Null RH and Golden Blood |  What is the rarest blood type?

Blood banks often report low stocks of some hard-to-find blood types, such as O- and AB-. However, these types become common—in fact, very common—near Rh Null, that is, blood from people that is neither positive nor negative. It was so rare that he earned the nickname “Golden Blood”.

In a 2010 survey, only 43 people had been diagnosed with the world’s rarest blood type, Rh Null. In fact, some of these individuals are Brazilians. The consensus is that this blood type is transmitted between families, and when one case is discovered, others tend to appear in the same family.

Patients who are Rh Null, also known as Golden blood, have the rarest blood type in the world (Image: ANIRUDH/Unsplash)

In science, the first record of Golden Blood dates back to 1961. Doctors and scientists confirmed the existence of Rh Null in an Australian woman, when she was undergoing a medical procedure. Until then, it was believed to be impossible for anyone to live with the condition.

People with the rarest blood type face numerous difficulties throughout their lives, as the number of possible blood donors is really low. Second article in the magazine FAPESP Researchthese individuals usually have a mild but chronic type of anemia.

What does it mean to have “Golden Blood”?

To understand what it means to have Golden Blood, you need to know that what differentiates known blood types are the antigens — molecules that can trigger the production of antibodies — present on the surface of red blood cells (red blood cells). 342 blood-associated antigens are known and, based on them or their absence, it is defined whether someone is AB+ or A-, for example.

In the case of Rh Null, the classification of the Rh Factor comes into play. In this case, about 61 antigens are considered to define whether someone is type positive or negative. Among them, the best known is RhD, which is associated with the positive group. Meanwhile, Rh negative people do not have this specific protein, but red blood cells are considered normal.

Rh Null type red blood cells do not have Rh Factor antigens (Image: Claudioventrella/envato)

Now, in the case of Rh Null, it is possible to identify the absence of the RhD antigen, but the other antigens of the Rh system are also not present in the red blood cells. It is these absences that make these individuals so rare and also make them generally have more fragile red blood cells.

Rh Null blood donation

Because of compatibility issues, people with Rh Null blood type can only receive blood donations that are the same as their own, which makes transfusions virtually impossible. Faced with this type of limitation, patients who know about their condition usually keep reserves of their own blood, in case of a medical emergency.

On the other hand, this blood type can be considered the true universal blood, as it can be received by anyone else due to its lack of antigens, when considering the Rh Factor. However, there must also be compatibility with the ABO System for the donation to be safe.

Source: FAPESP Research, Pro-Blood and Mosaic Science

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