Bombayfenotypen

The Bombay phenotype is a rare human blood group that is a variant of the ABO blood group system. Individuals with the Bombay phenotype do not express the H antigen, which is a precursor to the A and B antigens. This means that regardless of their ABO genotype, their red blood cells do not have A or B antigens on their surface. Consequently, they appear to have the blood type O. However, they possess antibodies against both A and B antigens, as well as antibodies against the H antigen itself.

The Bombay phenotype is caused by mutations in the FUT1 gene, which is responsible for producing the H antigen. Without a functional FUT1 gene, the H antigen cannot be produced, and therefore the A and B antigens cannot be formed. This condition is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to exhibit the phenotype.

Because individuals with the Bombay phenotype have anti-H antibodies, they can only receive blood transfusions from other individuals with the Bombay phenotype. This makes finding compatible donors extremely difficult. They can donate blood to anyone who is of the Bombay phenotype, as their red blood cells lack A, B, and H antigens. The prevalence of the Bombay phenotype is very low, estimated to be around 1 in 10,000 in India and 1 in a million in Western populations.