Blood usually falls into a few widely recognized categories or types, based on the proteins that are expressed on the surface of red blood cells. For example, A or B antigens may be present there, along with Rh factor. But there are some other very rare types of blood, and scientists have now discovered another one.
When a woman in Guadeloupe needed donor blood, clinicians did what they thought was a routine test to determine her blood type. But then they found that her plasma was having a bad reaction to everything they tested, including samples from her siblings. They were unable to find any suitable donor blood, and turned to genetics to learn more about her physiology.
This effort revealed that she carries a mutation in a gene that encodes for an enzyme called PIGZ. The enzyme works to place certain sugar molecules on red blood cell surfaces, except in the case of this individual. Since the enzyme doesn't work as it should, the resulting molecule on the red blood cell surface, or antigen, is slightly altered. This alteration in the red blood cell surface molecule leads to the production of an entirely new blood type, which the researchers called Gwada-negative. (Gwada is a slang term that refers to someone from Guadeloupe, to give the name cultural significance.)
The woman has mild intellectual disability, and has lost two pregnancies, suggesting that there have been some other consequences from her mutation. But they have been mild enough to not attract much attention.
The PIGZ enzyme is known to be related to some neurological processes, and the disruption of this enzyme can lead to issues like stillbirth and neurological disorders.
Blood has to be properly matched before it is given to a person from a donor, or a life-threatening immune reaction can occur. So there will be real challenges to finding a compatible donor for this person, if one even exists.
Lab grown cells may offer a solution for people with extremely rare blood types in the future. Scientists have already been able to generate red blood cells using stem cells, so this process could be modified so that the cells that are produced are tailor made.
Sources: The Conversation, Vox Sanguinis