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Bronchial asthma

Synonym: Asthma

German: Asthma bronchiale

1 Definition

Bronchial asthma is a chronic, inflammatory disease of the respiratory tract, which is characterized by bronchial hyperreactivity and respiratory obstruction.

2 Etiology

The development of bronchial asthma is a multicausal process, which is caused by exogenic factors (environmental factors), and also by genetic dispositions. In addition, the course of the disease can be influenced by climatic changes and mental factors. Important exogenic activators are: · Allergens o Environmental allergens (house dust mites, pollen) o Allergenic work substances (flour) o Food allergens · Toxins or chemical irritants · Respiratory diseases · Pseudoallergic reactions (PAR) to analgesics (analgesic-induced asthma) · Physical exertion (mainly in children) Patients with allergic asthma or other atopical diseases show a polygenic inherited trait for an overshooting immune response of IgE. If both parents suffer from atopy, the children have an atopical disease as well in 40-50% of the cases.

3 Epidemiology

As a rule, bronchial asthma already occurs in infancy and is the most common chronic disease of this stage of life. There exist differing statements on the prevalence of bronchial asthma in Germany. Some authors mention 2-4%; other sources even 6-10%. The number of deaths caused by asthma in Germany is approx. 5000/year.

4 Classification

4.1 ...According to etiology

  • Allergic or extrinsic asthma
  • Non-allergic or intrinsic asthma
  • Mixed forms

4.2 ...According to degree of severity

  • Grade 1: Intermittent
  • Grade 2: Persistent, mild
  • Grade 3: Persistent, moderate
  • Grade 4: Persistent, severe

5 Pathophysiology

Genetic disposition and exogenous noxa trigger three pathophysiological processes which characterize bronchial asthma:

5.1 Inflammation of the bronchi

Allergens or infections elicit an infectious reaction of the bronchial mucous membrane. In allergic asthma, an IgE-induced reaction of the immediate type (Type 1 reaction) occurs immediately after inhalation of the allergen. The mast cells in the mucous membrane degranulate and thereby release inflammation mediators like histamine, ECF-A, bradykinin and leukotrienes ("immediate reaction"). Apart from this immediate reaction, there also exists an IgG-induced late reaction after 6-12 hours or a combination of both reaction types ("dual reaction"). As a rule, the triggering allergen can only be identified at the early stage of the disease. In the course of years, the range of allergens often becomes wider, thereby making it more difficult or even impossible for the patient to avoid allergens.

5.2 Bronchial hyperreactivity

An unspecific bronchial hyperreactivity can be detected in almost all asthmatics. In case of the inhalation of irritants, the hyperreactivity manifests as a very strong constriction of the bronchial tubes, and can be objectified by the methacholine test.

5.3 Endobronchial obstruction

The endobronchial obstruction is quasi the first clinically discernible "end product" of the pathophysiological processes of bronchial asthma. It develops through the shift of the bronchial lumen as a consequence of mucosal edema, increased mucus secretion (dyscrinism) and bronchospasms.

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