African American reduced susceptibility to arthritis?

A few years ago a brown friend of mine complained that there were all these diseases which non-white people were susceptible to at a higher rate (e.g., Type II Diabetes, hypertension, ateriosclerosis, etc.), perhaps the white race was really superior (or medical geneticists were entering into a conspiracy to prove that this was so). So with that, I point to a new PLoS Genetics paper, An African Ancestry-Specific Allele of CTLA4 Confers Protection against Rheumatoid Arthritis in African Americans:

Rheumatoid arthritis (RA) is a systemic autoimmune condition affecting the synovial membranes of diarthrodial joints. The etiology of RA is unclear but is thought to result from an environmental trigger in the context of genetic predisposition. We report that a single nucleotide polymorphism (SNP) (rs231778) in CTLA4, which encodes a negative regulator of T cell activation, is associated (p = 2.4Ã10â28) with protection from developing RA among African Americans. rs231778 is only polymorphic in populations of African ancestry. Protective alleles such as this one may contribute to the purported lower prevalence of RA in African Americans. Our finding appears to be independent from confounding by linkage with the HLA-DRB1 shared epitope or by genetic admixture. Furthermore, we did not replicate associations of CTLA4 SNPs with RA or other autoimmune diseases previously reported in Asians and Caucasians, such as rs3087243 (+60C/T) and rs231775 (+49A/G). The associations of different SNPs with RA susceptibility specific to different populations highlight the importance of CTLA4 in the pathogenesis of RA and demonstrate the ethnic-specific genetic background that contributes to its susceptibility.

1) "Genetic background" matters.

2) Don't stop at genetic background; the profiles of the population to which you belong are not necessarily your own profiles. Your genetic profile matters.