Bengaluru: The researchers from India and the United Kingdom have identified a new and exceptionally rare human blood group named CRIB, found in a 38-year-old woman from Kolar, near Bengaluru.
The discovery, confirmed after extensive cross-continental analysis, is expected to have significant implications for emergency medicine, pregnancy care, and global blood donation systems.
According to doctors, the woman’s blood did not match any known human blood type, prompting months of intensive research. Despite testing over 20 of her family members, no compatible blood donor could be identified. The rare nature of her blood and its strong reactions to all known samples raised immediate red flags.
Following international collaboration and detailed antigenic profiling, scientists concluded that the woman’s blood was part of an entirely new group – now officially recognized as CRIB, which stands for Chromosome Region IB. The name reflects the blood’s classification under the Cromer blood group system (CR) and its discovery location, India, Bengaluru (IB).
CRIB is not part of the commonly known ABO or Rh systems. Instead, it falls under a newly classified group called INRA (Indian Rare Antigen), which was approved by the International Society of Blood Transfusion (ISBT) in 2022. This makes CRIB one of the rarest blood groups ever documented in medical history.
What makes CRIB especially unique is the absence of a crucial antigen that is almost universally present in human red blood cells. This missing antigen renders conventional transfusions highly dangerous, as the immune system of CRIB individuals may reject even the rarest known blood types.
“This discovery is a game-changer. It exposes how limited our existing donor pools are and highlights the need to expand rare donor registries globally,” said Dr. C. Shivaram, senior haematologist at Manipal Hospital, Bengaluru, who led the Indian team involved in the research.
The CRIB blood group falls under the Cromer system, which includes antigens attached to proteins in red blood cell membranes. While most Cromer antigens are well-documented, the antigen missing in this case was previously unknown, causing the woman’s blood to react negatively to every known donor sample.
The Cromer system plays a critical role in maintaining cell stability and is known for its immunogenic responses during transfusions or pregnancies. People may develop antibodies to Cromer antigens due to:
- Previous blood transfusions
- Pregnancy-related sensitisation
- Inherited genetic mutations
“This woman’s case showed strong antibody responses to all donor samples, which was the first clue that her blood was fundamentally different,” Dr. Shivaram explained.
Medical experts say the CRIB discovery highlights a significant gap in awareness and infrastructure surrounding rare blood types. Current systems are predominantly built around ABO and Rh compatibility, leaving individuals like the Kolar woman vulnerable during emergencies or surgical procedures.
The discovery also raises new questions for maternal-fetal medicine, as rare antigens can pose risks during pregnancy. Antibody formation against unknown blood antigens can lead to complications such as haemolytic disease of the newborn.
As of now, the Bengaluru woman is believed to be the only person on the planet with the CRIB blood group. While her health is stable, doctors caution that in the absence of a compatible donor, any future medical emergency could be fatal.
The CRIB blood group joins a handful of other ultra-rare blood types such as Rh-null, often called “golden blood,” but even those have multiple known donors globally; CRIB currently has only one.
