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.

Plasma is the liquid portion of blood. About 55% of human blood is plasma; the remaining 45% are RBCs (erythrocytes), WBCs (leukocytes) and platelets (thrombocytes) suspended in the plasma. Plasma is about 92% water.

Blood Group	Antigens	Antibodies	Can give blood (RBC) to	Can receive blood (RBC) from
AB	A and B	None	AB	AB, A, B, O
A	A	B	A and AB	A and O
B	B	A	B and AB	B and O
O	None	A and B	AB, A, B, O	O

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