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Background: In the RH blood group genes, molecular variants that alter antigen expression with potential clinical relevance are frequently identified and reported in the literature. Study Design and Methods: A pregnant woman in her first pregnancy, who originates from Japan, was typed by routine serological testing. The RHCE gene was investigated to identify single nucleotide variants (SNVs) and/or structural variants by a commercial platform, Sanger sequencing, and quantitative multiplex PCR of short fluorescent fragments. The haplotypes were determined by sequencing PCR fragments generated from genomic DNA and subcloned into a plasmid vector. Effect on splicing was predicted by bioinformatics tools, including SpliceAI and the splicing module of Alamut. In parallel, functional analysis was carried out by a minigene splicing assay. Results: A patient with no transfusion history was typed RH:1,2w,3,4,5w. An unreported single variant was identified in RHCE intron 4 at the heterozygous state: c.634+4A>G. Minigene splicing assay showed that this SNV decreases significantly the relative abundance of the full-length transcript, in accordance with the predictions made by the Alamut tools, but not SpliceAI, suggesting expression of a normal RhCE protein. Conclusion:Overall, the novel RHCE*02(c.634+4A>G) allele alters quantitatively, but not qualitatively, the expression of C and e in the RH blood group system, indicating that the patient is not at risk for alloimmunization and may safely receive C+e+ red blood cell units. This report illustrates the relevance of functional assays for the interpretation of rare variants and, specifically, how it may help guide transfusion management in patients.

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