Hh blood group

The hh blood group, also called the Bombay blood group, is a rare blood type first identified in Bombay (now Mumbai) by Dr. Yeshwant Madhav Bhende in 1952. It is found mostly in the Indian subcontinent, including India, Bangladesh and Pakistan, and in Iran. The phenotype occurs in roughly four people per million worldwide, though its incidence is markedly higher in some areas, reaching about one in ten thousand in Mumbai. People with the hh phenotype lack the H antigen that is the precursor to the A and B antigens of the ABO blood group system, so their blood does not carry standard ABO antigens and they can generally receive transfusions only from other hh donors.