When we think of blood, we always think of it being red. But did you know that golden blood type also exist? It is world's most rare blood type, known as the golden or Rh-null blood type. Why is it called "golden blood"?Rh antigens in the red blood cells is what causes blood to appear as red, however, people with Rh-null blood lack these Rh antigens, giving the blood a slightly yellow color. The proteins known as Rhesus (Rh) factors or antigens are completely absent in the red cells of people who have golden blood type. Less than 50 people in the world have this type of blood. The Discovery of Golden BloodIn Ancient Greece, it was thought that only gods have golden blood. It was called Ichor, an ethereal fluid, which fabled to have immortal properties, but was toxic to mortals. Then in 1961, a person with "golden blood" in Australia was discovered. This was an Australian Aborginal woman in 1961.The Make-up of Golden BloodOur red blood cells have sugars and proteins which are called antigens. These remain on the surface membranes. Depending on the mix of antigens present, blood is categorized into different blood types and so we have A, B, O, or AB blood types. The ABO system also has a distinction as Rh-positive which decides A+, B+, O+ and AB+ blood type and Rh-negative, which leads to A-, B-, O-, and AB-, this happens due to the presence or absence of "Rh-D" antigen. What is the issue?The biggest issue with golden blood type is that donations of Rh null blood type are incredibly scarce and very difficult to obtain. An Rh null person has to rely on the cooperation of a small network of regular Rh- null donors around the world if they ever need blood. While there are 50 people with the same blood type, only 9 of them are active donors for this blood group. This is what makes the blood type rare and also precious, another reason why it is called the "golden blood". What kind of people have golden blood type?The golden blood type appears to be caused by a genetic mutation (a spontaneous alteration in a gene). It is usually related with mutations in the RHAG gene, which codes for the Rh-associated glycoprotein. This protein is responsible for directing Rh antigens to the RBC membrane.The RHAG mutation is frequently related with hereditary stomatocytosis. These people may experience long-term, moderate hemolytic anemia and accelerated RBC breakdown. The Rh-null phenotype can also be present in certain anemias that people are born with.The following conditions may put you at a higher risk of the golden blood type:Consanguineous marriage (marriage between cousins, brother-sister, or anybody who is a near or distant relative)Autosomal genes (abnormal genes that have disease traits passed down through families)Changes or complete deletion of certain genes, which are RHD and RHCE or RHAGCan people with golden blood type donate blood?Golden blood type can be donated as they have absence of antigens on RBCs, making the person a universal donor. The blood therefore can be donated to anyone with rare blood types within the Rh systems. The blood due to its absence of antigens is great for transfusion and can be accepted by anyone who needs a transfusion without the risk of blood transfusion reaction. However, since the blood type is already rare, it is difficult to find a donor willing to donate it.