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Why is the Rarest Blood Group in The World Named After ‘Bombay’? Here’s The Answer

It is estimated that only 4 per million people have it in the world. However, the incidence of this blood type is slightly higher in, you guessed it, Bombay or Mumbai, where 1 in every 10,000 people are diagnosed with it.

I n 1952 an injured railway worker and a stabbing victim needed a blood transfusion in Mumbai, then Bomnby, but none of the blood types known then worked for them. When their samples were mixed with any of the regular blood types, it coagulated or clumped up.

The doctor trio treating them at the Seth Gordhandas Sunderdas Medical College in the city unsuccessfully tried to match the blood of over 160 donors. After a tireless search effort, they found a resident in the city who suited the blood type of both patients.

Evidently, this wasn’t the regular kind of blood type most people have. And that is how a never before identified blood group was named after one of India’s most famous cities – ‘Bombay Blood Type’ or the HH Blood Type.

Mumbai’s iconic Chhatrapati Shivaji Terminus railway station – Source, Flickr

It is estimated that only 4 per million people have it in the world. However, the incidence of this blood type is slightly higher in, you guessed it, Mumbai, where 1 in every 10,000 people are diagnosed with it.

To understand what makes this blood such an anomaly, a quick recap of grade ten biology is probably handy. 

Here it goes –

Nearly 50 percent of the blood is made of red blood cells (RBCs), one percent is the white blood cells and the rest is plasma.

Now, the RBCs and plasma have protein molecules called antigens and antibodies, respectively. Both very important for a resilient immune system!

RBCs have antigens on their surface, while the plasma or fluid the red and white cells float in, have antibodies in it.

Antigens on the surface of RBCs are either A or B and sometimes have both. The antigens are responsible for blood to be typed A, B, AB and O respectively. If the red blood cells have the antigen A on it, then the plasma has a B antibody and vice-versa.

In the case where the red blood cells have neither A nor B antigen, the plasma has antibodies of A and B, which is the case of the blood type O.

The positive and negative charge comes into play because of another protein called the Rh Factor. If the RBC surface has the Rh, the blood type is positive and if not, negative.

With me so far? This will help you understand why the HH blood is an anomaly.

The cross-talk between the cell and plasma makes each blood type special. This leads to building the immune system, and this is why donor and receiver compatibility is crucial, leading to fatalities if not.

Lesser known fact time – All these blood groups have an overarching antigen H in their blood as well, which is responsible for the generation of A, B, AB, O blood groups.

When people do not have the antigen H in their blood, but only the antibody H, no other blood can be given to them. This low occurrence is the Bombay Blood Group.

They can donate blood to anybody with ABO grouping but can receive blood only from Bombay blood group people.

A problem with the diagnoses in India

Most places where blood type tests are done, the presence & absence of AB and Rh alone is tested in the blood.

Bombay Blood Group does not have A or B antigens and hence can be mistakenly typed as O blood. It is only when a specific test, often unavailable in India, for H antigen is done that it can be differentiated between O and Bombay Blood group. However, the incorrect diagnosis can lead to several complications – including death.

So, what are some of the known causes for the unlikely blood type?

An article published by the Hindu says this phenomenon is mainly because of extensive inbreeding within the same lineage or close-community marriages, such that the ‘blood type’ or the gene pool is significantly restricted.

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The Parsi community, with significant representation in Mumbai, is known for their consanguineous marriages. A high level of consanguinity is present among the parents of the Bombay phenotype.

It is thus likely that the Bombay Blood types have common ancestral origins. People having Bombay phenotype are mostly confined to the Southeast Asia, with India having the highest number of them.

So when Bengaluru based Sankalp India Foundation, a non-government organisation that works primarily in the field of blood donation and thalassemia, a hereditary blood disorder had to send blood to as far as Sri Lanka and Turkey, the reason was less obvious than seemed.

To help patients with the rarest blood type – the Bombay Blood or HH blood group.

Six months ago, a 70-year-old Sri Lankan cancer victim was in dire need of Bombay negative blood.

“In all of Sri Lanka, they couldn’t find a single donor with HH negative group blood type. The family approached Sankalp. We sent blood to her twice, once in December 2016 and the second time in April this year,” said Kumari Ankita to the New Indian Express, a senior volunteer at Sankalp India Foundation.

Bombay negative is rarer than Bombay positive. Sankalp has identified 15 donors for the blood group in India. That’s 15 people in a country of one billion.

Sankalp India Foundation’s September Bombay Blood Drive – Source, website

The foundation has also assisted families in the US and Pakistan to source the blood locally.

In the last seven years, Sankalp has facilitated more than 450 blood transfusions for people with the Bombay blood group.


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While there is no serious state-aided programme that helps people with this blood type, the NGO provides the service free of cost.

“While we pay for the flight cargo charges for poor families, the recipient takes care of shipping charges if he is well-off,” said a volunteer from Sankalp to the New Indian Express.

What to do if you need Bombay Blood Group? Sankalp’s website has the following recommendations – 
– Put up a request for the requirement in the leading newspapers. Please don’t circulate message and emails as it will only contribute to the spam folder.
– Be open to get blood from other cities.
– The most effective way is visiting all blood banks of the city as well as neighbouring big cities.        – Usually, blood banks have a huge list of donors who had donated in the blood bank till date. Out of this huge list, 1 or 2 may be Bombay blood group.
– Get all the family members and relatives of the patients tested for the blood group. It’s very likely that one or the other relative has this group.
To know more, visit Sankalp’s website by clicking here.

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