Step aside A, B, and O—there’s a new player in town. Scientists in France have just reported the discovery of a novel, rare blood type, only recorded in a single person to date.

The French Blood Establishment (EFS), the country’s sole civilian blood transfusion organization, announced the discovery over the weekend. The blood type, nicknamed “Gwada negative,” was found in a French woman originally from Guadeloupe. It’s the 48th distinct blood group system to be established.

“This discovery was officially recognized in early June in Milan by the International Society of Blood Transfusion,” the EFS said in a statement released on LinkedIn Friday.

It’s taken a long while for this recognition to happen. Researchers at the EFS first noticed an unusual antibody in the woman’s blood in 2011, after she provided a sample for routine examination before a surgery in her early 50s. But they simply didn’t have the resources or technology needed at the time to look further into it. Finally, in 2019, they were able to perform “high-throughput DNA sequencing” of the woman’s genetics, which confirmed she possessed a unique blood-related mutation inherited from both her parents.

Her blood type appears to be the result of having both copies of this mutation, since her siblings have one copy and don’t have it. The blood type is formally called PIGZ, with Gwada negative being a reference to the woman’s Guadeloupean origin (Guadeloupe is an French island region in the Caribbean). So far, she seems to be one of a kind.

“She is the only person in the world who is compatible with herself,” Thierry Peyrard, a medical biologist at the EFS who helped discover the blood type, told the AFP.

Blood types refer to the particular combinations of antigens that cover our red blood cells. The most commonly found antigens belong to the ABO blood group, but scientists have discovered over 600 separate antigens that can be sorted into dozens of blood groups. Knowing our blood type is important, since our body’s immune system can generate antibodies that attack blood cells from someone with a blood type incompatible with ours. This not only complicates blood donation but pregnancy. So aside from simple curiosity, categorizing Gwada negative and other rare blood types can be medically vital.

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

Peyrard and his colleagues are now hoping to find others with the woman’s blood type, and will first plan to look for it among blood donors in Guadeloupe.