Rarest Blood Type and Uncommon Blood Groups in Humans

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Rarest Blood Type in the World

The rarest blood type in the world using the ABO and Rh system is The RH Null blood type. Someones blood is grouped as Rh-null if the blood lacks all of the 61 possible antigens of the rhesus system. This type of blood can be considered as the Golden blood if not more as it is even rarer than gold. As rare as the blood type is, it is dangerous to have this type of blood because when such a person needs blood, the possibility of getting a donor is null or rarely possible. The Rh-null blood type is so rare that less than 50 people have been reported to have it worldwide. The blood type was first discovered in an Aboriginal Australian woman.

The AB-negative blood was initially seen as the rarest blood type and still been seen as such by some as the Rh-null is so rare that some may see it as insignificant to be included as a blood type.

Uncommon Blood Types in the World

There are so many blood group types in the world but the commonest (ABO and Rhesus) are the ones often discussed leaving out the other systems of blood types. The list of blood group types are so many that naming and discussing all blood types may not be possible. The reason for this article is to discuss the rarest blood type in the world and also discuss the uncommon blood group systems other than the ABO and RH systems. These uncommon blood group systems are less frequently of clinical importance that is the reason why they are not often discussed. Although naturally occurring antibodies of the P, Lewis and MN system are not uncommon, they usually only react at low temperatures and hence are of no clinical consequence. Also, the immune antibodies against antigens of these systems are detected infrequently. Many of the antigens are of low antigenicity and others such as the Kell are of relatively low frequency and therefore provide few opportunities for iso-immunization except in multiply transfused patients.

The list below shows how the red cell antigen groups are presented in order of clinical importance. The abbreviations next to the names are the symbols each system represents. Many red cell antigens have an interesting but inconsistent approach to nomenclature. However, because these (as well as the platelet antigens) are commonly used, they are used along with the nomenclature proposed by the International Society of Blood Transfusion (ISBT).

International Society of Blood Transfusion Terminology

The ISBT Working Party on Terminology for Red Cell Surface Antigens was established in 1980 with the goal of creating a uniform nomenclature. Blood antigens were categorized into systems, collections, and series. The list below shows the 24 plus (ABO and RH) systems by the ISBT.

List of the uncommon blood types in the world

  1. MNS (MNS)
  2. P (P1)
  3. Lutheran (LU)
  4. Kell (KEL)
  5. Lewis (LE)
  6. Duffy (FY)
  7. Kidd (JK)
  8. Diego (DI)
  9. Cartwright (Yt)
  10. Xg (XG)
  11. Scianna (SC)
  12. Dombrock (DO)
  13. Colton (CO)
  14. Landsteiner-Wiener (LW)
  15. Chido/Rodgers (CH/RG)
  16. Hh (H)
  17. Kx (XK)
  18. Gerbich (GE)
  19. Cromer (CROM)
  20. Knops (KN)
  21. Indian (IN)
  22. Ok (OK)
  23. Raph (RAPH)
  24. John Milton Hagen (JMH)

In humans, the above 24 plus the ABO and RH makes the 26 blood group systems recognized by the International Society of Blood Transfusion Terminology each system is based on the 228 antigens identified on the red blood cells. Additional antigens have been identified but have not been assigned to established systems. These Red blood cell antigens may be proteins, glycoproteins, or glycolipids; most of the red cell antigens are synthesized by the red blood cells but some antigens, such as those of the Lewis and Chido/Rogers systems are adsorbed onto the red cell membrane from the plasma. Some red cell antigens are specifically found on red cells only while others are found on other cells throughout the body.

The above blood group even though uncommon, they are capable of producing blood transfusion reactions, for this reason, a crossmatch test represents an important measure in the avoidance of transfusion problems. Before a planned blood transfusion is done, the serum from a recipient is mixed with red blood cells from the prospective donor; while serum from the prospective donor is mixed with red blood cells from the prospective recipient. In order to ensure no reaction occurs following blood transfusion, there should be no agglutination present in either mixture.

Some potentially dangerous serum antibodies may bind to the erythrocytes leading to opsonization, but not necessarily inducing agglutination; in order to check for the presence of these antibodies, anti-human immunoglobulin serum is added and should it crosslink such antibodies agglutination will result.

Each of these blood group systems will be discussed as separate articles.

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