What is the D variant antigen in the blood?

For some people, the D antigen (Rh factor) -- a protein with many parts that is found on the surface of red blood cells and that tells your blood type -- may show up only weakly. Red blood cells from these people are known as "D variant." There are two types of D variant antigens:

• "Weak D" means all parts of the D antigen are present but weakly found on the red cell surface.
• "Partial D" means that one or more parts of the D antigen are missing.