Jul 08, 2009
The causes of asthma are largely unknown. Asthma is most likely a multifactorial condition, which means it involves a combination of genetic, lifestyle and environmental factors.
Some non-genetic factors that have been proposed to increase susceptibility to asthma include having recurrent childhood respiratory infections, secondhand smoke exposure, low birth weight, being overweight, living in an urban area, and exposure to certain chemicals (such as chemicals used in farming, manufacturing, and hairdressing).
It is currently well established that asthma also runs in some families. Researchers believe that there are probably a number of genes that affect the development and symptoms of asthma as well as affect a person's response to certain asthma medications.
Variations in many genes have been identified in some families, but no one gene has been strongly associated with asthma.
Variations in the ADRB2 gene have been associated with asthma susceptibility. In addition, a particular variation (arg16) in the ADRB2 gene has been shown in several studies to alter the body's response to beta-agonists, a type of medication used to treat asthma. Beta-agonists include albuterol, salbutamol, and salmeterol. We all have two copies of the ADRB2 gene. A little less than 20% of the U.S. general population has two copies of this variation, one in each gene. The effectiveness of albuterol as a rescue therapy may be reduced in these individuals when beta-agonists are used as a routine treatment for asthma.
Single nucleotide polymorphisms (SNPs) are small variations in a single "letter" of DNA that can be found throughout our entire genetic make-up. Some researchers have proposed that specific SNPs may influence the risk to develop asthma in some people. How (or whether) many of these SNPs contribute to asthma is still unclear. Research is currently often limited to specific ethnic groups. Further research is needed to replicate study findings across different ethnic groups and clearly establish associations.
Other yet to be identified or adequately classified genes may also contribute to asthma.
For more information on the genetics and inheritance of asthma, visit: http://AccessDNA.com/condition/Asthma/409