Rhnull: A rare blood group phenotype

Rhnull phenotype is a rare blood group characterized by the lack of expression of all Rh antigens (D, C, c, E and e) on the red cells. The phenotype is further classified into the regulator and amorph type based on underlying genetic defect. The clinical significance of its recognition is that such patients suffer from Rhnull syndrome associated with osmotically fragile red cells called stomatocytes with subsequent chronic haemolytic anaemia of varying degree. Another importance is that such subjects readily form alloantibodies on exposure to Rh antigens. We report herein rare Rhnull phenotype in a young pregnant female which was detected as a part of routine antenatal work-up for red cell antibody screening and identification.