A+, AB, O- … but have you heard about Bombay Blood Group? 
Bombay blood group is the rarest blood group. First found in Bombay (Mumbai) in India, hence called Bombay blood group. It is observed to occur in 1 out of every 250,000 people except in parts of India where the incidence has been observed to be as much as 1 in every 7,600. It is also called the HH group. The peculiarity is that they do not express the H antigen. As a result they cannot form A antigens or B antigens on their red blood cells. Thus they can donate blood to anybody with ABO grouping but can receive blood only from Bombay blood group people.
What is Bombay blood group?
To understand Bombay blood group we must understand the details of blood grouping. When we say someone has blood group A, it means that the person has antigen of type 'A' and antibody of type 'B' in his/her blood. People with AB have both antigen A and B in their blood and no antibodies. People with O blood group have only antibodies A and B and no antigens. However what is not generally known is that all these groups have an antigen H in the blood as well. There are very few people who do not have this antigen H also in their blood. Instead they have antibody H because of which no other blood can be given to them.
Blood Groups(Antigens and Antibodies)
Why are Bombay group people generally tested as O?
Most places where blood test is done, the presence and absence of AB and Rh alone is tested in the blood. Since Bombay group does not have neither A nor B antigens, it is usually read as O blood group. It is only when a specific test for H antigen is done that one can differentiate between O and Bombay Blood group.
There are less than five sri lankans who having Bombay Blood group
References:
http://en.wikipedia.org/wiki/Hh_blood_group
http://www.sankalpindia.net/drupal/book/bombay-blood-group
http://www.cure2children.org/content/ab-o-%E2%80%A6-have-you-heard-about-bombay-blood-group
Bombay blood group is the rarest blood group. First found in Bombay (Mumbai) in India, hence called Bombay blood group. It is observed to occur in 1 out of every 250,000 people except in parts of India where the incidence has been observed to be as much as 1 in every 7,600. It is also called the HH group. The peculiarity is that they do not express the H antigen. As a result they cannot form A antigens or B antigens on their red blood cells. Thus they can donate blood to anybody with ABO grouping but can receive blood only from Bombay blood group people.
What is Bombay blood group?
To understand Bombay blood group we must understand the details of blood grouping. When we say someone has blood group A, it means that the person has antigen of type 'A' and antibody of type 'B' in his/her blood. People with AB have both antigen A and B in their blood and no antibodies. People with O blood group have only antibodies A and B and no antigens. However what is not generally known is that all these groups have an antigen H in the blood as well. There are very few people who do not have this antigen H also in their blood. Instead they have antibody H because of which no other blood can be given to them.
Blood Groups(Antigens and Antibodies)
Why are Bombay group people generally tested as O?
Most places where blood test is done, the presence and absence of AB and Rh alone is tested in the blood. Since Bombay group does not have neither A nor B antigens, it is usually read as O blood group. It is only when a specific test for H antigen is done that one can differentiate between O and Bombay Blood group.
There are less than five sri lankans who having Bombay Blood group
References:
http://en.wikipedia.org/wiki/Hh_blood_group
http://www.sankalpindia.net/drupal/book/bombay-blood-group
http://www.cure2children.org/content/ab-o-%E2%80%A6-have-you-heard-about-bombay-blood-group
