What Is 'Gwada Negative', the Rarest Blood Group Found in Only One Person on Earth?

After years of research and investigation, scientists have officially identified a new blood type, one so rare, only a single individual on Earth is known to have it. The newly classified blood group, now referred to as ‘Gwada Negative’, was discovered in a 68-year-old woman from Guadeloupe, marking a significant breakthrough in the field of immunohematology.

As of June 2025, the International Society of Blood Transfusion (ISBT) recognises 47 unique blood group systems. With this latest finding by the French Blood Establishment (EFS), Gwada Negative becomes the 48th recognised blood group system, officially accepted by the ISBT.

What Is Gwada Negative?

Gwada Negative is an EMM-negative blood type, identified by the absence of the EMM antigen, a high-incidence antigen found on red blood cells in nearly all humans. The absence of such a universally present antigen is what makes this blood type extraordinarily rare.

The group is named “Gwada Negative,” after the local nickname for the islands of Guadeloupe, where the patient originally hails from. 

How Was It Discovered?

The discovery dates back to 2011, when a 54-year-old woman from Guadeloupe, then living in Paris, underwent routine blood tests before surgery. An unidentified antibody was detected, but due to the technological limitations of the time, researchers could not determine its nature or classify the blood group.

Years later, in 2019, with advances in high-throughput DNA sequencing, researchers at the EFS revisited the case. Their work led to the detection of a mutation in the PIGZ gene, which affects how proteins attach to red blood cells. It was confirmed that the woman had inherited this mutation from both parents, making her the only known person to possess this exact blood group.

“She is the only person in the world who is compatible with herself,” said Thierry Peyrard, the medical biologist who led the study.

Why Is This So Significant?

What makes this discovery even more remarkable is the woman's complete incompatibility with all known blood donors worldwide. Unlike other rare blood groups that may have a handful of known carriers, Gwada Negative has just one—making it the rarest blood type ever recorded.

This uniqueness, however, poses a serious medical challenge. If the woman were to require a blood transfusion, no existing donor would be compatible with her blood, except herself. 

This underscores both the uniqueness and the medical risk of such a rare blood trait.
 

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