Asthma is a disorder of the bronchial tree, characterized by: a) airway hyperresponsiveness to many physical changes and to chemical and pharmacologic agents, b) inflammatory changes of the bronchial mucosa and c) mild to severe obstruction of airflow. Although asthma frequently begins in childhood, estimates of its incidence in the various age groups vary widely: most children develop asthma before age 8, and almost 50% before age 3. However, its real incidence before age 5 is difficult to assess because of: a) problems in obtaining clinical or epidemiological information and b) the variety of factors (recurrent viral infections, gastroesophageal reflux, etc) able to induce inflammation and hyperresponsiveness of the airways which can easily be misinterpreted as asthma. Atopy, the state of allergic responsiveness to common inhaled antigens, plays a key pathogenetic role in most cases of childhood asthma and the familial association between this disorder, and other allergic disorders such as atopic rhinitis and dermatitis has suggested a common genetic basis. More recently, it has been demonstrated that atopic IgE responsiveness segregates as an autosomal dominant character and is significantly cotransmitted with a variable genetic marker on the long arm of chromosome 11. However, since only a proportion of atopic subjects actually has asthma, other factors must interfere with the dominant inherited IgE responsiveness to produce clinical significant disease. Sex hormones are probably involved since, before puberty, asthma occurs 1-3 times more frequently in boys than in girls, while in adolescence this difference between sexes tends to disappear. In addition to atopy, a number of factors may initiate airway responsiveness or precipitate asthma. They include: a) bronchiolitis in infancy, b) viral infections, c) exposure to allergic factors, d) exposure to passive cigarette smoking, e) exposure to chemical irritants. These same and other factors, once asthma develops, may precipitate or aggravate symptoms. Problems incompletely solved are the natural history of the disease, i.e. how many children 'outgrow' their asthma, and how to identify this subgroup. Finally it is not clear whether intensive therapy, early in the course of asthma, or persistent therapy can prevent the disease becoming chronic.
|Number of pages||4|
|Journal||European Respiratory Review|
|Publication status||Published - 1993|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine