Weak D antigens are fairly common to which racial group?

• A. Whites
• B. Asians
• C. Hispanics
• D. Blacks

Answer: (D)

Weak D means the D antigen is expressed less intensely on red cells due to variants in the RHD gene. The specific D variants that cause weak or partial D are not distributed evenly across populations; some variants occur more often in certain racial groups. In people of African descent, particular weak/partial D variants are encountered more frequently, so the weak D phenotype is more common in that group. This matters because the presence of a weak D phenotype can affect how blood donors and recipients are classified for Rh typing and transfusion decisions, since some weak D variants may behave differently immunologically.