A genetic basis for heterogeneity of asthma syndrome in pediatric ages: adenosine deaminase phenotypes.

Wheezing in children is characterized by at least two major syndromes: "wheezing associated with respiratory infections" and "atopic asthma." The distinction between these two forms is not easy as similarities exist between them. The purpose of this study was to try to differentiate between them. We determined the phenotype of adenosine deaminase (ADA) in 291 children ages 1 mo to 15 yr who had been affected by attacks of wheezing recently requiring clinical attention. The results demonstrated that the frequency of 2-1 ADA phenotype was significantly reduced in wheezers compared to control subjects. Among wheezers, the 2-1 ADA phenotype was normally represented under 5 yr of age but was particularly rare among asthmatic children 5 to 15 yr old. Thus ADA phenotypes may represent a genetic basis for some of the heterogeneity of the asthma syndromes in children.