[Rh blood group: Review and importance of genotyping]

Rh antigen is a transmembrane protein whose presence or absence is genetically inherited in humans. The genetic expression is controlled by 2 closely linked genes. The expression of the group (the antigen) can be modified by mutations or deletions in the gene that encodes it, leading to discrepancies that can sometimes only be resolved with molecular testing; such is the case of people with weak or partial expression of the D antigen. Since the antibodies of Rh blood group are not spontaneous and are linked to both the possibility of developing hemolytic disease of the newborn and severe transfusion reactions, the administration of anti-D immunoglobulin has been implemented as a risk reduction measure. In developed countries, genotyping methods are used to guide the administration of this vaccine, since, as a product of human origin, its availability is often not the same in all areas where it is required. Understanding the characteristics that distinguish the antigens of this blood group helps us move toward the use of higher-resolution determination methods that allow us to increase blood safety in our patients.