OVERVIEW
Dust mite allergic asthma, a form of allergic asthma. Dust mites are important allergens that induce bronchial asthma. In recent years, a large number of studies have confirmed the close relationship between dust mites and bronchial asthma, and that they are important triggering factors for bronchial asthma.
Etiology
Dust mite-induced airway inflammation is the main cause of dust mite allergic asthma. Pyroglyphid mites predominate in house dust mites, accounting for more than 90% of the cases. House dust mites use human or animal shed dander as their main food source. The temperature, humidity, and food source on the bed are suitable for the growth and reproduction of house dust mites. A person can produce about 0.7g of dander per day, which gives the dust mites on beds a sufficient food source. Therefore, the high content of dust mites in bedding may be an important cause of bronchial asthma attacks caused by dust mite allergy.
Symptoms
The onset of asthma in infants and young children is often preceded by 1 to 2 days of upper respiratory allergy symptoms, including itchy nose, sneezing, runny nose, rubbing the eyes, rubbing the nose and other manifestations, and gradually coughing and wheezing. Elderly children tend to have a more sudden onset, often starting with a coughing bout, followed by wheezing and dyspnea.
Examination
1. Measurement of specific IgE in the serum
IgE >40U/ml (or >4ng/ml) can be recognized as a positive reaction. When >200U/ml (or >20ng/ml), it can be judged as strong positive reaction.
2.Determination of serum dust mite specific IgG, IgA
Measurement of dust mite-specific IgG is also important for the diagnosis of dust mite allergic asthma.
3. Skin prick test
It is more commonly used, and it is generally believed that if the dust mite infiltration preparation containing dust mites for 20-70 days is used for the test, and the diameter of the air mass is more than 5mm, it can be judged as positive reaction.
4. Bronchial excitation test
Inhalation of dust mite allergens can simulate the induction of dust mite allergic asthma attacks, is a more reliable means of detection to diagnose this disease.
Diagnosis
Specific immunodiagnostic test not only has important reference value for the diagnosis of dust mite allergic asthma, but also can guide the prevention of dust mite allergic asthma, immunotherapy and efficacy evaluation, the main test methods are as follows.
1. Skin test
Through the skin prick test or intradermal injection test injected dust mite allergenic dip preparation to assist the diagnosis of dust mite allergic asthma and epidemiological investigation, the method is simple, inexpensive, safe, but the positive standard has not yet been fully unified, the skin prick test is more commonly used, it is generally believed that the use of the dust mite containing 20-70 days of the dip preparation for the test, the diameter of the dust mite in more than 5mm can be judged as a positive reaction, and then from the subject’s blood serum, the test can be carried out. At this time, dust mite-specific IgE antibodies can often be detected in the serum of the examinee, and the reproducibility is high. At present, the commonly used dust mite allergens by w/v method, total nitrogen assay and protein nitrogen unit assay are often not accurate enough for skin test or other specific tests due to poor accuracy and lack of standardization.
2. Dust mite inhalation bronchial provocation test
Inhalation of dust mite allergens can simulate the triggering of an attack of dust mite allergic asthma and is a more reliable test for the diagnosis of the disease. In addition to the bronchial excitation test, the environmental excitation test is also commonly used. Environmental excitation test is a more reliable method of excitation through natural contact with dust mites. Compared with the test method of using dust mite allergen immersion preparation, the environmental excitation test is more in line with the natural state no matter in the way of contacting allergens, the quantity, or in the morphology of antigens, which greatly improves the credibility of the test, but the environmental excitation test is difficult to be standardized, coupled with the requirements for the specificity of the environment and other more stringent, it is difficult to be used in routine diagnosis and epidemiological testing. However, it is difficult to standardize the environmental stimulation test, and the requirements for environmental specificity are more strict, so it is difficult to be used in routine diagnosis and epidemiological investigation.
3. Serologic examination
(1) Determination of serum dust mite-specific IgE Currently, radioimmunosorbent assay (RAST) and enzyme-linked immunosorbent assay (ELISA) are mostly used for detection. With the advantages of high sensitivity, repeatability, automatic operation, etc., it is a common method to diagnose dust mite allergic asthma, and the dust mite antigen used in the determination should be the international standardized dust mite allergen dip preparation. Positive reaction can be judged when specific IgE in serum is >40U/ml (or >4ng/ml). When >200U/ml (or >20ng/ml) can be judged as a strong positive reaction.
(2) Determination of serum dust mite-specific IgG and IgA The determination of dust mite-specific IgG and IgA has important reference value for the diagnosis of dust mite allergic asthma, but the positive rate is usually lower than that of dust mite-specific IgE, so most authors believe that it is not appropriate to use it as a routine diagnostic index, and it is currently mostly used in clinical research.
(3) Dust mite-specific T-lymphocyte assay In the Second International Collaborative Conference on Dust Mite Allergy and Asthma, five authors reported that dust mite-specific T-lymphocytes were similar to murine “Th2” cells, while T-lymphocytes from non-allergic patients were similar to “Th1” cells. T lymphocytes from non-allergic patients were similar to “Th1” cells. These data provide the best evidence for the existence of “Th1” and “Th2” cells in humans. The detection of dust mite-specific T-lymphocytes is still at the basic research stage.
Treatment
Although prevention of dust mite asthma is important, it is not a substitute for treatment. Treatment should be based on or in conjunction with preventive measures, and the main treatment methods include specific treatment and non-specific treatment.
1. Specific treatment
It mainly refers to the desensitization treatment by using dust mite allergen dip, also called dust mite allergen immunotherapy. This kind of therapy is the most widely used treatment method in allergic reaction clinic, which has the significance of etiological treatment and also has the nature of prevention. Dust mite allergen immunotherapy can effectively improve the symptoms and lung function of patients with dust mite allergic asthma, and after long-term treatment can also reduce airway hyperresponsiveness, inhibit delayed-phase asthma response, and is important in improving the patient’s tolerance to dust mites. Pre-seasonal immunotherapy can be used for patients with seasonal episodes of dust mite-allergic asthma, while for patients with perennial episodes, year-round conventional immunotherapy is required. There are dozens of allergenic dip preparations available for treatment, several of which have been approved by WHO or FDA.
2. Non-specific treatment
(1) Antihistamine therapy Many antihistamines have good clinical efficacy in dust mite allergic asthma, especially the second generation antihistamines such as azelastine, cetirizine, terfenadine (terfenadine), loratadine and so on discovered in recent years, which can effectively improve the symptoms, and they are the main medicines for the treatment of mild dust mite allergic asthma at present, among which some medicines, such as azelastine, not only antagonize histamine, but also can Some of these drugs, such as azelastine, can not only antagonize histamine, but also antagonize inflammatory mediators such as leukotrienes, platelet-activating factor, and thromboxane A2.
(2) Glucocorticoid inhalation therapy For patients with moderate or severe dust mite allergic asthma, glucocorticoid inhalation therapy can achieve good therapeutic effect, and the types of inhaled drugs include beclomethasone (beclomethasone dipropionate), budesonide (butyldelethasone), fluticasone propionate, acetone acetylide dexinflammation, betamethasone valerate and so on, and glucocorticoid inhalation therapy is the most important measure in the treatment of moderate or severe dust mite allergic asthma. Glucocorticoid inhalation therapy is currently the most important measure for the treatment of moderate and severe dust mite allergic asthma, and is recommended as the drug of choice by many authors.
(3) Symptomatic treatment can be inhaled or oral bronchial antispasmodic during acute asthma attacks, and systemic glucocorticoid therapy can be considered when the condition is severe.