Bombay Blood Group is extremely rare (1 in 4 million)

• Context (HT): The Bombay blood group is extremely rare.

Blood Groups

• Blood groups are classified based on the presence or absence of specific antigens (chemicals that can induce immune response) on the surface of RBCs.
• Similarly, the plasma of different individuals contains two natural antibodies (proteins produced in response to antigens).
• The four most common blood groups are A, B, AB and O.
  • AB-positive blood type is the universal recipient because AB-positive patients can receive red blood cells from all blood types.
  • Blood donors with type O negative red blood cells are referred to as universal donors, and their red blood cells can be given to any other blood type.

Antigen H

• H antigen is a sugar molecule found on the surface of RBCs and in other bodily secretions.
• It is the precursor to the A and B antigens, the two main antigens determining blood type.
• Depending upon a person’s ABO blood type, the H antigen is converted into either the A antigen, B antigen, or both. If a person has blood group O, the H antigen remains unmodified.

Bombay Blood Group (BBG)

• BBG was first discovered in Mumbai (then Bombay) in 1952.
• Also known as hh, BBG is deficient in expressing H antigen, meaning the RBC has no H antigen.
• The hh blood group is frequently mistaken for the O group, but the key distinction is that the O group possesses the H antigen, whereas the hh group does not.
• Lack of H antigen does not indicate a weak immune system or increased disease susceptibility.
• Their counts for haemoglobin, platelets, WBCs and RBCs are similar to those of other blood types.
• Globally, the hh blood type is rare (1 in 4 million), with a higher occurrence in South Asia.

Concern with BBG: Transfusion Limitations

• The individuals with BBG can only be transfused autologous blood (same blood group).
• Rejection may occur if they receive blood from A, B, AB or O blood group.
• In contrast, the hh blood group can donate blood to ABO blood types.
• This group is rarely stored in blood banks due to its rarity (blood has a shelf life of 35-42 days).
• So, a donor is required very urgently when there is a demand for a BBG patient.

For a detailed study on Blood > Blood | Blood Groups | Formed Elements – PMF IAS