Partial D
It is important to differentiate weak D (due to a quantitative difference in the D antigen) from partial D (due to a qualitative difference in the D antigen). Simply put, the weak D phenotype is due to a reduced number of D antigens on a red blood cell. In contrast, the partial D phenotype is due to an alteration in D-epitopes. Thus, in partial D, the number of D antigens is not reduced but the protein structure is altered. These individuals, if alloimmunized to D, can produce an anti-D antibody. Therefore, partial D patients who are donating blood should be labeled as D-positive but, if receiving blood, they should be labeled as D-negative and receive D-negative units.
In the past, partial D was called 'D mosaic' or 'D variant.' Different partial D phenotypes are defined by different D epitopes on the outer surface of the red blood cell membrane. More than 30 different partial D phenotypes have been described.
Read more about this topic: Rh Blood Group System
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