Introduction

Accurate identification of the RhD antigen is essential for safe blood transfusion and the management of Rh-incompatible pregnancies. Clinicians increasingly rely on molecular methods to resolve discrepancies between serological tests and genetic profiles. However, a recent study has identified a novel structural variant in the southern Chinese Han population that significantly compromises RHD genotyping accuracy. This discovery emphasizes the need for continuous refinement of genetic testing protocols.

Discovery of the RHD-CE-TMEM50A-D Variant

Researchers recently uncovered a complex structural variation of the RHD gene using advanced long-read sequencing technology. This novel allele, named RHD-CE-TMEM50A-D, features a 688 bp deletion and a substantial 21.8 kb insertion within the non-coding region of RHD exon 10. Specifically, the insertion involves genetic material from the RHCE gene and the TMEM50A gene. Furthermore, the variant appears relatively frequently, occurring in approximately 1 in 49 chromosomes within the southern Chinese Han population.

Challenges to RHD Genotyping Accuracy

Many routine molecular assays target the non-coding regions of RHD exon 10 to design specific primers. Consequently, the structural changes in this novel allele often lead to "allele dropout," where the genetic test fails to detect the presence of the RHD gene. Although the D antigen expression itself remains largely unchanged, the resulting inconclusive data can mislead clinicians. Therefore, improving RHD genotyping accuracy requires the inclusion of new primer sets that can recognize these East Asian-specific variations.

Clinical Implications for Transfusion Medicine

The prevalence of this variant in East Asian heritage individuals suggests that current genotyping kits may yield inaccurate results in this demographic. Since the variant does not significantly alter the D antigen phenotype, the primary risk lies in the genotype-phenotype discrepancy. Moreover, such errors could affect the management of RhD-negative pregnancies and the selection of blood for transfusion. Hematologists and laboratory specialists must remain vigilant regarding regional genetic diversity to ensure patient safety.

Frequently Asked Questions

What is the RHD-CE-TMEM50A-D variant?

It is a novel structural variant of the RHD gene involving a large insertion and a small deletion in exon 10. It is primarily found in the southern Chinese Han population.

How does this variant affect clinical testing?

The variant causes allele dropout in standard RHD genotyping assays, potentially leading to inconclusive or false-negative results despite normal D antigen expression on red cells.

Why is RHD genotyping accuracy important for pregnant women?

Accurate genotyping ensures that RhD-negative pregnant women receive appropriate Rh immunoglobulin prophylaxis and helps in the management of hemolytic disease of the fetus and newborn (HDFN).

Disclaimer: This content is for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

Wen J et al. An RHD gene variant, common in southern Chinese Han, involves a short 688 bp deletion and a long 21.8 kb insertion in the RHD exon 10 non-coding region, affecting the accuracy of red cell genotyping. J Transl Med. 2026 May 12. doi: 10.1186/s12967-026-08183-1. PMID: 42120998.

Flegel WA. Molecular genetics and clinical applications of Rh. Transfus Apher Sci. 2011;44(1):81-91. doi: 10.1016/j.transci.2010.12.011.

Denomme GA. Molecular basis of the Rhesus system. ISRN Hematol. 2011;2011:190217. doi: 10.5402/2011/190217.