RESUMO
BACKGROUND: The Dombrock (Do) blood group system consists of six distinct antigens: Do(a) , Do(b) , Gy(a) , Hy, Jo(a) , and DOYA. Our finding of a pregnant patient whose red blood cells (RBCs) were Hy+ but whose serum contained an apparent alloanti-Hy suggested the presence of a seventh antigen and prompted this study. STUDY DESIGN AND METHODS: Standard hemagglutination and polymerase chain reaction-based methods were used throughout. RESULTS: The patient's RBCs typed as Do(a-b+(w) ), Gy(a+(w) ), Hy+(w) , Jo(a+(w) ), and DOYA+(w) . Her serum agglutinated RBCs with common Dombrock phenotypes. Hy- RBC samples were very weakly reactive or nonreactive, Jo(a-) and DOYA- RBC samples were reactive, and Gy(a-) RBC samples were nonreactive. Reactivity was obtained with RBCs treated with papain or α-chymotrypsin, but not with RBCs treated with trypsin or dithiothreitol. DNA analysis showed the patient to be DO*793G (DO*B/DO*B), DO*323G, DO*350C, DO*547T, and DO*898G and revealed two homozygous nucleotide changes of DO*431C>A and DO*432C>A in Exon 2, which predicts a change of Ala (GCC) at Amino Acid 144 to Glu (GAA). This indicates that she is homozygous DO*B-WL with Nucleotide 431 and 432 changes, which without knowing the effect of the two novel changes, is predicted to encode the Do(a-b+), Gy(a+), Hy+, Jo(a+), DOYA+ phenotype. CONCLUSIONS: The antibody in the patient's plasma recognizes the high-prevalence antigen absent from her RBCs. The Ala144Glu change caused an absence of a high-prevalence Do antigen that we have named DOMR [provisional ISBT number 014007 (DO7)]. The absence of DOMR is associated with weakening of Do(b) , Gy(a) , Hy, Jo(a) , and DOYA antigens.