I first heard of the “Bombay blood group” while watching the movie Kahaani, starring Vidya Balan. The name caught me off guard, and I wanted to dive deeper into the science behind it.
What is it?
· The Bombay blood group ( h/h phenotype) is an extremely rare blood type.
· Discovered by Dr. Y.M. Bhende in 1952 in Bombay (now Mumbai).
· It is most frequently mistaken for Type O blood due to the absence of antigen A & B.
However, there is a hidden difference: while Type O blood contains the H antigen, Bombay blood does not.
The Genetics: The FUT1 Gene 
While most of us focus on the ABO gene, the FUT1 gene plays a silent but critical role.
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The Dominant H allele which produces the H antigen—the essential precursor required to build A and B antigens.
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The Recessive h allele: The Bombay phenotype is an autosomal recessive trait. It occurs when an individual inherits two recessive copies of this gene (h/h).
Because these individuals lack the H antigen, they cannot produce A or B antigens.
Prevalence of Bombay blood group
In India: roughly 1 in 10,000 people, in Taiwan: roughly 1 in 8,000 people & in Europe: Extremely rare, affecting only 1 in 1,000,000 people.
Challenges
The biggest challenge for those with Bombay blood is blood transfusion. Because their bodies lack A, B & H antigens, their immune system produces anti-A, anti-B & anti-H antibodies. This means they cannot receive blood from Type A, B, AB, or even Type O donors. They can only receive blood from another person with the Bombay phenotype
Knowing now that Type O can actually be fatal for someone with the Bombay phenotype, do you think rare blood type screening should be more common in routine checkups?
MBH/PS
