In 1972, when a blood sample was taken from a pregnant woman, doctors noticed it lacked a surface molecule found in all known red blood cells at the time.
After 50 years of research, scientists in the UK have identified a new blood group system thanks to this unusual molecular deficiency.
Louise Tilley, a hematologist from the UK's National Health Service, described the discovery as a significant achievement for providing better care to rare but important patients.
Beyond the well-known ABO and Rh blood group systems, humans have various blood group systems due to diverse proteins and sugars on blood cells.
These antigen molecules help the body recognize harmful substances, and mismatched antigens during transfusions can lead to severe reactions or even death.
Major blood group systems were discovered in the early 20th century, but newly identified groups like the Er system in 2022 affect only a small number of people.
The newly discovered MAL blood group is among these rare systems.
Tilley and her team identified that the missing AnWj antigen in the 1972 case was present in 99.9% of the population.
Named the MAL blood group, individuals with mutations in both copies of the MAL gene have AnWj-negative blood.
The team found three other patients with this rare blood type, though they did not show mutations, suggesting that sometimes blood diseases can suppress the antigen.
The MAL protein plays a crucial role in stabilizing cell membranes and intracellular transport. Previous studies indicated that the AnWj antigen is not present at birth but appears shortly afterward.
With these genetic markers now identified, it will be possible to test whether patients with negative MAL blood types have inherited this trait or if it is due to suppression, which could indicate an underlying medical issue.
While the characteristics of this rare blood group can have devastating effects on patients, understanding such conditions is a critical step toward saving more lives. The findings were published in the journal Blood .
