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A woman from the French Caribbean territory of Guadeloupe has been confirmed as the only known person in the world to possess a newly classified blood group — now officially recognised as the 48th blood group system.
The new blood group has been named “Gwada negative”, after a local nickname for the islands of Guadeloupe.
The discovery was announced by France’s national blood service, Établissement français du sang (EFS), following its formal recognition by the International Society of Blood Transfusion (ISBT) at its congress in Milan.
The ISBT had previously identified 47 unique blood group systems. This development comes more than a century after Austrian-American biologist Karl Landsteiner first identified the ABO system in 1901, a milestone that would later earn him a Nobel Prize.
How ‘Gwada negative’ was discovered
The woman in question, now 68 years old and living in Paris, first drew the attention of medical researchers in 2011. At the time, she was undergoing routine pre-surgical blood tests.
Initial laboratory tests failed to classify her blood using any known blood typing methods. An atypical antibody was identified, and her blood could not be matched within existing systems.
A “very unusual” antibody was first found in the patient in 2011, Thierry Peyrard, a medical biologist from EFS, who has played a key role in the study, told AFP.
However, at the time of the initial tests, the tools and technology available were insufficient to explore the anomaly further.
The case remained unexplained for nearly eight years, until 2019, when scientists at EFS returned to her sample using a more advanced diagnostic tool — high-throughput DNA sequencing.
This technology enabled researchers to conduct a deeper genetic investigation, ultimately revealing a mutation in the PIGZ gene, which alters how specific proteins anchor themselves to red blood cells.
The woman was confirmed to have inherited the condition from both her parents, who each carried a version of the mutated gene. This made her the only known person on Earth to have this specific blood group.
“She is the only person in the world who is compatible with herself,” said Peyrard.
He noted that the name “Gwada negative” was chosen in reference to the patient’s Guadeloupean origin and also because “it sounds good in all languages,” making it a suitable term for global usage among the scientific and medical communities.
What makes blood types so complex
Though most people know their blood type as A, B, AB, or O — combined with a positive or negative Rh factor — these are just the best-known components of a vast and intricate system.
Human red blood cells carry more than 600 different antigens, and each unique combination of these can result in a new blood type.
For this reason, the ISBT recognises blood group systems rather than individual blood types. Each system is defined by the genetic and serological properties that influence the expression of antigens.
The ABO and Rh systems are the most clinically important, especially for transfusions, but over the years, dozens of others have been identified, including rare ones that affect transfusion compatibility and immune response.
The addition of Gwada negative follows previous rare group discoveries such as the “Er” system, which was recognised in 2022.
Scientific progress in gene sequencing, particularly high-throughput genomic tools, has accelerated the pace of discovery in recent years. According to experts, more new blood groups may be identified annually as sequencing technologies become more widespread and affordable.
What this means for rare blood group carriers
Understanding blood types is critical in transfusion medicine. When blood from a donor carries antigens that are not recognised by the recipient’s immune system, it can trigger a dangerous immune reaction, which can be life-threatening.
The ABO-Rh system offers transfusion compatibility in 99.8 per cent of cases, but patients with rarer blood types face greater risk and more limited donor options.
The EFS highlighted this point in its public statement: “Discovering new blood groups means offering patients with rare blood types a better level of care.”
Although millions of theoretical blood types are possible based on antigen variation, only 48 blood group systems have met the rigorous genetic and serological criteria to be recognised by the ISBT.
Every addition to this list not only advances the scientific understanding of human genetics but also enhances the safety and efficacy of transfusions for rare cases.
In the United States alone, the Centers for Disease Control and Prevention (CDC) reports that more than 14 million units of blood are transfused annually. Accurate typing and identification are essential to ensure those transfusions are both safe and effective.
Why this puts the woman with ‘Gwada negative’ in a unique position
The woman with Gwada negative blood is unique in more ways than one.
Unlike other rare blood types that may have small numbers of known carriers, she is the only confirmed person worldwide with this classification, making her completely incompatible with any blood donor currently known to science — except herself.
This reality poses major challenges should she ever require a transfusion. Her genome sequencing has been archived, and researchers are now focused on locating other potential carriers, particularly among blood donors from Guadeloupe and surrounding regions.
Because blood types are inherited, populations with shared ancestry may be the most likely sources of other cases.
The blood group’s formal recognition by the ISBT not only gives it a place in global transfusion protocols, but also encourages international collaboration to identify other carriers and develop strategies for rare donor recruitment.
With inputs from agencies