Exercise-induced bronchoconstriction : clinical studies in childhood asthma

At present, astluna is regarded as a chronic inflammatory disorder of the airways, In susceptible individuals, asthma causes symptoms, that are usually associated with variable, but often reversible airflow obstmction. Astlulla is the most conunon lung disease in childhood, with a symptom-based asthma prevalence of approximately 11% in The Netherlands. Vorldwide, asthma prevalence appears to be on the increase. Although mortality rates are low, asthma causes significant morbidity and school absenteism in children. The clinical expression of asthma varies from patient to patient and from time to time within each patient. Anamnestic features suggestive of a diagnosis of asthma are intermittent episodes of wheezing, chest tightness and shortness of breath, as well as recurrent or persistent cough. Symptoms may worsen at night or in the early morning, and are precipitated by viral infections, allergen exposure, exercise, chemical irritants, tobacco smoke and strong emotional expressions. Diagnosis may be especially difficult in infancy. Wheezing in infancy as a reflection of early-onset asthma appears to be associated with increased sensitization to allergens and a deterioration of lung function in the first 6 years of lifes. Risk factors for development of asthma in older children and adolescents also include atopic sensitization as well as the occurence of bronchial hyperresponsiveness (BHR). The BHR in children decreases with age, but the tendency to retain BHR is closely related to markers of atopy, such as serum IgE levels and positive skin prick tests II. These epidemiological data underline the close association between atopy, BHR and asthma. Supportive evidence for a genetic basis of this association has now been provided by the identification of a gene cluster on chromosome 5, linked to both elevated IgE levels and BHR".