The Rh blood group system: RHCE update.

While the previous review encompassed the Rh blood group system (Chou ST, Westhoff CM. The Rh and RhAG blood group systems. Immunohematology. 2010;26:178-86), this update focusses on the RHCE gene and its variants. Four new antigens- PARG, CEVF, CEWA, and CETW (RH60 to RH63)-were reported since the last update. RHCE*cEMI (RHCE*03.31) was amended from a null allele to an allele encoding very weak antigen expression. The following topics are discussed: cross-reactive alleles [such as RHCE*ceHAR (*01.22.01) and RHCE*ceCF (*01.20.06) which may type D+ with some monoclonal anti-D reagents], issues with hybrid alleles and allele dropout, common haplotypes (association between RHCE alleles and specific RHD alleles), and clinical considerations. While the detailed description of new Rh antigens has become rare, many RHCE alleles have been reported since the previous review, a result of increased adoption of DNAbased testing for red blood cell antigens in immunohematology laboratories. The Rh blood group system has fascinated generations of immunohematologists and is likely to continue to do so for decades to come.