Meet the Rarest Blood Type on Earth: Emm-Negative, or “Gwada Negative”
Move over, O-negative—there’s a new contender for the world’s rarest blood type, and it’s rewriting the rules of transfusion medicine. In June 2025, scientists officially recognized the Emm-negative blood type, also known as “Gwada negative,” as the 48th human blood group system. How rare is it? So far, only one living person on the planet is known to have it—and she’s the only one who can safely receive her own blood.
The Accidental Discovery That Changed Everything
The story unfolds like a medical mystery. Back in 2011, a 54-year-old woman in Paris was prepping for routine surgery. But when lab techs tried to match her blood, every test tube clotted in strange shades of mauve. None of the usual suspects—A, B, AB, O, or even the rarest Rh variants—were compatible. Stumped, the hospital called in specialists, but the case was shelved for years due to a lack of advanced genetic tools.
Fast-forward to 2019: high-throughput DNA sequencing revealed a mutation on the gene coding for the EMM antigen—a molecule found on virtually every human red blood cell. Missing this antigen meant her blood was unlike anything ever seen. After six more years of peer review, the International Society of Blood Transfusion unanimously voted to recognize Emm-negative as its own system, officially dubbed ISBT042.
Why Is Emm-Negative So Special?
The EMM antigen is what scientists call a “high-incidence” antigen—over 99.99% of people have it. Losing it is like removing the barcode from your groceries: suddenly, nothing scans right. For the Paris patient, this means her immune system treats all donor blood as a threat, potentially causing life-threatening reactions if she ever needs a transfusion.
Her only option? Autologous banking—stockpiling her own blood before any planned surgeries. As one French biologist put it, “She is the only person on the planet compatible with herself”.
How Does It Compare to Other Rare Types?
You might have heard of the “Bombay phenotype,” another ultra-rare blood group discovered in India in 1952. While Bombay patients face tough odds, they at least have a handful of matches worldwide. Emm-negative is even rarer—so far, no matches exist for the Paris patient, though similar cases have been reported in India and other parts of the world, bringing the global tally to just a handful of known cases.
The Challenge for Blood Banks
Ultra-rare blood types are a logistical nightmare for hospitals. A standard unit of red cells costs about $225 in the U.S., but rare types—especially those kept in deep-freeze—can cost ten times more. Emergency cross-border shipments add thousands more and precious hours in trauma cases.
To address this, French scientists are now screening blood samples from Caribbean communities, hoping to find more Emm-negative donors and build a frozen reserve. Meanwhile, researchers are racing to develop lab-grown red blood cells tailored to rare blood types—a solution that could be ready for clinical use within a decade.
What’s Next?
The discovery of Emm-negative blood is a testament to the power of modern genetics and the ever-expanding diversity of human biology. For now, the Paris woman at the center of this story leads an ordinary life, with an extraordinary asterisk on her medical chart: her blood is truly one of a kind.
As scientists continue their search for others like her, the story of Emm-negative reminds us just how much there is left to discover about what flows in our veins—and how a single patient can change the world of medicine forever.
