It turns out that sickle-cell anaemia is not the only drawback to hereditary malaria-immunity.
A U.S. Government website says this: “African American women are three times as likely as white women to get lupus. African American women tend to develop lupus at a younger age and have more severe symptoms than white women.” The disease affects mainly females. ) I am wondering if an analysis of the sample identified as “white women” would further define the populations that have this order and those that do not. It seems entirely likely, given that some of the populations customarily called white, like Jews, have significant Negro admixture.
If there are any people of strictly European ancestry that have this mutation, they would most likely be descended from coastal or other lowland populations, since malaria does not occur except where there is a habitat for mosquitoes.
For some reason, it is difficult to find representations of the disease online that feature Asians or Negroes, even though they are the ones above all that suffer from it. In this illustration published by Aurora Health Care, they make the disease-sufferer White and male, which is the least likely demographic to suffer this hideous affliction! (I wonder if they also present an image of a worried man with their breast-cancer literature.) I will spare you the sight of a skin-diseased Negress, although I did find a couple of such images.
From the Los Angeles Times:
A group of scientists think they’ve figured out why the autoimmune disease lupus afflicts people of Asian and African descent at higher rates than Caucasians.
Their theory: A form of a gene that raises risk of lupus has a plus side — rendering the carrier more resistant to malaria.
That means the gene would be useful, and selected for, in areas of the world where malaria is rife. In those places, the downside of increased lupus risk would be far outweighed by the added protection against malaria.
And — like a fossil — the gene variant would persist in the DNA of people whose ancestors came from malaria regions, even when those people don’t live with the threat of malaria.
The study, conducted by a team of British researchers, was published in the journal Proceedings of the National Academy of Sciences. It found higher rates of the gene variant in Hong Kong patients with lupus compared with matched controls — and it found lower rates of the gene variant in children in Kenya who had gotten malaria compared with the general population there.
The gene in this case (known as Fc gamma RIIB) is a receptor involved in the immune response, and so the finding makes sense — a ramped up immune system would help fight infection but could also raise the risk for autoimmune conditions.
It’s a similar story to that seen with the gene for sickle cell disease. This gene protects against malaria, but when a person has two copies of it, it causes the sickle-cell blood disease. Rates of the mutations causing sickle cell disease remain higher in African Americans today.