Who doesn’t love learning about a fun genetic disease? And what is more fun than a disease that can turn you blue?!Hemoglobin is a protein found inside your red blood cells that allows your cells to bind and carry oxygen. Kind of a super important protein. In mammals, 97% of a red blood cell is hemoglobin. A hemoglobin molecule is made up for 8 subunits: 4 protein subunits and 4 iron containing subunits (hemes). The heme groups are what bind, carry and release oxygen molecules. Of the 4 protein subunits, there are 2 types: alpha-globin and beta-globin. A gene called “hemoglobin, beta” (HBB) is what tells the body how to make the beta-globin subunit.
Methemoglobinemia (beta-globin type) is a rare genetic disorder of the blood. Individuals with methemoglobinemia have a few mutations in certain parts of the HBB gene. These mutations cause the body to produce an atypical version of the beta-globin subunit. When this odd version joins the other subunits to form a hemoglobin molecule, it doesn’t join together properly and ends up forming a slightly different protein, hemoglobin-M.
Hemoglobin-M does not interact with the heme groups properly and ends up inhibiting their ability to bind oxygen as well as normal. Poor binding means less oxygen being delivered throughout the body.
We all know that oxygenated blood is red (visualize your arteries, blood dripping from a cut, etc.) and deoxygenated blood is bluish in color (think of your veins). Less oxygen in the bloodstream will make the blood blue as it moves through the body, causing the skin and other membranes of a person with methemoglobinemia to look blue.
A person inherits methemoglobinemia from their parents. It is an autosomal dominant trait. Autosomal means it is not sex-linked (not on an X or Y chromosome); the mutation can come from the mom or dad and will affect both sons and daughters. Dominant means that it only takes one copy of the mutated gene to have the condition. If both parents are blue, there is a very slim chance any children will be normal colored (the best being a ¼ chance if the parents are both heterozygous carriers).
There is not really a treatment to fix this condition, but as long as the person doesn’t mind being blue they will be fine. Most people with methemoglobinemia live very normal lives. The most famous case of methemoglobinemia was the Blue Fugates of Kentucky. After emigrating from France in 1820, Martin Fugate married Elizabeth Smith of Kentucky. They had 7 children and 4 of them popped out blue. Being in the backwoods of Kentucky, the kids obviously married other locals and eventually started inbreeding. The whole area started turning blue. Three blue Fugates were still alive in the 1980s.
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