Bombay Blood Group!!! Does that ring bell? Must have heard in the movie “Kahaani”. Bombay blood group is a rare blood type which was named after Mumbai where it was first discovered on 1952 by Dr.Bhende.
The red blood cells of individuals possessing Bombay blood group lack A and B antigens but were found to possess another antigen that was unknown earlier.
The phenotype of Bombay blood group is HH. H antigen is precursor for formation of A and B antigen. The biosynthesis of H antigen requires an enzyme glycosyl transferase which assists in formation of oligosaccharide chains of antigens A and B. The resulting oligosaccharide chains are attached to lipids and proteins. But since RBCs of people possessing Bombay blood group do not have H antigen, antigen A and B are not formed. The cause of Bombay blood group phenotype is mutation in H genes on chromosome19 which causes a nonfunctional H glycosyl transferase. The gene is Mendelian recessive gene. A mutation that changes the code for trypsin at amino acid residue 316 of the transferase to that for a stop codon. Depending upon a person's ABO blood type, the H antigen is converted into either the A antigen, B antigen, or both. If a person has group O blood, the H antigen remains unmodified. Therefore, the H antigen is present more in blood type O and less in blood type AB. Bombay blood group is inherited because of two recessive alleles of H antigen by both parents of person.
As there are no surface antigens on RBCs, people with HH group can donate blood to people possessing A, B and O blood groups; provided the Rhesus factor is compatible.
However, they cannot receive blood from A, B and O blood type. In cases of emergency when blood transfer is required for patients possessing Bombay blood group, it is important to detect their phenotype because the usual test for ABO blood group system would show them as blood O since they do not possess A or B antigen. Receiving blood from other blood type causes transfusion incompatibilities.
About 4 people in a million may possess Bombay blood group overall the globe ,however in some places such as Mumbai locals can have occurrences in as much as 1 in 10,000. Given that this condition is very rare, any person with this blood group who needs an urgent blood transfusion will probably be unable to get it, as no blood bank would have any in stock. Those anticipating the need for blood transfusion may bank blood for their own use, but of course this option is not available in cases of accidental injury since the preservation of blood doesn't last more than 40 days.
What to do if you need Bombay Blood Group
One should start a search for Bombay blood group by following these steps.
Few leading Hospital like King Edward Memorial Hospital (Contact- 022-2413 6051), Mumbai and few online blood donors database like www.lionsbloodline.com have registered donors who can be contacted during emergency.