First identification and molecular characterisation of a rare D– – donor in Saudi Arabia

BACKGROUND AND OBJECTIVES: The D- - phenotype is an exceptionally rare Rh configuration characterised by the expression of the D antigen but absence of all RHCE-encoded antigens. A few molecularly defined cases have been documented globally. MATERIALS AND METHODS: Gel microcolumn techniques were employed in this work to conduct serologic testing. Genotyping using ID RHD XT and ID CORE XT assays was performed, after which next-generation sequencing was performed on the RH promoter, exons 1-10 and introns 2-3 to enable definitive alleles to be identified. RESULTS: Serologic phenotyping showed D+ C- c- E- e-. Molecular analysis identified homozygosity for the RHCE*CeN.08 allele (RHCE*02N.08) a hybrid in which RHCE exons 3-9 are replaced by the corresponding RHD sequence together with two conventional RHD*01 alleles, consistent with the D- - phenotype. CONCLUSION: This is the first molecularly confirmed D- - donor reported in Saudi Arabia and the wider Middle East, and the first description of the RHCE*CeN.08 allele in this region. The finding extends the geographic distribution of this rare hybrid and underscores the value of combined serologic and high-resolution molecular testing for identifying and supporting D- - donors and patients.