Phenotypic Expressions of Asthma

Asthma has frequently been referred to as a syndrome, rather than a single disease. There are a number of clinical presentations to support this philosophy. Infants and young children often have wheezing problems. Since a variety of clinical conditions can present with wheezing, this age group is not routinely studied in genetic evaluations.

Children over six years of age with asthma are routinely included in genetic studies of asthma. Atopy (a probably inherited allergy) is an important contributing factor to asthma in the pediatric age group, and most genetic studies have used this associated feature in their definition of an individual with asthma. The issue is whether it is the asthma condition or the atopic status that is identified by the analysis.

Another clinical presentation of asthma is usually seen in adults, in whom a readily identifiable allergic trigger is often absent. To date, the so-called intrinsic asthmatic has not been separately studied using genetic approaches.

Asthma clearly has different clinical expressions. This requires the researchers involved in genetic studies of asthma to select an asthma type that is consistent for each person enrolled in a genetic study. A particular study must also use population, racial, and, possibly, environmental factors.

Source:Bruce Ryhal, M.D., Allergies and Asthma in Sports