Fatal haemolytic transfusion reaction due to anti‐En ^a and identification of a novel GYPA c. 295delG variant in a Thai family

Background and Objectives High-frequency antigen En(a) (MNS 28) is expressed on glycophorin A (GPA). En(a-) individuals can form anti-En(a) when exposed to GPA. A Thai patient formed an antibody that reacted against all reagent red blood cells (RBCs). The patient received incompatible blood resulting in a fatal haemolytic transfusion reaction (HTR). This study aimed to characterize the antibody detected in the patient and investigate the cause of HTR. Materials and Methods Blood samples from the patient and three of his family members were investigated. Massively parallel sequencing (MPS) and DNA-microarray were used for genotyping. Standard haemagglutination techniques were used for phenotyping and antibody investigations. Results DNA sequencing showed the patient was homozygous for GYPA*M c.295delG (p.Val99Ter) predicting En(a-). Three family members were heterozygous for GYPA c.295delG. MPS and DNA-microarray predicted the patient was N- discordant with the N+ RBC phenotype. The patient's plasma was positive with enzyme/chemical-treated reagent RBCs but failed to react with En(a-) and (MMk)-M-k RBCs. Conclusion The GYPA c.295delG variant prevented GPA expression on RBCs resulting in En(a-) phenotype. The N+ phenotype result was probably due to the anti-N typing reagent detecting 'N' (MNS30) on GPB. The patient's alloantibody has anti-En(a) specificity.