[Wheezing in infants and toddlers: new insights].

Wheezing in infants and toddlers is a common symptom, and these patients are difficult to approach--both diagnostically and therapeutically. Congenital conditions causing wheezing disorders should not be missed and--not all wheezy bronchitis is or will become asthma. Results from longitudinal studies indicate that the term "asthma" includes different phenotypes: so-called transient early wheezing, non atopic wheezing and atopic wheezing (asthma). Transient early wheezing is generally accepted to define recurrent wheezing in non-atopic babies or toddlers and tends to disappear by the age of 3. The primary risk factor is reduced pulmonary function since birth. The most common cause for non-atopic wheezing is viral infection, most frequently caused by respiratory syncytial virus. Infection with respiratory syncytial virus is a risk factor for ongoing wheeze during childhood but resolves in most children by the age of 13. Asthma can start at any age and is determined by a more chronic condition, provoked by a number of triggers in addition to viruses, frequently associated with a family history of atopy, early allergic sensitization and concomitant atopic dermatitis. Only asthma seems to be a progressive disease; and there is evidence from long-term studies that if anti-inflammatory interventions are started late, it might be too late to alter the natural course of the disease with its decline in pulmonary function. On the other hand, there is no evidence that small children with non-atopic wheezy bronchitis would benefit from long-term therapy with anti-inflammatory treatment; in this group a therapeutic trial with bronchodilators is sufficient. The diagnostic and therapeutic challenges of diagnosing asthma in this age group are considerable and require a comprehensive approach.