Scientists Discover Rare New Blood Type Found in Only One Woman

A newly discovered blood type has scientists intrigued — because it’s been found in just one person in the entire world.

Researchers have identified a previously unknown blood group in a 68-year-old woman from Guadeloupe, a French overseas territory. The rare blood type, now named “Gwada negative”, after a local nickname for Guadeloupe, was introduced during the International Society of Blood Transfusion’s Congress in Milan, which concluded on June 4.

The Case That Stumped Scientists for Years

The discovery stems from a case that began more than a decade ago. In 2011, the woman, then living in Paris, underwent standard blood tests ahead of surgery. But the results didn’t match any known blood types. At the time, lab techniques weren’t advanced enough to explain the anomaly, and the case was set aside.

In 2019, researchers reopened the file using high-throughput gene sequencing, a modern DNA analysis tool that allows for faster and deeper genetic insights. What followed were two years of research, during which the woman’s entire genome was sequenced.

Understanding Blood Types: More Complex Than You Think

Most people are familiar with the ABO and Rh (Rhesus) blood group systems. These systems are based on the presence or absence of certain antigens — proteins or sugars — on red blood cells. Discovered in 1901 by Austrian-American scientist Dr. Karl Landsteiner, the ABO system earned him the Nobel Prize in 1930.

The ABO and Rh systems create the eight main blood types: A+, A−, B+, B−, AB+, AB−, O+, and O−. However, there are many other blood group systems beyond these, which can also impact compatibility for transfusions. As of 2024, the International Society of Blood Transfusion (ISBT) had recognized 45 such systems. The recent addition of Gwada negative makes it number 48.

What Makes “Gwada Negative” Unique

Scientists found that the woman’s unique blood type is the result of a mutation in the PIGZ gene, which affects how proteins attach to the surface of blood cells. This mutation causes her cells to carry unique antigens not found in any other known blood types.

“She is the only person in the world compatible with herself,” said Thierry Peyrard, a biologist at Établissement français du sang (EFS), France’s national blood service.

This means that if the woman ever needs a blood transfusion, no current donor would be a safe match — not even from rare donor banks — except her own previously stored blood.

Why This Discovery Matters

In blood transfusion medicine, matching blood types is critical. Transfusions with mismatched antigens can trigger immune responses that are potentially life-threatening. While ABO and Rh mismatches are the most well-known, rarer antigens can also pose significant risks.

The discovery of Gwada negative could help scientists better understand rare blood compatibility issues and improve care for patients with rare blood types.

Next Steps: Searching for Others

Since blood types are genetic and tend to cluster within populations, the research team plans to begin screening donors in Guadeloupe to see if others share this rare trait.

“Discovering new blood types means offering patients with rare blood a better level of care,” the EFS stated.

The findings also open doors to understanding more about human genetic diversity — and could one day help save the life of someone whose blood type is, so far, truly one of a kind.