I was wondering what diseases/disorders and benefits only MAINLY occur in certain races. An example of this would be sickle cell anemia mostly occuring in black people.
I could spew a long tedious list, but I’ll simply point out that most diseases (except the very commonest) with a genetic component -not just ‘genetic diseases’ per se- tend to be found predominantly in one ethnic group or another. The reason is simple: same-ethnicity breeding has always been more common than cross-ethnicity breeding, so different ethnicities represent gene pools with relatively little spillover. This effect remains even in these “enlightened” times: a generation -or five- of ethnic moderate mixing isn’t enough to overcome centuries or millenia of fairly strong (if incomplete) genetic isolation
[re: “enlightened”: I don’t think there’s anything unenlightened about preferring partners who share ethnic, physical or socio-cultural values, or who might fit better into one’s community or extended family, but I personally find people who object to other people’s ethnic preferences “unenlightened”]
The exception would be diseases or disorders that are so common that we don’t say that we categorize them as “increased risk” rather than “predominantly in”. For example, there is a definite increased risk of hypertension among black Americans, which reflects itself in a constellation of increased incidences of otehr diseases, like renal failure. However, hypertension among white Americans is common enough to change the way we categorize the ethnic relation.
This can be a subtle point to some people, so let me clarify: hypertension and its related syndromes are present at sufficiently greater rates among black Americans that we would consider them ethnically linked, if they were not so common among whites as well (albeit often through somewhat different mechanisms). In reality, “hypertension” is a very broad term, and I’m inclined to take the view that “nothing Jack does changes what Jim does” – i.e. it’s not that there is no such thing as ethnically (genetically) linked hypertension among blacks, it’s more that there are different forms of hypertension that are predominantly found in blacks, whites, native Americans, etc.
However, I’m not sure that’s teh kind of answer you wanted, so I’ll offer a few ethnically linked disorders:
Northern European:
Cystic Fibrosis - 1 NE in 25 is a carrier (may be 1 in 25 caucasians in general)
Phenylketuria 1-2% of NE are carriers
Southern European:
A number of anemias and familial blood diseases
Ashkenazi (European) Jew
Type I Gaucher Disease - about 1 AJ in 19 is a carrier
Tay-Sachs (as noted above) - about 1 AJ in 25 is a carrier
Familial Dysautonomia - about 1 AJ in 35 is a carrier
Canavan disease - about 1 in 40 AJ is a carrier
Nieman Pick Disease - about 1 in 70 AJ is a carrier
Fanconi’s Anemia - about 1 in 90 AJ is a carrier
I don’t mean to suggest that Ashkenazi Jews have any greater susceptibility to genetic illness than Northern Europeans, it’s just that many of the “classic” conditions taught in med school happen to be AJ-linked, perhaps because of better family histories among immigrants or early availability of easy screening tests.
Sickle cell anemia, as noted, is mostly seen in those of African descent, but it is usually only a disease in people who inherit a sickle gene from both parents. In heterozygotes (with only one copy of the sickle gene) it may actually be beneficial for those who live in areas where malaria is endemic.
What is the source of your information, please?
Thanks.
Zoe, your question is a little undirected so I’m going to open my big mouth - any text on human genetics would cover the above. In many cases, if you Google on a particular disease you can find sites that list ethnicities at risk.
I think one reason so many disorders are named among Ashkenazi Jews is that, not only were they more inbred than the non-Jews they lived among (miscegenation laws prevented Jew/non-Jew marriage in many areas), but also that group has generated a fair number of doctors, who would of course be interested in diseases that affected their families.
And, on a final note - people seem fine with diseases/disorders affecting other groups, but not so much when it hits home. A WHO report a couple years back urged pre-natal testing and genetic counseling for all couples where one or both partners is at high risk for cystic fibrosis. The top of their list? all caucasians. It would have been amusing, if it weren’t so sad, to see medical “professionals” falling over each other protesting that you couldn’t call an entire race of people “high risk” - coincidentally, the protesters all seemed to be white. And they had never protested labeling all African-Americans as “high-risk” for sickle cell, or Ashkenazi’s as high risk for a half dozen disorders…
Just goes to show you scientists and doctors are flawed humans. Like the rest of us. 
On a related note, I just finsihed reading a book on genetic diversity in humans called Mutants: On Genetic Variety and the Human Body by Armand Marie Leroi which covers some fascinating territory in how the human form can go wrong. Some of the disorders are rare, some not, some ethnically linked, some not, some inherited, some not.
As noted earlier, the prevalence of diseases related to genetic conditions is generally a simple matter of intra-group marriage. People who marry people with similar conditions are more likely to produce children with similar conditions.
It should not be surprising that most of these conditions can be plotted geographically as easily as ethnically. In the case of the various conditions associated with the Ashkenazim, we find a pattern that is concentrated in Northeast Europe, with a further limitation to a specific highly endogamous group. The Ashkenazim have a wide dispersion of emigration, but it has occurred in only the last 125 years, so we can still see an apparent ethnic connection for any illnesses that have arisen among them. (Several of the “Ashkenazi” illnesses also occur among several other groups–in each case one in which there is a high rate of intramarriage. Tays-Sachs, I believe, has a high occurence among a specific group of French Canadians, for example.)
Similarly, while sickle cell anemia is often presented in the U.S. as a “black” disease, it is actually one of two genetic conditions that extends from Africa, through the Mediterranean region, across the Middle East, and into India. The variant that we generally associate with black people is most commonly seen in blacks in the U.S. because the majority of the blacks imported to the U.S. as slaves came from the high-malarial region of Africa in which it is endemic, while the number of white people who immigrated to the U.S. did not tend to come from the swampy regions of Italy, Greece, and Jordan where it is also endemic. (Had most U.S. slaves been imported from what is now South Africa rather than from what is now the African coast from Sierra Leone to Congo, we might not even consider sickle cell a “black” disease.)