Humans have 44 blood group systems, and the list is essentially settled
The core idea stands, but key numbers or details have changed.
TaughtBeyond ABO and Rh, blood typing is a mostly closed book. The International Society of Blood Transfusion recognises a fixed roster of blood group systems, 44 of them, and the mysteries were solved long ago.
NowIn 2024, researchers at NHS Blood and Transplant and the University of Bristol described the MAL blood group system, the 47th recognised system, finally explaining the AnWj antigen, whose genetic basis had been a mystery since 1972.
What actually happened
The roster is not closed and never quite was; it grows as the biology gets pinned down. AnWj was discovered in 1972, but nobody knew which gene carried it. The team showed the antigen sits on the Mal protein, and that rare people who lack it have deletions in the MAL gene, turning a 50-year puzzle into a defined, testable blood group.
This is 'updated,' not a revolution: ABO and Rh still matter most, and MAL-negative blood is vanishingly rare. But it is quietly important. Identifying these patients lets hospitals genotype and match blood for the handful of people worldwide each year who would otherwise face dangerous transfusion reactions, and it nudges the textbook count upward again.
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Who was taught this
Still standard through 2024, so anyone who finished school between 1950 and 2024 learned the earlier version.