rs2240017

This SNP encodes a variation in the 33rd amino acid of the protein encoded by the TBX21 gene. Although 95% or so of all Caucasians carry two copies of the rs2240017(G) allele, as oriented in dbSNP orientation, and are thus rs2240017(G;G) homozygotes, a few individuals are rs2240017(C;G) heterozygotes. These heterozgotes are reported to improve better over time in response to corticosteroid treatment for asthma than the rs2240017(G;G) homozygotes. So far, studies have not linked, however, this SNP to any change in the overall risk of asthma itself. Although the effect observed was strong, in that treating rs2240017(C;G) heterozygotes ultimately (over 4 years) yields average airway responsiveness in the normal range (i.e. in the same range as for nonasthmatics), the authors point out that the relatively small number of heterozygous children studied indicates that a larger study is warranted to ensure reproducibility. It is also unknown whether the effect is limited to the particular corticosteroid used (budesonide, aka Rhinocort) in this study. This is thought to be unlikely, though, given the general nature of the drug.