The Effect of Adrenergic β2 Receptor Thr164Ile Gene Polymorphism on Asthma Risk, Severity and Response to Β2 Agonists in Egyptian Children Background: Asthma is a global health problem affecting millions of adults and children. Pathogenesis of asthma is multifactorial and the genetic component is of particular importance. Objectives: To assess the role of ADRB2 Thr164Ile gene polymorphism in asthma risk, severity and response to β2 agonist therapy in Egyptian children. Methodology: The study enrolled 50 asthmatic and 50 control children. Pulmonary function tests and serum levels of IgE of asthmatic children were measured. The Thr164Ile genotypes were detected for all study subjects by Amplification Refractory Mutation System- Polymerase Chain Reaction (ARMS-PCR). Results: Serum IgE levels were significantly higher on comparing mild to moderate and severe cases (P=0.002& 0.02, respectively). The Ile/Ile genotype of Thr164Ile SNP was significantly present in asthmatic subjects (P=0.039). The Thr164Ile SNP was associated with lowered response to β2 agonist inhalation.