Exogenous allergic alveolitis: diagnosis

Laboratory data

General analysis of blood - changes depend on the clinical form of the disease, the activity of the process.

The acute form of exogenous allergic alveolitis is characterized by leukocytosis, a shift of the leukocyte formula to the left, a moderate eosinophilia (non-permanent sign), an increase in ESR. In exogenous allergic alveolitis caused by aspergillas, there may be significant eosinophilia.

Similar changes in the hemogram are observed in the subacute form of the disease, but may be less pronounced.

In the chronic form of exogenous allergic alveolitis, symptomatic erythrocytosis can develop and hemoglobin levels rise (with progressive respiratory failure), the number of leukocytes and ESR may increase during the period of exacerbation of the disease, in the remission phase, the number of leukocytes may remain normal.

Biochemical analysis of blood - with pronounced activity of the disease (especially in acute and subacute forms), an increase in the content of gamma globulins, seromucoid, haptoglobin, sialic acids is observed.

General analysis of urine - without significant changes.

Immunological studies - it is possible to reduce the subpopulation of T-lymphocytes-suppressors, positive reactions of blast transformation of lymphocytes (RBTL) and inhibition of migration of leukocytes with a specific antigen are observed, and the detection of circulating immune complexes is possible.

Also specific antibodies of the IgG class are detected by the Ouchterlony precipitation reaction, passive hemagglutination, oncoming immunoelectrophoresis, immunoenzyme method, laser nephelometry. However, it should be noted that specific antibodies to the antigen are not always found in the blood and their absence does not contradict the diagnosis of exogenous allergic alveolitis in the presence of other characteristic signs of the disease.

Often, a test of degranulation of basophils and leukolysis in the presence of the allergen that causes the disease is positive.

Investigation of fluid obtained during lavage of the bronchi - in the period of exacerbation of the disease there is an increase in the number of neutrophils and lymphocytes, a decrease in the number of T-lymphocytes-suppressors; As the process fades, the number of T-lymphocytes-suppressors increases. Characteristically, an increase in the content of IgA, G, M

Instrumental research

Radiography of the lungs

The acute form of exogenous allergic alveolitis is manifested by widespread interstitial changes in the lungs in the form of netting, vagueness of the vascular contour, possible infiltrative changes with fuzzy contours located in the lower parts of both lungs and subpleural.

In the subacute form of exogenous allergic alveolitis, bilateral fine-focal dimming 0.2-0.3 cm in diameter is detected (reflection of the granulomatous process in the lungs). After the termination of the effect of the etiologic factor, these changes in the lungs gradually disappear within 1-2 months. With continued contact with the allergen, already expressed signs of interstitial fibrosis appear in the sub-stage of the stage.

In the chronic form of exogenous allergic alveolitis, characteristic signs of severe pulmonary fibrosis are revealed: widespread cellular deformation of the lung pattern, diffuse mesh and linear shadows, a picture of the "cellular lung", signs of wrinkling of the lung, pulmonary hypertension.

Examination of respiratory function

In the acute phase of exogenous allergic alveolitis, a decrease in the ZHEL is detected and there is a moderate violation of bronchial patency (due to the development of bronchioloalveolitis). Similar changes are also registered in the subacute phase of the disease. In the chronic form of exogenous allergic alveolitis, a restrictive type of respiratory failure is formed, characterized by a sharp decrease in GEL.

Investigation of blood gas composition

Disorders of blood gas composition are observed mainly in patients with chronic form of exogenous allergic alveolitis as interstitial fibrosis progresses and development of severe respiratory failure. At this stage of the disease, the diffusion capacity of the lungs is sharply disrupted, arterial gstoxemia develops.

ECG. It is possible to detect deviations of the electric axis of the heart to the right, with severe clinical manifestations and a prolonged course of exogenous allergic alveolitis, ECG signs of myocardial hypertrophy of the right atrium and right ventricle appear.

Lung biopsy

Transbronchial and open lung biopsies are used. When developing a chronic form of exogenous allergic alveolitis, an open biopsy is used, since percutaneous biopsy is of little informative value. The main morphological signs of exogenous allergic alveolitis in lung biopsies are:

• lymphocytic infiltration of alveoli and interalveolar septa;
• presence of granulomas (are not determined in chronic forms of the disease);
• signs of obliteration of the alveoli;
• interstitial fibrosis with deformation of bronchioles;
• sections of pulmonary emphysema, fragmentation and decrease in the number of elastic fibers;
• detection of immune complexes in the walls of the alveoli (using the immunofluorescence method of biopsy examination).

