Extrinsic allergic alveolitis in children

Introduction to exogenous allergic alveolitis in children Hypersensitivity pneumonitis (hypersensitivity pneumonitis) is a group of non-asthmatic allergic lung diseases caused by different allergens, with diffuse interstitial inflammation as its pathological feature. It is caused by a hypersensitivity reaction caused by inhalation of various organic dusts, organic dust particles (diameter <10 m) containing fungal spores, bacterial products, animal proteins or insect antigens. Therefore, it is also called extrinsical leriferous alveolitis. In 1932, the peasant's lung was first proposed because of exposure to moldy hay. More recently, immunological techniques have been used more extensively to observe a variety of similar diseases with different antigens and different exposures. basic knowledge The proportion of illness: the probability of illness in infants and young children is 0.0054% Susceptible people: children Mode of infection: non-infectious Complications: serum disease

Causes of exogenous allergic alveolitis in children

(1) Causes of the disease

This disease is an immune disease. The organic dust that causes hypersensitivity lung inflammation has the following types.

1. Thermophilic actinomycetes: from moldy hay, sugar cane, indoor humidifier, air conditioner, etc.

2. Fungi: Such as Aspergillus, Alternaria, etc., derived from barley, wood pulp and the like.

3. Animals: such as birds, rodents, etc., from pigeons, long-tailed parrots, spotted owls, rats, etc.

(two) pathogenesis

Many factors determine the nature of organic dust inhalation, first of all the host's reactivity, allergic individuals have a typical type I allergic reaction to organic dust, while non-atopic individuals cause type III allergic reactions by organic dust, and precipitated antibodies are Specificity changes, the second factor affecting the reaction is the nature and source of the antigen, probably the most important is the size of the dust particles, the largest particles entering the alveoli are 4 ~ 6m, such as most of the particles above 10m, they hang in In the upper respiratory tract, there are not enough small particles to reach and damage the alveoli. The third factor is the exposure to organic dust. The clinical manifestations of severe but intermittent exposure are different from those of less severe long-term exposure. It is generally considered to be type III metamorphosis. The reaction (due to the deposition of immune complexes), but lung biopsy did not find pulmonary vasculitis peculiar to tissue damage of type III allergy, therefore, some people support the view of type IV allergy (slow response) because its histological damage is The acute phase is lymphocytic infiltration of the alveolar wall, followed by monocyte infiltration and scattered non-caseous giant cells Granuloma, late stage is fibrotic tissue and obstructive bronchiolitis, consistent with type IV allergies, but it has also been reported that type II allergic and non-immune mechanisms are involved in the pathogenesis of this disease.

The disease is more common in the inhaled antigen 3 to 6h after the onset of symptoms, 6 ~ 8h peak, disappeared around 24h, such as contact with fungal straw caused by "peasant lungs", allergic to animal protein in bird droppings "Where, it has been reported that there is a certain correlation between the patient's histocompatibility antigen (HLA) system and the occurrence of allergic pneumonia. For example, "the pigeons of the pigeons" occur mostly in white blood cells with HLA-A1.8, suggesting that there is an organization. Compatible antigen systems have associated immune response genes present.

Prevention of exogenous allergic alveolitis in children

The best prevention is to get rid of the allergic environment. The main measure is to get rid of allergens, expose masks to severely exposed people, and treat organic matter with high pressure and high temperature to prevent growth.

Complications of exogenous allergic alveolitis in children Complications

Respiratory, circulatory failure; pulmonary fibrosis and ventilatory insufficiency; systemic vasculitis or serum disease.

Exogenous allergic alveolitis symptoms in children Common symptoms Bunny cell lung fever dry cough dyspnea granuloma

Clinically, symptoms such as fever, dyspnea, dry cough, and discomfort occur immediately after exposure to the antigen. The cause of exogenous allergic alveolitis; can also be caused by repeated or continuous exposure to the antigen, the progressive difficulty in breathing, weight loss, and cyanosis in severe cases. In the acute phase, chest X-ray films are diffuse, small, and blurred with nodular shadows in the middle and lower parts of the chest. They can be absorbed by pathogens or treated with glucocorticoids. The chronic phase is a "honeycomb lung" with multiple interstitial fibrosis in the lungs, accompanied by multiple small cystic transparent areas.

Examination of exogenous allergic alveolitis in children

1. Routine tests: Routine tests have little diagnostic significance. In acute attacks, peripheral blood cells are elevated in white blood cells (15 to 25) × 10 ⁹ /L, with increased neutrophils, but no increase in eosinophils. .

2. Immunological examination: It can be used for the detection of simple Ouchterlony biphasic gel diffusion technique. The specific precipitin IgG of the allergen is found in the serum, which is helpful for diagnosis, but a large number of asymptomatic allergens can also have For the precipitation of specific antigens, gamma globulin can be increased to 20 ~ 30g / L, with IgG, IgM and IgA increased, IgE levels are normal, serum complement is normal, rheumatoid factor can be positive.

3. Chest X-ray: What you see depends on the type of disease. Acute type of alveolar or interstitial pneumonia often infiltrated with diffuse granules. Small knots can also be seen. In chronic cases, infiltration and fusion, X-ray changes It is absorbed after 3 to 6 months, but the severe cases are sustainable.

4. Pulmonary function test: Pulmonary function test shows restrictive ventilatory disorder, dysfunction, including low lung capacity, decreased lung compliance, reduced diffusing capacity, no obvious airway obstruction and increased vascular resistance, local ventilatory blood flow imbalance and arterial blood Oxygen saturation decreases, the latter being more pronounced during exercise.

Diagnosis and diagnosis of exogenous allergic alveolitis in children

According to its non-atopic IgE level is normal, no eosinophilia and bronchospasm, etc., can exclude type I allergic reaction, the first episode of allergic pneumonia is easy to be confused with viral pneumonia, pay attention to identification.

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