小儿外源性变应性肺泡炎

　　一、发病原因

　　本症是一种免疫性疾病，引起超敏感性肺脏炎的有机物尘埃较常见者有以下几类：

　　1、嗜热性放线菌来源于发霉的干草、甘蔗、室内增湿器、空调器等。

　　2、真菌如曲霉菌、链格孢属等，来源于大麦、木纸浆等。

　　3、动物如鸟、啮齿动物等，来源于鸽子，长尾小鹦鹉、斑鸠、鼠等。

　　二、发病机制

　　许多因素决定有机物尘埃吸入的性质，首先是宿主的反应性。变应性个体对有机物尘埃起典型的Ⅰ型变态反应，而非特应性个体则由有机物尘埃引起Ⅲ型变态反应，沉淀抗体是其特异性改变。第2个影响反应的因素是抗原的性质和来源，可能最主要的是尘埃微粒的大小，进入肺泡的最大的微粒为4～6μm，如多数是10μm以上的微粒，它们挂在上呼吸道，就没有足够的小微粒达到和损伤肺泡。第3个因素是暴露于有机物尘埃的情况，严重但间断暴露者与不太严重的长期暴露者的临床表现不同。一般认为是Ⅲ型变态反应(由于免疫复合物的沉着)，但肺活检未发现Ⅲ型变态反应的组织损害所特有的肺血管炎，因此，有人支持Ⅳ型变态反应(迟缓反应)观点，因为它的组织学损害在急性期是以肺泡壁为主的淋巴细胞浸润，继而是单核细胞浸润和散在的非干酪性巨细胞肉芽肿，后期是肺组织纤维化和机化的阻塞性细支气管炎，与Ⅳ型变态反应一致。但亦有报告指出Ⅱ型变态反应及非免疫学机制均参与此症的发病。本病多见于吸入抗原3～6h begin to appear symptoms.6～8h peaks24h around disappear, such as 'farmer's lung' caused by contact with moldy straw, 'pigeon breeder's lung' caused by allergy to animal protein in bird droppings, etc. Some reports indicate that there is a certain association between the histocompatibility antigen (HLA) system and allergic pneumonia. For example, 'pigeon breeder's lung' often occurs in white blood cells with HLA-A1.8indicates the existence of an immune response gene associated with the histocompatibility antigen system.

　　1Serum sickness:It refers to an immune complex disease that occurs concurrently with the injection of exercise immune serum, its main manifestations are rash, fever, joint pain, lymphadenopathy, etc.

　　2Vasculitis:It is the infiltration of inflammatory cells around the vascular wall and blood vessels, accompanied by vascular damage, including fibrin deposition, collagen fiber degeneration, and necrosis of endothelial and muscle cells, also known as angitis.

　　1Completely avoiding contact with pathogenic organic dust is the most fundamental preventive and treatment measure.

　　2Improve the production environment, pay attention to dust prevention, ventilation, and strictly follow the operational procedures, such as drying the hay and grain after harvesting before storing them in the barn.

　　3Keep the places where poultry are raised clean, and properly handle bird droppings.

　　4Keep the water in humidifiers and air conditioning systems clean to avoid contamination. Those working in environments polluted with organic dust should have regular medical surveillance.

　　5Those with obvious chronic respiratory diseases such as chronic asthmatic bronchitis, bronchial asthma, chronic obstructive pulmonary emphysema, and those with allergic constitution should not engage in close contact with organic dust jobs.

　　1Routine laboratory tests:Routine laboratory tests have little diagnostic significance, during acute attacks, peripheral blood pictures show increased white blood cells (15～25)×109/L, with increased neutrophils, but most without increased eosinophils.

　　2Immunological examination:Can be used for simple Ouchterlony biphasic gel diffusion technique detection, the serum contains specific precipitins IgG of allergens, which is helpful for diagnosis, but those who are exposed to allergens without symptoms in large quantities can also have precipitating antibodies against specific antigens, the gamma globulin can increase to20～30g/L, accompanied by IgG, IgM, and IgA levels elevated, IgE levels normal, serum complement normal, rheumatoid factor may be positive.

　　3Chest X-ray:The findings vary depending on the type of disease, with the acute type often showing diffuse small granulomatous infiltration of alveoli or interstitial pneumonia, as well as small nodular precipitates. In chronic cases, infiltration merges together, and X-ray changes are generally in3～6Months later, absorption, but severe cases can persist for a long time.

　　4Pulmonary function tests:Pulmonary function tests show restrictive ventilation impairment, dysfunction, including low vital capacity, reduced lung compliance, reduced diffusion capacity, no obvious airway obstruction and increased vascular resistance, local ventilation/perfusion ratio disorder, and decreased arterial oxygen saturation, which is more obvious during exercise.

　　Patients often have water, electrolyte, and acid-base imbalance in their bodies, so they should eat some foods rich in iron, such as animal livers and yolks; as well as foods high in copper, such as beef liver, sesame paste, pork, etc.; shrimp shells, dairy products, and other high-calcium foods can also be given:

　　1Eat less cold and cool fruits, as they can damage the Yang of the spleen and stomach, hinder the transportation and transformation function, and are not conducive to the recovery of the disease. Apples should be eaten in moderation and selected in the diet of pneumonia.

　　2Avoid spicy and greasy foods, as pneumonia is an acute febrile disease that consumes the body's vital energy, affects the function of the internal organs, and is prone to reduce digestive function.

　　1Avoid allergens, and at the same time, apply corticosteroid therapy (Prednisone30-60mg/d, medication1-2Weeks), which is the best way to terminate acute attacks. For cases with chronic fibrosis, the efficacy of corticosteroids is poor.

　　2In severe cases, adrenal cortical hormones can be given for treatment, but the specific dosage and treatment time have not yet been concluded. However, most scholars recommend taking prednisone (Prednisone) orally, starting with a daily dose of40～60mg2Weeks later, the dosage is gradually reduced, and the total course of treatment is4～6Months. Prednisone (Prednisone) can reduce the duration and mortality rate during the acute phase, but it cannot prevent the occurrence of chronic EAA. Small-dose hormone therapy can also be given to patients with chronic EAA, but the clinical effects vary greatly.