Recently, I found out that two different people I know have thalassemia. I had never heard of this blood disorder before. Fortunately, they do not have significant symptoms and it is not contagious. Still, I wondered what it was and how come I’d never heard of it.
First, I was intrigued by the word. I recognized the “emia” having to do with blood and “thalasso” as having something to do with the sea, but this just confused me. American pediatricians Cooley and Lee first recognized in children of Greek and Italian immigrants in 1925 and the thalasso refers to the Mediterranean. The person I know with it of Italian descent had thought it was only people from the Mediterranean who have it. But it is actually more far-ranging than that.
Thalassemia is a group of inherited blood disorders, affecting the ability to produce hemoglobin. Hemoglobin is the iron-rich protein in red blood cells that carries oxygen and nutrients to your cells, as well as carbon dioxide from cells to be exhaled in the lungs. So, pretty important stuff.
Normal hemoglobin consists of four protein chains — two alpha globin and two beta globin, each connected to an iron-containing heme molecule. There are two genes code for the alpha chain and one for the beta. The different forms of thalassemia depend on whether the genes for the alpha or beta chain are affected and whether you have inherited the problem from one or both of your biological parents.
With one set of alpha genes from each parent, alpha thalassemia results from one to all four of the genes being deleted or damaged. This tends to affect those of southeast Asian, the Middle Eastern, and African descent. Those missing all four genes develop Hydrops Fetalis and usually do not survive. If fewer genes are affected, the result is often milder forms of anemia. Those missing one gene will be carriers, but usually live healthy lives. This is the case for the person I know of Chinese descent.
Beta thalassemia involves a total of two genes and most often affects people of Mediterranean descent, although some Chinese and other Asians, as well as those of African decent can also be affected. Thalassemia minor involves one gene. These people will be carriers, usually without symptoms, though minor anemia, can occur. This is presumably the case for the affected person I know, who is of Italian descent. Those missing both genes can have, either a milder form called thalassemia intermidea, or the more severe, thalassemia major, also known as Cooley’s Anemia (after the pediatrician). This results in various symptoms of poor health developing in the first year of life.
Thalassemia carriers might not notice any obvious physical symptoms so, if you are wondering, you could get tested. An examination of the blood could show that the red blood cells are smaller than normal (microcytosis). They may also have to specifically analyze the hemoglobin to be sure. Those with the beta trait will also have higher levels of hemoglobin A2 (another form of hemoglobin) and sometimes Hemoglobin F (the hemoglobin in fetuses), which use different globins other than beta. Those with alpha, have regular levels of hemoglobins A2 and F.
From an evolutionary standpoint, I wondered how this apparent genetic disadvantage could continue. It turns out that the smaller red blood cells of those with non-lethal forms of thalassemia can provide defense against malaria. I had heard about this in sickle cell anemia, which is related. But I wonder why I'd not heard of thalassemia. Maybe it's because blood conditions are not often part of normal conversations. Or maybe because it does not affect the populations that dominate the media I consume. Or maybe I had been told about it, but wasn't paying attention because I am squeamish around blood.
If you have insights about thalassemia, please share them below.