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A team of scientists found a brand-new blood type in a 68-year-old woman from the French overseas region of Guadeloupe. They announced the finding at the International Society of Blood Transfusion conference in Milan.
How Was This Unknown Blood Type Discovered?
This Guadeloupe native is currently the only known person with the blood type dubbed “Guada negative.” The research team first encountered her in 2011, when she was living in Paris and undergoing routine examinations before surgery. At that time, medical staff could not identify her blood type: it simply didn’t match any known type.
In 2019, scientists re-examined her blood using high-throughput gene sequencing, a method that enables faster, deeper DNA analysis. Over two years, the team sequenced her entire genome, Live Science reported.
The unusual lab results led to the discovery of a mutation in the PIGZ gene, which helps attach certain proteins to the surface of blood cells. That mutation means “she is the only person in the world compatible with herself,” said Thierry Peyrard, a biologist at the French blood service Établissement français du sang (EFS).
What You Need to Know About Blood Types
Human blood type systems are more complex than they seem. They relate to proteins and sugars on the surface of red blood cells called antigens, which the immune system recognizes. Austrian-American biologist Karl Landsteiner identified the first major blood type system—ABO—in 1901 and won the Nobel Prize in 1930.
The classic ABO system shows whether someone has the A and/or B antigens on their blood cells (or neither). The Rh factor system then classifies cells as positive or negative based on the presence of the Rh antigen.
Combined, those systems define eight common blood types, and there are dozens of rarer types beyond them. As of 2024, the International Society of Blood Transfusion (ISBT) recognizes 45 blood group systems. The new “Guada negative” type has been assigned the number 48.
The research team’s next goal is to find out whether anyone else has this characteristic. Because blood type is genetic, the researchers plan to search in Guadeloupe first, focusing on local blood donors.
The EFS said discoveries like this are important because they help ensure patients with rare blood types can receive safe, compatible medical care.
