Pneumonia knowledge - allergic pneumonia

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Allergic pneumonia (hypersensitivity pneumonitis) is a group of non asthmatic allergic lung disease caused by different allergens. Due to in


Allergic pneumonia (hypersensitivity pneumonitis) is a group of non asthmatic allergic lung disease caused by different allergens. Due to inhalation of organic dust particles containing fungal spores, bacterial products, animal or insect protein antigen (the diameter is less than 10) is caused by an allergic reaction, also known as extrinsic allergic alveolitis (extrinsic allergic alveolitis).


Is generally believed that the type of allergic reaction (due to deposition of immune complexes), but not found in biopsy of lung tissue damage, allergic reactions of type specific pulmonary vasculitis, therefore, some people support the type IV allergic reaction (reaction) point of view, because it damages tissue in the acute phase is mainly to the alveolar wall lymphocytic infiltration, then non caseating giant cell granuloma mononuclear cell infiltrate and scattered, the latter is the obstruction of the pulmonary fibrosis and the bronchiolitis, consistent with type IV allergic reaction. But there are reports that the incidence of type II hypersensitivity and non immunological mechanisms are involved in this disease. The disease is more common in inhalation of antigen 3 ~ 6 hours after onset of symptoms, 6 ~ 8 hour, 24 hours away, such as contact with the fungus straw caused by the "farmer's lung", allergic to bird droppings, animal protein "pigeon breeder's lung". It has been reported that there is a correlation between the histocompatibility antigen (HLA) system and the occurrence of the patient. Such as "pigeon lung" occurs in white blood cells with hla-a1, 8, suggesting that there is an association with the histocompatibility antigen system related to the presence of immune response genes.

[pathological changes]

Show subacute granulomatous inflammation with lymphocytes, plasma cells, epithelioid cells and giant cells of Langerhans, resulting in interstitial broadening. After chronic disease, interstitial fibrosis and lung parenchyma destruction occurred, and the capillary bronchus was blocked by collagen and granulation tissue. Continuous contact sensitization antigen may occur after pulmonary fibrosis, severe pulmonary cystic honeycomb.

Clinical manifestation

The first attack is easily confused with viral pneumonia, the symptoms to contact the antigen after hours: fever, cough, chest pain, dyspnea and cyanosis. A few patients with atopic's exposure to antigen after first wheezing and runny nose isokinetic reactions, 4 to 6 hours after a type III reaction performance. A physical examination of pulmonary rales, no wheeze, no real or airway obstruction. Chest X-ray showed diffuse infiltration of interstitial, and miliary or nodular shadows in the lungs, middle and bottom is obvious, later extended to patchy dense shadows.

Acute attack, white blood cells increased peripheral hemogram was 15 * 109 ~ 25 * 109/l (15000 ~ 25000) with increased neutrophils but no eosinophils increased, gamma globulin increased to 20 ~ 30g/l (2 ~ 3g/dl), with IgG, IgM and IgA increased, normal serum complement, rheumatoid factor can be positive. Pulmonary function tests showed that the restrictive ventilation dysfunction had decreased vital capacity, decreased dispersion energy, partial ventilation and blood flow imbalance, no obvious airway obstruction and increased vascular resistance.

Depends on the history (including environmental factors, habits and hobbies), symptoms, signs and pulmonary function changes. The X-ray changes and immunological examination, especially in serum was found to have specific precipitin antigen sensitization, is helpful for the diagnosis of.


Avoid contact with allergens immediately. Such as extensive lung lesion, hormone therapy (prednisone 1 ~ 2mg/ (kg - D), to 1 ~ February) can cause symptoms and signs and X-ray changes quickly disappear.

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