A new study reveals an especially rare blood type that was not known until today – and only three people in the world have it. The discovery, which was made almost by accident, took place as part of a large study in Thailand that examined more than 550,000 blood samples from donors and patients.
The researchers, who conducted a retrospective review of 285,450 blood donors and 258,780 patients, sought to identify irregularities in the ABO blood type system. In practice, fewer than 400 mismatches were found – but three of them turned out to be a phenomenon never seen before: A new blood type called B(A).
What does this even mean?
The ABO blood type system, discovered at the beginning of the 20th century, determines our blood type according to sugars and proteins found on the surface of red blood cells.
• A sugar called N-acetylgalactosamine defines blood type A.
• A sugar called D-galactose defines blood type B.
• The presence of both creates type AB.
• The absence of both – type O.
All this is determined by the ABO gene, located on chromosome 9.
But occasionally, irregularities called “ABO mismatches” are discovered – situations where forward blood typing (testing blood cells) and reverse typing (testing antibodies) do not agree with each other. Although they are very rare, they can be critical in the case of a blood transfusion.
Three exceptional cases
Among the hundreds of thousands of samples, only three people presented a pattern that had not been observed before: They were classified as type B, but tests found partial activity of antigen A, something that should not appear at all in regular type B blood.
Genetic tests revealed that the three individuals carry four unique mutations in the ABO gene – different from any other blood type ever documented, including similar rare cases in other Asian populations.
For the three individuals themselves, the discovery is not expected to affect daily life. It may complicate a future blood transfusion, but in cases of need, type O-negative blood units can be used, which are considered “universal donors.”
For the scientists, whose study was published in the journal Transfusion and Apheresis Science, this is a sign that the blood type classification system is still far from being fully understood. Alongside other rare blood types – such as “golden blood” (Rh-null), found in fewer than 50 people worldwide, or “Gwada-negative,” identified in a single person – the new discovery suggests that more blood types likely exist that have yet to be found.