Scientists discover world's rarest blood group found only in 3 people
&imwidth=600&imheight=450&format=webp&quality=medium "Scientists discover world's rarest blood group found only in 3 people")
Blood spatter Photograph: (creative commons)
Scientists in Thailand have identified a rare B(A) hybrid blood type in just three people. Learn how blood types are determined and other rare blood groups like Rh-null, CRIB, and Gwada-negative.
Scientists in Thailand have uncovered more mysteries in the world of blood, beyond the commonly available blood groups, A, B, O, AB, with the Rh factor that determines positive and negative. They have found three individuals worldwide with hybrid B(A) blood type, one patient and two blood donors, after testing more than 544,000 blood samples. This is a genetic quirk found in approximately 0.00055 per cent of people.
How are blood types determined?
Blood types are identified by the antigens, or proteins/ sugars/lipids, which trigger an immune response when an alien object is found in the body. A-antigen has N-acetylgalactosamine as a dominant sugar, B-antigen is dominated by the sugar D-galactose, AB has both, O positive has rhesus or Rh, O negative has none of the above. For a successful blood transfusion, the Antigen of the donor have to match the Antigen of the receiver. This is why O-negative is a universal donor, as it lacks neither A nor B antigen, nor the Rh(D) antigen. All this information is encoded in the ABO gene of the ninth chromosome.
What is B(A) blood type?
The B(A) blood type is a genetic mutation of the ABO gene; the researchers found four variations of the ABO gene in these individuals. These variants modify the enzyme (glycosyltransferase) responsible for building antigen structures in red blood cells. So their red cells show a typical Type B profile but also express trace amounts of A-antigen. Meaning it is not fit for A/B/AB/O transfusion.
What are other rare blood types?
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O-ve blood group is found among only 7 per cent of the population in the world. While only 50 individuals have Rh-ve blood, completely devoid of Rh-antigen. In 2025, a 38-year-old woman in Kolar, Bengaluru, was found to have a blood group CRIB. In the same year, a European individual was discovered who had Gwada-negative blood, so unique that no compatible donor exists.
