What’s your blood type? For the vast majority of us, the answer is one of eight options: A positive, A negative, B positive, B negative, O positive, O negative, AB positive, or AB negative.
The ABO blood group system was the first to be identified, with those letters referring to the combination of A and/or B antigens on an individual’s red blood cells. This system determines which blood groups are compatible for transfusions, as certain combinations will result in the body attacking foreign blood cells. Additionally, some blood types have an antigen related to the Rhesus (Rh) factor protein, which determines whether the blood type is “positive” (the protein is present) or “negative” (the protein is absent).
Yet although these eight blood types are the most common, they are not the only blood groups. Some are exceedingly rare, and perhaps none is rarer than “Gwada negative,” a recently discovered blood type that has thus far been identified in only one individual.
In 2011, doctors in Paris noticed an unknown antibody in the blood of a 54-year-old woman from the French-controlled Caribbean island of Guadeloupe. The discovery happened during a routine blood draw before surgery. The case lay dormant until 2019, when researchers sequenced the woman’s entire genome and discovered a genetic mutation, inherited from both her parents. The mutation had resulted in an entirely unique blood type, which has been dubbed “Gwada negative,” a reference to the phonetic pronunciation of Guadeloupe. Researchers are now interested in determining whether any other individuals share this rare blood type.
Many other rare blood types have been previously identified outside of the ABO system, which is unsurprising considering that over 600 antigens can attach to red blood cells. This has resulted in dozens of rare blood group systems, defined as a blood type that occurs at a rate of 1 per 1,000 people or fewer, such as the Duffy blood group, Lutheran blood group, Kidd blood group, and K antigen group. The Rh-null group is exceptionally rare and is sometimes called “golden blood,” belonging to fewer than 50 individuals worldwide.
A mystery in the blood:
- Karl Landsteiner was awarded the 1930 Nobel Prize in Physiology or Medicine for his discovery of the A, B, and O human blood types. Landsteiner had solved a centuries-old mystery, explaining why previous transfusions had been so unsuccessful: when they occurred between patients with incompatible blood types, the red blood cells clumped together in a potentially deadly process called agglutination.
- People with O negative blood are known as universal donors, as their blood can be safely transfused to anyone with an A, B, O, or AB blood type. By contrast, people with AB positive blood can receive blood from any type (universal recipients).
- According to the CDC, over 14 million units of blood are transfused each year in the United States.
