Race in biomedicine: Encyclopedia II - Race in biomedicine - Disease association studies

Race in biomedicine - Disease association studies

Race is associated with differential disease susceptibility and environmental responses. Many highly penetrant Mendelian diseases that are caused by mutations in a single gene are known to be found at higher frequencies in certain races. The HbS allele that causes haemochromatosis is found at higher frequencies in sub-Saharan Africans and Southern Europeans. Similarly, the ΔF508 allele of CFTR that causes cystic fibrosis is found in higher frequencies in Northern Europeans. It is believed that many of these mutations first occurred in the population that is most affected.

Race has also been found to be associated with susceptibility to complex, multifactorial and multigenic diseases. The incidence and death rate of prostate and breast cancers are significantly higher in African-Americans than European-Americans. Higher proportions of individual African ancestry is associated with increased susceptibility to both obesity and abnormal levels of insulin secretion. Likewise, Hispanic, American Indian, African American, Pacific Island, and South Asian ancestry is considered a risk factor for diabetes. Also, the incidence of heart disease and high blood pressure is higher in African-Americans than European-Americans.

The common disease-common variant (often abbreviated CD-CV) hypothesis predicts common disease causing alleles will be found in all populations. An often cited example is an allele of apolipoprotein E, APOE ε4, which is associated in a dose-dependent manner with susceptibility to Alzheimer's disease. This allele is found in Africans, Asians and Europeans. However, many disease causing alleles are found to have different (technically called epistatic) effects in different populations. For example, the increased risk of Alzheimer's disease that is associated with the APOE ε4 allele is 5-fold higher in individuals with Asian rather than African ancestry.

Polymorphisms in the regulatory region of the CCR5 gene affect the rate of progression to AIDS and death in HIV infected patients. While some CCR5 haplotypes are beneficial in multiple populations, other haplotypes have population-specific effects. For example, the HHE haplotype of CCR5 is associated with delayed disease progression in European-Americans, but accelerated disease progression in African-Americans. Similarly, alleles of the CARD15 (also called NOD2) gene are associated with Crohn's disease, an inflammatory bowel disorder, in European-Americans. However, none of these or any other alleles of CARD15 have been associated with Crohn's disease in African-Americans or Asians.

Adapted from the Wikipedia article "Disease association studies", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki