Farmer's lung

Introduction to farmers' lungs Farmer's lung (FL) is an exogenous allergic (hypersensitivity) alveolitis caused by inhalation of organic dust containing thermophilic actinomycetes. Most of the patients are engaged in agricultural production, so they are called peasant lungs. In addition, there are sugar cane pneumoconiosis, mushroom pneumoconiosis, potato pneumoconiosis, humidifier lung (or air conditioner lung), etc., which can contain a lot of thermophilicity due to their living environment. Actinomycetes occur in this disease, some people have allergic pneumonia (hypersensitivity pneumonitis) classified into such diseases, but allergic pneumonia is more broadly meant and should be distinguished. Foreign reports on farmers' lungs began in 1932, but the cause was unknown. By 1962, Pepys and others found antibodies against the thermophilic actinomycete antigen in the serum of peasant lung patients, and confirmed that the disease was type III. Allergic disease-related diseases. In 1981, there were reports of peasant lung cases confirmed by autopsy. basic knowledge The proportion of sickness: 0.04% - 0.06% (the incidence rate of agricultural workers is about 0.04% - 0.06%) Susceptible people: no special people Mode of infection: non-infectious Complications: Pneumothorax Chronic Pulmonary Heart Disease Respiratory Failure

Pediatric lung cause

Bacterial infection (95%):

The genus Actinomyces is the main pathogen of the disease (including many subtypes). In the world, many species of Pseudomonas aeruginosa are used as standard strains. In addition, common thermophilic actinomycetes, white thermophilic actinomycetes, and green thermophilic bacteria have been found in patients in China. Mold is the most common pathogen, and it has been repeatedly verified by animal experiments that it is also a pathogen of farmers' lungs.

Pathogenesis:

Inhalation of a certain amount of thermophilic actinomycetes is the causative condition of the lungs of farmers, but when working in the same environment, only a small number of people are sick, indicating that the incidence is related to the patient's susceptibility factors, and non-agricultural labor in rural areas. Although the population may inhale a small amount of pathogens, it is generally only found in serum that it is related to precipitin antibodies.

Although the thermophilic actinomycetes are the pathogens of the peasant's lungs, they cannot be propagated at 37 °C, and it is difficult to find or culture the thermophilic actinomycetes in the sputum of the patients. Therefore, allergic reactions caused by spores of inhaled pathogens are generally considered. It is its main pathogenesis. The spores of actinomycetes are a heterogeneous substance to the organism. The macromolecular colloid is antigenic. After inhalation, it can stimulate the body to produce an immune response (such as the production of specific antibodies and sensitized lymphocytes). It becomes a sensitized body, and the clinical manifestations of allergic alveolitis or interstitial pneumonia can be obtained within a few hours after inhaling the same spore. It is known that all types I, II, III and IV allergic reactions can participate in the disease. Occurred, but generally type III (immune complex type) and type IV (late type, cellular immune type) allergic reaction.

When the patient inhales the antigen to the alveoli, it can stimulate the body to produce the corresponding antibody (IgG or IgM). When the same antigen is inhaled again, the antigen-antibody binds to form an immune complex in the lung tissue, and under certain conditions, they can deposit on the blood vessel wall. The basement membrane activates complement C3 and releases anaphylatoxins to form a chemotactic complement component, which causes the cells to release lysosomal enzymes during phagocytosis of the antigen-antibody complex, causing an inflammatory reaction leading to tissue damage. The antigen can also be in the body. Contact with sensitized lymphocytes, producing a series of lymphokines that directly or indirectly damage the tissue. In addition, the thermophilic actinomycetes can directly activate the complement bypass pathway, damage lung tissue, or produce some proteolytic enzymes that cause lungs. The tissue inflammatory response, since it is an inflammatory reaction, may be similar to other inflammations, and some cytokines or mediators are abnormal. For example, it has been reported that interleukin-2, -interferon, and adhesion molecule-1 may be There are few factors related to the lung disease and lymphocytic alveolitis in farmers. At present, there are not many studies on this aspect, which needs further study.

Approximately 10% of peasant lung patients develop bronchial asthma symptoms, indicating involvement with type I allergies.

