“My grandfather died because the report said he had Type-A blood. Unfortunately, it was a Type-O.”

Austrian physician, Karl Landsteiner, first classified the ABO blood types in 1900. Initially, he named the blood groups A, B, and C. In 1910, Landsteiner’s blood group C was renamed to 0 (null). Confusion soon arose between the figure 0, for German ‘null’, and the letter O for ‘ohne’ (meaning without or zero). In a sense, Type-O blood is a typo.

Having a rare blood type is dangerous. About four people per million worldwide, have the Bombay blood group (h/h). They can only accept blood from other people who also have the Bombay phenotype. The rarest blood type in the world is called “golden blood”. Fewer than 50 people worldwide have golden blood— or Rh-null.