Compound heterozygous RHCE null genotype underlying D-- phenotype in a Chinese pregnant woman: molecular characterization and sequential transfusion strategy

The D-- phenotype is an extremely rare Rh blood group variant with absence of C, c, E, and e antigens but preserved D expression, predisposing to anti-Rh17 alloimmunization and hemolytic disease of fetus and newborn (HDFN). We report a 25-year-old Chinese woman (gravida 3, para 1) with D+C-c-E-e- phenotype and a history of severe neonatal jaundice and fetal demise. In her current pregnancy, admitted at 25⁺⁵ weeks for elevated fetal middle cerebral artery peak systolic velocity. PacBio sequencing (proband and her parents) and Oxford Nanopore whole-genome sequencing (ONT WGS; proband) were performed. PacBio sequencing preliminarily identified a compound heterozygous state at the RHCE locus involving two distinct RHCE-null haplotypes, a paternal complex structural variant and a maternal RHCE*02N.03 null allele with seven mutations. Subsequent ONT WGS resolved a novel paternal chimeric RHD-TMEM50A-RHCE rearrangement arising from dual recombination events. Serological and family evidence suggest that the maternal RHCE*02N.03 allele with c.486 + 1G>A results in a C-e- null phenotype in the compound heterozygous state. Four serial intrauterine transfusions used allogeneic D-- donor blood or maternal autologous washed irradiated packed red blood cells. All transfusions were well tolerated, with delivery at 37 weeks by cesarean section and favorable neonatal outcomes. This case demonstrates a sequential transfusion strategy for D-- pregnancies-prioritizing allogeneic D-- blood from rare donor networks when available, with maternal autologous blood as a safe alternative-and, through complementary PacBio and ONT WGS, adds evidence that complex RHD-RHCE inversion-recombination events may represent recurret mechanisms in the Chinese population while refining RHCE*02N.03 annotation from C- to C-e-.