What is bombay blood group?

Bombay Blood Group (hh)

The Bombay blood group, also known as the hh blood group, is a rare blood type. Individuals with this phenotype do not express the <a href="https://www.wikiwhat.page/kavramlar/H%20antigen">H antigen</a>, which is the precursor to the A and B antigens. Consequently, they also lack A and B antigens on their red blood cells.

Key Characteristics:

• Absence of H, A, and B antigens: Red blood cells lack the H antigen, which is usually present in blood types A, B, AB, and O. Therefore, A and B antigens are also absent.
• Anti-H antibodies: Individuals with the Bombay phenotype produce potent <a href="https://www.wikiwhat.page/kavramlar/Anti-H%20antibodies">Anti-H antibodies</a> in their serum. This is crucial because these antibodies will react with almost all red blood cells (except those of other Bombay phenotype individuals).
• "O" phenotype appearance: In routine blood typing tests, Bombay blood may initially be misidentified as blood type O because it lacks A and B antigens. However, unlike type O individuals, Bombay blood contains anti-H antibodies.
• Transfusion incompatibility: Individuals with Bombay blood can only receive blood from other individuals with the <a href="https://www.wikiwhat.page/kavramlar/Bombay%20phenotype">Bombay phenotype</a>. Transfusion with blood from A, B, AB, or O blood types would result in a severe transfusion reaction due to the anti-H antibodies.
• Genetic Basis: The Bombay phenotype results from a mutation in the <a href="https://www.wikiwhat.page/kavramlar/FUT1%20gene">FUT1 gene</a> (also known as H gene), which prevents the production of the functional H enzyme (fucosyltransferase). This enzyme is responsible for adding fucose to the precursor oligosaccharide, forming the H antigen. Another gene, <a href="https://www.wikiwhat.page/kavramlar/FUT2%20gene">FUT2 gene</a>, can also affect H antigen expression in secretions, but FUT1 is more relevant to the Bombay phenotype on red blood cells.
• Inheritance: The condition is inherited in an <a href="https://www.wikiwhat.page/kavramlar/Autosomal%20recessive">Autosomal recessive</a> manner. This means that an individual must inherit two copies of the mutated FUT1 gene (one from each parent) to express the Bombay phenotype.
• Rarity: The Bombay blood group is very rare, with a higher prevalence in certain regions, such as Mumbai (formerly Bombay), India, where it was first discovered.

Implications:

• Blood transfusions: Careful blood typing and screening are essential to identify individuals with the Bombay phenotype to ensure they receive compatible blood.
• Genetic counseling: Individuals who are known carriers of the mutated FUT1 gene may seek genetic counseling to understand the risk of having children with the Bombay phenotype.