What is the Bombay Blood Group? Understanding One of the World's Rarest Blood Type

Bombay Blood Group is a very rare blood type that was first found in Mumbai (formerly Bombay), India, in 1952 by Dr. Y. M. Bhende. It is also referred to as the hh blood group or the Bombay phenotype. It is characterized by the total lack of the H antigen on red blood cells, an essential component utilized to construct normal ABO blood group antigens.

Bombay Blood Group: Key Characteristics

Antigen Profile:

Bombay blood group individuals do not have A, B, and H antigens on their red cells. Their plasma has antibodies against all three (anti-A, anti-B, and anti-H) so their blood is different from all other known types.

Prevalence:

It is very rare, about 1 in 10,000 Indians and just 1 in a million worldwide. It is higher in some regions of South Asia because of genetic reasons like close-community marriages.

Genetic Basis:

The Bombay phenotype results from a mutation in the FUT1 gene that codes for the production of the H antigen (fructosyltransferase). Without the H antigen, the body is unable to synthesize the A or B antigens even if the genes for them are present.

Discovery and History

The Bombay blood group was discovered following strange transfusion reactions that occurred in two patients in Mumbai in 1952. The standard blood typing did not work, as neither of the ABO groupings matched. Extensive testing resulted in the identification of a resident of the community who had the rare matching blood group, the first such recorded case.

Source: Differencebetween.com

How Is It Different?

Blood Transfusion Challenges

Bombay blood group individuals are not able to accept any other blood group, even O-type, since all carry the H antigen that causes a dangerous, sometimes life-threatening immune reaction (acute hemolysis).

Risk of Misdiagnosis:

Routine ABO blood grouping tests commonly misclassify Bombay blood group as O type, except if special H antigen testing is carried out. Proper identification is crucial to prevent life-threatening transfusion reactions.

Registry in Blood Bank:

It is essential for individuals with this blood group to be registered with specialized networks and blood banks so rare donors may be found promptly during emergencies.

How is Bombay Blood Group Identified?

Need for specific antigen H testing (not included in routine blood grouping) and reverse grouping to identify the presence of anti-H antibodies, separating it from normal type O.

Clinical Symptoms of Incorrect Transfusion:

Symptoms, when misdiagnosed and administered with normal blood, are fever, backache, and red-brown urine, indicating perilous hemolytic reaction and kidney injury.

Global and Societal Implications

• Increased incidence in South Asia—particularly in Mumbai—due to genetic transmission and local marriage traditions.

• Medical staff need to be educated to identify and screen for Bombay phenotype, particularly in communities where prevalence is more common.

Interesting Facts about Bombay Blood Group

Universal Donor (With a Catch):

Bombay blood group individuals can donate to any other ABO group (as their blood does not contain ABO antigens), but can receive only from their own group.

Named After Its Birthplace:

The fact that the discovery involved Mumbai gave birth to its international name: "Bombay Blood Group".

The Bombay Blood Group (hh phenotype) is a relatively rare but extraordinarily critical aspect of human genetic variability and transfusion medicine. Its recognition, proper diagnosis, and expert blood bank networks are essential for the safety of carriers of this unique blood type.

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