Present and future treatment of asthma in infants and young children.

Asthma is a chronic inflammatory disease of the airways characterized by the local production of inflammatory mediators and an increase in recruitment of inflammatory cells (predominantly eosinophils and mast cells). It has been proposed that the chronic nature of this inflammatory response may be responsible for long-term pulmonary changes including bronchial hyperresponsiveness, airway remodeling, and irreversible airflow obstruction. Much of the information available on the pathogenesis of asthma is based on studies performed in young adults. Because of numerous complications, studies in infants and young children are often difficult to conduct; therefore information on this age group is lacking. Although studies are limited, data suggest that an asthma-like inflammation is present at a very early age, with increases in inflammatory cells and thickening of the lung basement membrane detected in infants and young children. In addition, lung function of children with persistent wheezing was significantly lower by 6 years of age compared with children who had no wheezing episodes during the same period; differences between groups were not apparent at 6 months of age. These data suggest that airway inflammation in young children with asthma is associated with nonreversible impairment of lung function. Recent National Asthma Education and Prevention Guidelines stress the importance of anti-inflammatory agents, particularly inhaled corticosteroids, in the treatment of young children with persistent asthma. Given data supporting the presence of an inflammatory response early in the disease course, early intervention with anti-inflammatory agents may be indicated at the onset of symptoms to prevent long-term, irreversible, impairment of lung function. Although several studies have shown that inhaled corticosteroids may be effective in the treatment of recurrent wheezing in infancy, tools need to be developed to distinguish infants with early-onset asthma from those with transient wheezing.