Identification and pedigree analysis of a hidden partial D antigen with rare RHD*DV.1 allele.

INTRODUCTION

An 85-year-old O D-positive male with a history of multiple D-positive RBC transfusions (10.5 units in 2020, 5.5 units in 2023) presented with severe anemia in June 2024. Unexpected antibodies were found in his plasma, and crossmatching was incompatible with all O D-positive donor RBCs. In this article, we document the methodology for confirming a hidden partial D antigen with rare RHD*DV.1 allele variant, with the objectives of elucidating the characteristics of this rare allele and establishing evidence-based transfusion guidelines.

METHODS

This partial D antigen was identified using column agglutination and tube methods for the patient in this case. Subsequent adsorption-elution assays characterized the antibody mixture in the his plasma. RHD gene sequencing confirmed the specific mutations and zygosity.

RESULTS

Compared with the 4+ agglutination observed in column agglutination testing for the patient in this instance, a much weaker reaction (2+ agglutination) was noted in tube testing. RHD gene sequencing revealed 2 variations in exon 5-c.667T>G and c.697G>C-consistent with the RHD*DV.1 allele. Both of the patient's sons were genotyped as RHD*DV.1/RHD*01, confirming the inheritance of this allele from their father. Analysis of the patient's haplotypes showed only 1 single-nucleotide variation (formerly single-nucleotide polymorphism) difference (c.801 + 108G>A) located in intron 5. This finding demonstrates that the 2 exon 5 variations reside on separate haplotypes, confirming that this patient was a definitive homozygote for RHD*DV.1.

DISCUSSION: For women of childbearing potential, pretransfusion screening using the tube method remains a vital component in the early detection of D antigen variants and is essential for preventing alloimmunization.