A novel double-variant RHAG allele leads to Rh_mod phenotype.

AIMS/OBJECTIVES:We aimed to analyse the molecular backgrounds and red blood cell (RBC) antigen expression of a male blood donor with Rh_mod phenotype and his family members. BACKGROUND:Rh deficiency phenotypes are rarely found worldwide and are characterised by the lack of Rh antigen expression on RBCs. During routine screening, we found a blood donor who seemingly lacked Rh antigens. Therefore, we recruited the donor and his family for further investigation. METHODS:RBC serotyping and antibody screening/identification were performed for each sample. A routine blood examination was also conducted. RHD, RHCE and RHAG were sequenced at the genomic DNA or RNA level. Eleven antigens or proteins associated with Rh complex were tested using flow cytometry analysis. RESULTS:The proband and one of his brothers showed extremely weak D antigen and Rh expression levels but did not manifest anaemia. Most of the expressed RBC antigens of the two Rh-deficient individuals were similar to the previously reported cases but with some exceptions. Molecular analyses demonstrated homozygous expression of a novel RHAG allele, namely, c.[572G>A;707A>C], both in the proband and one of his brothers. CONCLUSIONS:To our knowledge, we identified the second double-variant RHAG allele and the first one related to Rh_mod phenotype. The novel allele was also confirmed to be heritable by family analyses.

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