Bombay Phenotype (Oh)
Definition
A rare phenotype in which individuals lack functional H antigen on red cells and in secretions due to mutations in FUT1 (and FUT2). Bombay individuals type serologically as group O but produce anti-H antibodies and are incompatible with all ABO-typed blood, including O.
- Genetic cause
- Mutations in FUT1, and often FUT2
- Serological typing
- Types as group O on routine ABO testing
- Antibody produced
- Anti-H, in addition to anti-A and anti-B
- Transfusion compatibility
- Incompatible with all standard ABO groups, including O
Common questions
Why is misidentifying a Bombay phenotype sample as ordinary group O dangerous?+
Ordinary group O blood would be assumed compatible, but Bombay-phenotype individuals carry anti-H and will react against any transfused blood carrying the H antigen, which includes standard O blood. A misclassification in a forensic or clinical typing context can lead to a fatal transfusion reaction if acted on medically.
How is the Bombay phenotype confirmed when standard typing shows group O?+
Testing the serum against a lectin or antiserum specific for the H antigen, such as Ulex europaeus lectin, distinguishes true group O, which carries H antigen and does not react, from the Bombay phenotype, which lacks H antigen and shows a positive anti-H reaction.
Related terms
- ABO Transferase
- A glycosyltransferase enzyme encoded by the ABO gene on chromosome 9. The A allele encodes an enzyme that adds N-acetylgalactosamine to H...
- Forward Grouping (Cell Grouping)
- The direct test of red blood cells with known anti-A and anti-B reagent antibodies to determine which ABO antigens are present on...
- H Antigen
- A fucose-containing oligosaccharide on red cell surfaces and secreted epithelial cells, produced by FUT1 (on red cells) and FUT2 (in secretions). It...
- Reverse Grouping (Serum Grouping)
- Testing a person's serum against known A1 and B reagent red cells to identify which antibodies are present. A healthy adult with...
- Secretor Status
- A genetic trait that determines whether a person expresses their ABO blood group antigens in secreted body fluids such as saliva, semen,...