The peasant lung is characterized by the formation of macrophage granulomas and interstitial fibrosis. This granuloma is limited to the respiratory system and is therefore different from other systemic granuloma.

According to our autopsy, lung biopsy and animal experiments, the spore wall of the thermophilic actinomycetes is a hard-to-dissolve granule that has Brownian motion in the alveoli or adheres to the inner surface of the alveoli with respiratory motion. At this time, the expression of soluble intercellular adhesion molecule-1 (ICAM-1) is increased in the patient's bronchial lavage fluid and serum. These particles are engulfed by alveolar macrophages and filled in the alveolar space by means of respiratory movement and surfactants. The role of the respiratory bronchi from the bronchiole to the terminal bronchioles, cleared by the airway in vitro, the smaller diameter of the adhesion can pass through the alveolar epithelial pinocytosis, forming a dustfilled pinocytotic through the cell Alveolar interstitial damage to alveolar epithelial cells and basement membrane, exposing alveolar septum, causing alveolar septal macrophages, lymphocytes to swim out, contact with thermophilic actinomycetes spores to induce immune response, immune complexes and C3 deposits visible in diseased tissues In the process of activation of the complement sequence by the immune pathway through the classical pathway, a series of biologically active substances are produced to cause lung tissue damage. , or antigen-activated complement bypass and lung macrophages cause lung tissue inflammation, a small number of visible eosinophils, sensitized lymphocytes can release a variety of lymphokines, especially macrophage chemokines and activators, Macrophages accumulate locally, enhance phagocytic activity, release lysosomal enzymes during digestion, damage local lung tissue, release fibrotic factors, promote fibroblast proliferation and collagen increase, and occasionally vasculitis changes.

The acute phase lesions are mainly alveolar septal congestion, edema, more mononuclear macrophages and a small amount of neutrophil infiltration, and can form macrophages or epithelial cell granuloma, distributed in the bronchiole wall, alveolar septum In the alveolar cavity, type II alveolar cell hyperplasia can be seen under electron microscope, and alveolar damage can be repaired. If the acute phase cannot be cured in time, it will be repeatedly exposed to antigen and seizures. If it does not heal, it will turn into a chronic phase. At this time, there is a small lung. Scar scar formation, alveolar septal fibrotic hyperplasia, there may be granulomas, lung elasticity decreased, hard, lung volume significantly reduced, pleural thickening, hilar lymph nodes often chronic inflammation, granuloma is type IV allergic reaction The performance may disappear in the late stage of fibrosis, scarring and interstitial fibrosis is the outcome, alveolar dilatation, fusion, formation of periventricular emphysema, and obstructive ventilatory dysfunction, and the above lesions are destroyed. Alveolar gas-blood barrier structure, resulting in respiratory insufficiency, pulmonary vascular inflammatory lesions and hypoxia can cause increased pulmonary circulation resistance, compensatory fertilizer in the right ventricle Large, forming a pulmonary heart disease.

Farmer lung prevention

Avoiding contact with thermophilic actinomycetes is a fundamental measure. Patients who repeatedly attack the lungs of farmers should switch occupations and leave the disease environment. If only one or two episodes of the disease have not occurred again, they can still carry out the original work after taking some preventive measures. Preventive work includes:

1 to publicize the prevention and treatment knowledge of the disease to farmers in the affected areas;

2 Forages, grains, etc. should be fully dried and stored in a well-ventilated place with moisture-proof equipment;

3 mechanization, automated operation can reduce the chance of inhaling spores;

4 spraying 1% to 2% of propionic acid in the forage can prevent the grass from becoming moldy, but it is expensive and should not be used for feed;

5 positive pressure airflow protection helmet, etc., if conditions permit, try it out;

6 Those who have symptoms should seek medical treatment in time, follow up and observe, and those who have irreversible lesions should be removed from work to prevent serious complications.

Farmer lung complications Complications, pneumothorax, chronic pulmonary heart disease, respiratory failure

A small number of pneumothorax can be complicated, and chronic pulmonary heart disease can occur in the late stage. Finally, it can die due to respiratory failure.

