Rh null blood type, also known as Rhesus null, is one of the rarest bloods in the world. Its properties make “golden blood” a precious fluid, but can also be a source of concern for the wearer.
What is the Rh null blood group?
Before discussing the Rhesus null group, we need to understand what a blood group is. “In humans, we currently know 44 blood groups, also called blood group families or systems, the best known of which is the ABO system“, explains Thierry Peyrard, medical biologist and director of the National Reference Department in immuno-hematology and rare blood at the French Blood Establishment. Another major system is the RH or Rhesus system. Within these different families of blood groups, we find what are called antigens, molecules present or absent on the surface of blood cells. For the record, an antigen is a substance capable of generating antibodies in a situation of incompatibility. “In the Rh system, we count 56 different antigens, positive or negative, depending on the individual. When a person is Rh negative, they are missing an antigen called D. About 15% of the population in Europe is Rh negative, in other words D negative, which is therefore not rare at all”, would like to remind Thierry Peyrard. On the other hand, when a person is Rh null“all Rhesus system antigens are absent on the surface of red blood cells. This blood group is extremely rare, as we have a few dozen Rhesus null individuals in the world, for about ten more or less active blood donors worldwide. In France, in 18 years of career, we found 3 Rhesus null groups, including one in Belgium, confesses the biologist. And these people were part of the patient circuit, so we never found any new Rhesus null donors.” “We call the blood group Rhesus null “golden blood”, because it is the universal blood for all rare blood groups of the Rh system. There are indeed many other rare blood groups affiliated with the Rhesus family, much less rare than Rhesus null. For example, the RH:-18 group is rare and is found mainly in populations from sub-Saharan Africa, but we have very few donors. This rare group is also found in some patients with sickle cell disease. These patients must, if they are immunized with an anti-RH18 antibody, be transfused with the same rare blood as theirs, or with Rh null blood insofar as the latter can be considered universal.explains the biologist.
What are the consequences for a person carrying this blood type?
Rhesus null blood group is easily detectable in a routine check-up or during pregnancy. “For the other rare blood groups, more than 190 are known in humans, we do not systematically search for them but if the antibody corresponding to the rare group is present, routine check-ups before hospitalization or during pregnancy monitoring are an indirect way to easily highlight them. In a Rhesus null person, there is no risk at the first blood transfusion (in the absence of prior pregnancy), because the immune system has not yet been stimulated. The cells of the immune system must be given time to activate. The risk begins to appear at the second transfusion or during the second pregnancy). If the individual is immunethat is to say that the organism has produced the antibody corresponding to its rare blood group, then it is imperative to donate compatible blood. This is when we call on the Rare Blood Bank, indicates the director of the National Reference Department in Immunohematology and Rare Blood. And to continue:before any transfusion, we carry out an RAI (Search for Irregular Antibodies). This allows us to know if the patient has antibodies directed against the red blood cells of blood donors which would be used to transfuse him”. Exceptionally, a rare blood group can be associated with a pathology, but not the Rh null group. People in this group are not sick, although they have fragility in the red blood cells compared to the general population. Indeed, Rhesus proteins have a role in stabilizing the membrane of the red blood cell. On average, a red blood cell has a lifespan of 120 days. In a subject of the Rh null group, it is shorter. Nevertheless, their bone marrow manages to compensate for this slight deficit. Consequently, their hemoglobin level is a little lower than average, but without being pathological.
Is it the rarest blood type in the world?
According to Thierry Peyrard, “golden blood” is very rare, but it is not necessarily the rarest in the world. Concerning the Rhesus null group, we count approximately 1 case in 10 million people. Nevertheless, the French Blood Establishment knows patients or families of patients with other blood group types that are sometimes unique in the world, found in a single individual or only in siblings.
Is it compatible with all other blood groups?
What makes this blood particularly attractive is the fact that it is considered universal. Rhesus null group is compatible with all rare Rhesus blood groups. “Golden blood” is therefore very valuable: in practice, it can respond to many transfusion problems encountered in particular in patients suffering from sickle cell disease with a rare blood type of the Rhesus system. “Only one active Rhesus null donor is listed in the databases in France, even if he lives in Switzerland. This donor comes to give his blood at the border, then the bags are transferred to Paris to be frozen at the National Rare Blood Bank. To preserve all the red blood cells, freezing is done at -80°C and is reserved for rare blood because of the high cost of such long-term preservation.“, specifies Thierry Peyrard.
France knows how to manage its rare blood stocks independently
What is the care of a carrier of Rh null blood group?
Rhesus null blood is reserved for people of the same group immunized with the corresponding antibody, who have already been transfused or who have had pregnancies. Indeed, in the event of haemorrhage or surgical intervention, giving the same blood to the patient, i.e. Rh null, is imperative. “We can also run international aid thanks to the rare blood network. We may need to contact our colleagues, but in almost all cases (more than 99.9% of situations), France knows how to manage its stocks of rare blood independently. If a call is made from another country, we will of course help, if we have a certain degree of comfort, always making sure to preserve our stocks. In case of emergency, we can quickly send a donation internationally thanks to important logistical means“.”When a rare blood type is found in someone, we encourage him to donate his blood to supply the National Rare Blood Bank and we offer his siblings to be tested. From a genetic point of view, there is a one in four chance of finding this same rare group in a sibling. Communicating the existence of a rare blood group to a patient or a blood donor is a delicate process: indeed, not all people will react in the same way. Either they are anxious about having health problems or traveling if they need a transfusion, or they see their rarity as a unique advantage for the benefit of patients with the same rare group as theirs. In all cases, the national reference laboratory is there to provide educational support anyone who wishes to obtain information on their rare blood type“, wishes to recall the medical biologist Thierry Peyrard.
Thanks to Thierry Peyrard, medical biologist and director of the National Reference Department in Immunohematology and Rare Blood at the French Blood Establishment.
Sources:
– All about transfusion
– French Blood Establishment