Bombay Blood Group

Bombay blood group is a rare blood group also called Hh blood group. This blood phenotype was first discovered in Bombay, now known as Mumbai, in India, by Dr. Y.M. Bhende in 1952. A patient was admitted to KEM Hospital and required blood transfusions. A sample of blood was sent to the Blood Bank for grouping as is the usual practice. The red cells grouped like O group and hence O group blood was administered. The patient developed haemolytic transfusion reaction, and therefore transfusion had to be stopped.

A detailed study of the patient’s blood revealed a rare genotype (blood group), which was neither ‘A’ nor ‘B’ nor ‘AB’ nor ‘O’. Since the first case was detected in Mumbai (then Bombay), the blood group came to be called as Bombay Blood Group. Blood from a Bombay Blood Group individual only should be transfused to a Bombay Blood Group patient.

Individuals with the rare Bombay phenotype (hh) do not express H antigen (also called substance H), the antigen which is present in blood group O. As a result, they cannot make A antigen (also called substance A) or B antigen (substance B) on their red blood cells, whatever alleles they may have of the A and B blood-group genes, because A antigen and B antigen are made from H antigen; For this reason people who has Bombay phenotype can donate RBCs to any member of the ABO blood group system (unless some other blood factor gene, such as Rhesus, is incompatible), but they cannot receive any member of the ABO blood group system's blood (which always contains one or more of A and B and H antigens), but only from other people who have Bombay phenotype.

This very rare Phenotype is generally present in about 0.0004% (about 4 per million) of the human population, though in some places such as Mumbai (formerly Bombay) locals can have occurrences in as much as 0.01% (1 in 10,000) of inhabitants and 1 in a million people in Europe.

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