Pneumothorax (pneumothorax): refers to the gas into the pleural cavity, resulting in a state of accumulation of gas, known as pneumothorax. Usually divided into three categories: spontaneous pneumothorax, traumatic pneumothorax and artificial pneumothorax. Spontaneous pneumothorax is caused by lung disease that ruptures the lung tissue and visceral pleura, or due to the rupture of tiny bubbles and pulmonary bullae near the surface of the lungs, and the air in the lungs and bronchi enters the pleura.

Chronic cor pulmonale, referred to as pulmonary heart disease, is caused by chronic tissue lesions in the lung tissue, pulmonary artery or thoracic cavity, resulting in abnormal lung structure and function, increased pulmonary vascular resistance, increased pulmonary artery pressure, and right heart expansion. , hypertrophy, heart disease with or without right heart failure.

Pediatric lung symptoms Common symptoms Nausea shortness and fatigue, dry cough, loss of appetite, body discomfort, shortness of breath, shortness of breath, fever, fever

Traditionally, farmers' lungs can be divided into acute, subacute and chronic three types. Subacute types are mostly acute delays. They develop and have severe symptoms and are easily misdiagnosed. However, it is difficult to define their time and clinical manifestations, and it is rare. It is generally not necessary to include regular classification.

Acute type: When inhaled a large number of spores of Xenopus actinomycetes within 4 to 8 hours, the onset is rapid, chills, high fever, sweat, general malaise, loss of appetite, nausea, headache, chest tightness, shortness of breath, dry cough or a small amount Mucus sputum, it is easy to be diagnosed as "cold" at this time, but the upper respiratory tract symptoms are not obvious, about 10% of patients may have asthma-like episodes, skin itching and mucosal edema, type I (rapid hairstyle) allergic symptoms, physical examination When you have shortness of breath, or even lack of oxygen, the lower lungs may smell a small amount of wet squeaks and snoring sounds, occasionally screaming, heart rate, etc. After the exposure to the antigen, the above symptoms may disappear within one or several days, and they may heal themselves. Trends, such as re-exposure when exposed to antigen.

Chronic type: Repeated exposure to a large number of antigens, long-term unhealed, clinical cough, cough, difficulty breathing, hypoxia, cyanosis, extremely weak, secondary infection can be fever, sweating, this is easily misdiagnosed as "chronic bronchitis ", physical examination may have signs of pulmonary interstitial fibrosis or two lungs scattered in the wet voice.

Peasant lung examination

Whether or not the sputum can be found or cultured has no significance for clinical diagnosis, because a large amount of antigen inhalation plays an allergic reaction in the human body, and does not multiply at 37 ° C, and a small amount is found in the sputum. Thermophilic actinomycetes are not necessarily pathogenic. It is generally believed that there are anti-thermophilic actinomycetes (or one of them) in the serum, which can be diagnosed in combination with medical history, but antibody-positive can only indicate that it has been infected. Antigens, such as antibodies that are no longer exposed to antigenic serum, can disappear within a few years. For example, long-term repeated exposure to small amounts of antigen can cause long-term presence of antibodies in serum (such as non-agricultural workers living in the lung-endemic areas of farmers). Our experience is to find a circulating immune complex of the thermophilic actinomycete, which is of great significance for diagnosis because the immune complex will disappear within a few months.

In addition, there may be an increase in the total number of white blood cells, an increase in neutrophils, and occasionally eosinophilia in acute attacks.

Excitation test

The onset of 4 to 8 hours after inhalation of the thermophilic actinomycete spores is the basis for diagnosis, but there may be certain risks during the challenge. For example, if the patient inhales the antigen in the natural environment, the disease can be diagnosed.

Skin antigen tests may also cause serious adverse reactions and should not be used routinely.

