A novel c.166A>T (p.Thr56Ser) mutation in GYPB*S accounting for unusual S antigen expression.

We found an individual with weakened S antigen expression on red blood cells (RBCs) during routine blood grouping. The proband was typed S+s+ by polyclonal antibodies, but the RBCs demonstrated different reactivity with three monoclonal anti-S. The proband did not have alloanti-S. Cloning and Sanger sequencing revealed that the proband had a c.166A>T (p.Thr56Ser) mutation in exon 4 of GYPB*S. When antibody screening of 60 455 blood donors was performed using the proband RBCs, no antibodies were detected. GYPB*S with c.166T should encode an unusual S antigen but the creation of a novel antigen remains to be investigated.