Figure 1: The genetic background for different RhD types (simplified). D negative Caucasians most often have a complete RHD gene deletion, but Africans and Asians have often an inactive RHD. The partial D red blood cells (RBC) demonstrate a normal number of Rh D antigens but with altered D epitopes. Many partial D results from hybrid genes with portions of RHD replaced by the corresponding portions of RHCE. The weak D red blood cells have a reduced number of complete D antigens. Weak D types primarily results from single point mutations in RHD. Some partial D (the most common in Caucasians: DVI) show both weak D and partial D features.