X-ray chest performance

In the acute phase, there may be no abnormalities on the initial chest radiograph, or only the lung texture is thickened and disordered. It may also have small nodular shadows in the middle third of the lung field, and the edges are unclear, and the diameter is about 1 mm to several millimeters. The disease is aggravated, the density of the lesion is increased, and the edge is clear. The acute type may disappear within a few days or weeks after the antigen is separated from the antigen, and small nodular lesions may remain. In severe cases, there may be large patchy shadows and diffuse distribution. Chronic type can be seen in small lines or reticular nodular shadows. It can also radiate large cords and plaque shadows from the hilum, and the interstitial space such as honeycomb-like translucent area formation and air trapping. Fibrosis, at this time the lesion has been difficult to resolve, the lesions often occur in the upper middle lung field, bilateral symmetry is not necessarily, occasional pleural effusion, hilar lymphadenopathy, calcification, cavities, atelectasis, etc., lung CT examination is easier Slight lesions, such as ground glass, small nodules, line-like shadows or cystic changes, were found, but the price was more expensive and should be carried out when necessary.

Pulmonary function tests

Early lung function changes are not obvious, there may be restrictive ventilation, advanced obstructive ventilatory dysfunction, severe diffuse volume loss, advanced blood gas analysis may be hypoxia, carbon dioxide slightly reduced.

Fiberoptic bronchoscopy

Chronic visible bronchial mucosa is slightly pale, with more foamy secretions, no specificity, microspore may be found in bronchoalveolar lavage fluid or corresponding thermophilic actinomycetes may be cultured. Some people check plasma cells in lavage fluid, hypertrophy Cell and T-lymphocyte subtype CD4/CD8 ratio inverted, but the clinical significance to be clarified, diffuse lesions can be selectively passed through bronchopulmonary biopsy, alveolitis manifestations or foreign body granuloma formation, and even see inhalation Straw fragments, etc., pulmonary fibrosis manifested in the late stage, but the fiberoptic bronchoscopy is small, sometimes it is difficult to find evidence of the cause, and if necessary, open lung biopsy.

Peasant lung diagnosis

diagnosis

Acute lung diagnosis in farmers:

1 The disease is characterized within a few hours after contact with the spores of the thermophilic actinomycetes (but more often it is considered to be a "cold"). If there are typical symptoms and recurrent symptoms (which can be considered as a natural challenge test), it can be diagnosed. Time-assisted inspection;

2 corresponding X-ray chest performance;

3 pulmonary function tests;

4 serum immunological examination specific antibody positive, especially the specific immune complex positive is more diagnostic value.

Chronic patients often suffer from delayed symptoms, and their clinical manifestations are atypical and misdiagnosed during acute attacks. Therefore, serum immunological tests should be performed when necessary, and even lung biopsy should be performed, combined with clinical comprehensive judgment, at this time on the chest radiograph. The change has been difficult to disappear, the lung function is also obvious, and the diagnosis is not too difficult.

Differential diagnosis

Farmers' lungs should be differentiated from the following diseases:

1. There is a lack of upper respiratory symptoms in the acute onset of lungs in peasants, and it is not difficult to judge the history of exposure to antigens several hours ago.

2. Pneumonia General bacterial pneumonia is not difficult to rule out, but should be distinguished from parasitic, drug allergies and allergic pneumonia such as allergic granulomatous vasculitis.

3. Pulmonary tuberculosis Chronic peasant lung disease persists for a long time, which is easy to be mistaken for tuberculosis, but the latter is a chronic process.

4. Chronic bronchitis recurrent chronic peasant lung patients may have chronic cough and cough performance (according to the investigation of 20% of chronic bronchitis patients in rural Jiangnan province, it is chronic peasant lung), especially in the late stage can also be combined with chronic Bronchitis, but combined with antigen exposure history and serum immunological examination can be distinguished.

5. Bronchial asthma As mentioned above, about 10% of the peasants' lungs may develop asthma-like symptoms, but wheezing is mild, and systemic symptoms are more obvious. Combined with medical history, immunological examination and X-ray chest radiographs can be identified.

6. Idiopathic pulmonary interstitial fibrosis in the lungs of the peasant can present pulmonary interstitial fibrosis, but can be distinguished by a combination of medical history and immunological examination or lung biopsy.

Peasant lung disease can be complicated by pulmonary heart disease, but it is different from pulmonary heart disease caused by chronic obstructive pulmonary disease. The lack of emphysema covers the heart area. The pulmonary valve and apical area are particularly loud and can be mistaken for heart valve disease. Ultra-acoustic inspection can be identified.

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