Diagnostic criteria for exogenous allergic alveolitis

The diagnosis of exogenous allergic alveolitis can be made on the basis of the following provisions:

• the presence of a connection between the development of the disease and a certain etiologic factor;
• the disappearance in most cases of symptoms of the disease or a significant decrease after the cessation of contact with the allergen;
• positive results of provocative inhalation tests in natural (industrial) conditions. The patient is examined before starting work, then in the middle and at the end of the working day. The following parameters are evaluated: respiratory rate, body temperature, LIV, general health of the patient. Usually, before the work starts, these indicators are at the lower limit of the norm or are lowered, the patient's condition is satisfactory. In the middle and, especially, at the end of the working day, all indicators and the general condition of the patient undergo a very
  pronounced negative dynamics due to the influence of the production etiologic factors during the day. The test is highly specific and not accompanied by complications. There is also a kind of acute inhalation test. The patient is encouraged to inhale the aerosol containing the suspected antigens and evaluate the above indices. If the patient has exogenous allergic alveolitis, these indicators and the patient's state of health deteriorate sharply. It should be noted that these diagnostic tests are most informative in acute and subacute exogenous allergic alveolitis and are much less informative in chronic forms;
• positive intradermal tests with an allergen, which presumably causes exogenous allergic alveolitis;
• detection of specific precipitating antibodies in the blood;
• bilateral widespread crepitus, more pronounced above the basal parts of the lungs;
• X-ray picture of pulmonary dissemination of nodular character or diffuse interstitial changes and "cellular" lung;
• restrictive type of ventilation disorders in functional examination of the lungs in the absence or minor violations of bronchial patency;
• detection of specific stimulation of lymphocytes in RBTL (blastic transformation of lymphocytes) or RTML (the inhibition of migration of leukocytes);
• characteristic morphological manifestations in lung biopsy specimens.

Differential diagnosis

Differential diagnosis of exogenous allergic alveolitis should be performed with other forms of fibrosing alveolitis, primarily with idiopathic fibrosing alveolitis.

Often it is necessary to differentiate exogenous allergic alveolitis with bronchial asthma. In contrast to exogenous allergic alveolitis, bronchial asthma is characterized by:

• attacks of suffocation, during which a large number of dry whistling and buzzing rales are heard;
• disappearance of dry wheezing in an interictal period;
• obstructive type of pulmonary ventilation disorders;
• high levels of IgE in the blood of patients;
• the definition of sputum eosinophils, Charcot-Leiden crystals, Kurshman spirals in sputum.

When differential diagnosis of exogenous allergic alveolitis with chronic obstructive bronchitis should be noted that, in contrast to exogenous allergic alveolitis for chronic obstructive bronchitis is characterized by:

• long-term smoking for many years;
• scattered dry wheezing and buzzing rales at auscultation of the lungs;
• obstructive type of pulmonary ventilation dysfunction;
• a suppurative cough with separation of mucopurulent sputum;
• the positive effect of treatment with bronchodilator-anticholinergics (ipratropium bromide), stimulants of beta2-adrenoreceptors.

Survey program

1. General tests of blood and urine.
2. Biochemical blood test: determination of total protein and protein fractions, haptoglobin, seromucoid, aminotransferases, bilirubin, creatinine, urea.
3. Immunological studies: determination of T- and B-lymphocytes, T-lymphocyte subpopulations, immunoglobulins, circulating immune complexes, RBTL and RTML with the presumed allergen, the etiologic factor of the disease.
4. Provocative inhalation test in production conditions or acute inhalation test.
5. ECG.
6. Radiography of the lungs.
7. Spirography.
8. Determination of the gas composition of blood.
9. Investigation of bronchial lavage fluid: determination of the cellular composition of T- and B-lymphocytes, subpopulations of T-lymphocytes, immunoglobulins.
10. Open lung biopsy.

Examples of the formulation of the diagnosis

1. Exogenous allergic alveolitis ("farmer's lung"), acute form.
2. Exogenous allergic alveolitis ("lung of a poultryman"), a chronic form. Chronic non-obstructive bronchitis. Respiratory failure II st. Chronic compensated pulmonary heart.

[1], [2], [3], [4], [5]