Only 1 in 10,000 people on the Indian subcontinent and 1 in 4 million people worldwide have the Bombay phenotype.

The only blood types that the average person is aware of are A+, A-, B+, B-, AB+, AB-, and O+ and O-. Whenever you go for a blood test, you expect one of these eight in the results. However, there is a small chance that your results will show none of these but a blood type known as the Bombay Blood Group. And if you do have this group, you are a part of one of the most rare blood types in the world.

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Bombay Blood Group and its history

In 1952, a patient was admitted to KEM Hospital in Mumbai. As a normal procedure, the patient’s blood was tested which showed an absence of the A and B antigens. This indicated that it was neither A nor B blood type. The absence of the A and B antigens and the presence of the Rh antigen convinced the doctors that it was an O+ blood type. But when they tried transfusing the patient’s blood with O+ blood at the hospital’s blood bank, it did not match. Nor did it with any other blood type. After further tests, Dr Y M Bhende found that the patient’s blood was a new blood type and named it after the place where it was discovered, Bombay (present-day Mumbai).

A detailed study on the type revealed a new blood character called the H antigen which acts as a precursor to the antigens of the ABO blood groups. The absence of the antigen H signifies the presence of the Bombay phenotype. Therefore, to detect a person with the Bombay blood group, a separate H antigen test is required.

Like other blood groups, the Bombay phenotype also has its negative and positive components in the Rh (Rhesus) system. If the blood shows an absence of the H antigen and the presence of the Rh antigen, it is called Bombay Rh-positive. If it does not have either of the antigens, it is called Bombay Rh-negative.

One of the rarest blood groups

Figures estimate that only 1 in 10,000 people have the Bombay blood type in the Indian subcontinent. The number drops to 1 in 4 million when we take into account the global population.

Vinay Shetty, who runs an NGO that maintains a registry of Bombay blood donors, says that the number is much lower than estimated. According to him, only 500 Bombay Rh-positive people and 30-35 Bombay Rh-negative people are found in India. This might be due to a lack of proper blood testing (H antigen tests) on people with the O blood type, who possibly might be carrying the Bombay phenotype.

Challenges

“The biggest challenge for people with Bombay blood type is the question: when I need blood, will I get it?” Shetty says.

Among the few Bombay blood donors in the country, most of them are Bombay Rh-positive. There are only a countable number of Bombay Rh-negative donors in India and the world. Shetty notes that it is easier when his company is contacted and asked for Bombay Rh-positive blood. However, things get complicated when a request for Bombay Rh-negative is received.

“Finding a Bombay Rh-negative donor in an emergency is almost impossible,” he admits. “Finding nearby matching donors in times of need is one of the biggest obstacles faced by people with the Bombay blood type.”

The logistics of carrying such a rare blood type from the donor to the patient are also quite challenging. The blood is required to be stored at specific cold temperatures. Maintaining this cold chain is difficult and expensive. Add to that the cost of air freight if the blood has to be transported urgently to a faraway place.

Non-profit organizations like Think Foundation and Sankalp India Foundation have contributed immensely to offset these challenges. These NGOs keep a registry of Bombay Blood Group donors across the country. Whenever the need for blood type arises, these organizations are contacted. They connect a nearby donor with the hospital that requires the blood and also take care of the logistics if needed.