SELECTED ARTICLES FROM THE RECENT LITERATURE 2004

12/14/04

Spectrum of severe wheezing in childhood

Summary
Background - Wheezing (Wh) is common in early childhood, sometimes severe. Both viral infections and allergies may play pathogenic roles in such childhood Wh but how much? And when?

Findings - The subject of severe Wh was recently reviewed in a recent editorial by Gern of the Univ. of Wisconsin in Madison . He commented specifically about a report by Hegmann et al in the same journal issue (J Allergy Clin Immunol 2004;114:239-47). Gern pointed out that viral infections caused most of the severe wheezing in infancy with allergies having little influence on this process. Respiratory syncytial virus (RSV) infections are particularly prone to cause severe wheezing in infants during cold weather months although more than one virus can be isolated from respiratory secretions in almost half of such cases.

Rhinovirus (Rh) infections are the main infections associated with infantile wheezing at other times of the year. It is not clear why some infants wheeze with Rh infections which are generally manifested as relatively mild URI. Some evidence suggests that certain factors characterize the infants with Rh-induced wheezing. There is an increased incidence of atopy (personal/family) particularly atopic dermatitis. In follow-up in later childhood there has been a 4 fold increased risk for asthma in those who had Rh-associated wheezing in infancy as compared to the asthma risk in children who had previously wheezed in infancy associated with other types of viral infections.

Viral infections are also important causes of wheezing in children at least 3 years old. However, these episodes occur mainly in the autumn with Rh as the major pathogen. Allergic sensitization and such viral infections are independent and synergistic factors for wheezing in this age group, including severe wheezing. Viral isolates were found in 50-70% of children and adolescents hospitalized because of severe wheezing. The nasal secretions may have been obtained too late for optimal viral isolation in some "virus negative" cases. Also, recently described viruses (e.g. metapneumovirus, certain corona viruses, additional Rh strains) may be not yet detected by current techniques.

In the "virus negative" severe wheezing episodes in older children, exposure to allergen in sensitive individuals may play roles. Exposures to dust mite and alternaria allergens seem particularly important in this regard. Air pollution (particularly tobacco smoke) is likely also a pathogenic factor.

Reference
J Allergy Clin Immunol 2004;114:236-8

Editor's Comments
These thoughtful comments help put the large amount of recent findings in this area into perspective. Viral infections appear to be the major factor in severe infantile wheezing, with this less of a sole factor as the child enters the second decade of life. At these later time points, combination of viral infection, allergen sensitization and possibly exposure to air pollution are the likely causal factors.

<-- BACK