9p21 and the genetic revolution for coronary artery disease.

BACKGROUND It has long been recognized that 50% of the susceptibility for coronary artery disease (CAD) is due to predisposing genetic factors. Comprehensive prevention is likely to require knowledge of these genetic factors. CONTENT Using a genomewide association study (GWAS), the Ottawa Heart Genomic Study and the deCODE group simultaneously identified the first genetic risk variant, at chromosome 9p21. The 9p21 variant became the first risk factor to be identified since 1964. 9p21 occurs in 75% of the population except for African Americans and is associated with a 25% increased risk for CAD with 1 copy and a 50% increased risk with 2 copies. Perhaps the most remarkable finding is that 9p21 is independent of all known risk factors, indicating there are factors contributing to the pathogenesis of CAD that are yet unknown. 9p21 in individuals with premature CAD is associated with a 2-fold increase in risk, similar to that of smoking and cholesterol. Routine genetic testing will probably remain controversial until a specific treatment is developed. Over a period of 5 years, however, GWASs have identified 30 genetic variants for CAD risk, of which only 6 act through the known risk factors. SUMMARY The 9p21 variant has now been established as an independent risk factor for CAD and, along with the additional 29 risk genetic variants recently identified, is likely to provide the thrust for genetic testing and personalized medicine in the near future.