Alloanti‐D in a DBT pregnant woman responsible for hemolytic disease of the fetus and newborn: Molecular study and genetic counseling

Abstract

BACKGROUND: While some partial D patients are not detected in routine D typing due to strong positive reactions with the commercially available anti-D reagents used, clinically significant alloanti-D against the absent epitopes can be produced following immunization with D-positive (D+) erythrocytes. This study aimed to characterize the allelic variant underlying the D+ phenotype in an alloimmunized, pregnant woman (anti-D titer: 64) and to provide genetic counselling to her close family members.MATERIALS AND METHODS: The proband and five family members were investigated in the study. Standard hemagglutination techniques were used in phenotyping and titration studies. A quantitative multiplex PCR of short fluorescent fragment (QMPSF) strategy was performed for RH genotyping.RESULTS: Our investigation revealed that the proband genotype was RHD*14.02/RHD*01N.01 responsible for a partial D phenotype, i.e. DBT. QMPSF analysis showed that the father and one of her brothers were heterozygous for RHD*14.02/RHD*01. The newborn presented with signs and symptoms of hemolytic disease of the fetus and newborn (HDFN), requiring medical intervention.DISCUSSION: The RHD variant identified in the maternal sample was responsible for a partial D phenotype. This case highlights the limitations of routine serologic typing for the D antigen, which misidentified a partial D phenotype as D+, preventing the patient from receiving appropriate prophylactic RhIg treatment. Interestingly, the QMPSF-based strategy resulted in a simple, reliable and effective method for a relevant allele characterization in all family members. Noteworthy, genetic counselling was provided to the proband´s brother carrying the RHD*14.02 variant at the heterozygous state with a RHD*01 allele.