Introduction
Asthma is not strictly a disease in itself but a term used to describe a set of symptoms. Characterized by periodic attacks of wheezing breathlessness, it is caused by an obstruction of the airways which is variable in degree and largely reversible. This reversibility may be spontaneous or brought about by treatment.
The common factor in asthma is the abnormal hyperreactivity of the airways, which respond to a variety of chemical, physical and emotional stimuli. The production of mucus and the contraction of bronchial smooth muscles constrict the airways and prevent the normally passive process of expiration. The effort the patient must make to breathe out under these circumstances usually produces a wheeze, and possibly an irritating cough.
Asthma is conventionally divided into two types:
- Allergic asthma: Most often IgE-mediated in children, patients have IgE antibodies to one or several common allergens.
- Non-allergic asthma: Patients do not demonstrate allergen-specific IgE antibodies, but show a non-specific bronchial hyperreactivity.
The vast majority of children with asthma have allergic asthma, although very young children often exhibit bronchial hyperreactivity in response to respiratory infection (viral induced wheeze).
Prevalence
Asthma is the most common chronic disease in children. It occurs twice as often in boys as in girls, but this difference disappears towards adolescence. As many as 21-34% of children suffer from recurrent wheezing in early childhood and 30-60% of them seem to be sensitized and have allergen-specific IgE to one or more allergens. 7-10% of school age children will experience asthma attacks and most of them will have allergen-specific IgE antibodies. The majority of asthmatic children develop symptoms before the age of 5.