effect, and the characteristics of the macroorganism. These factors determine the course of the disease (acute, subacute, chronic).

Main signs: rise in body temperature, chills, shortness of breath, cough (usually dry), weakness, pain in the chest, muscles, joints, headache. Difficulty breathing and vasomotor rhinitis are possible. Small- and medium-bubbling, dry wheezing rales are detected.

When you stop contact with the causative allergen, these symptoms disappear after 12-48 hours. Repeated contact with the causative factor leads to an exacerbation of the process.

Long-term and repeated exposure to small doses of antigen contribute to the development of a fibrosing process in the lungs: progressive shortness of breath, cyanosis, weight loss, and in advanced cases, pulmonary hypertension with right ventricular hypertrophy occurs.

Diagnosis
The diagnosis is based on the clinical picture, leukocytosis with a shift of the leukocyte formula to the left, increased ESR, moderate eosinophilia, identification of specific precipitating antibodies (IgG class, positive Ouchterlonu test) and immune complexes, results of provocative inhalation tests, x-ray examination.

Differential diagnosis is carried out with alveolitis of infectious origin.

Treatment
Avoid contact with the causative allergen. Prednisolone at the rate of 1-1.5 mg per 1 kg of child’s body weight per day for 2 weeks, followed by a gradual reduction in the dose. In case of chronic course with the development of diffuse pneumofibrosis - cuprenil.

Forecast
In acute cases it is favorable, in subacute and chronic cases it is serious.