RESUMO
The D antigen is one of the most immunogenic and clinically significant antigens of the Rh blood group system due to its various genotypes that encode for more than 450 different variants. Accurate RhD typing and D variant identification is crucial specially in prenatal screening during pregnancy. Women with RhD -ve phenotype are eligible to Rh immune globulin (RhIG) prophylaxis for the prevention of anti-D alloimmunization and hemolytic disease of the fetus and newborn (HDFN). However, there are some women who possess RhD variant alleles, who are mistakenly grouped as RhD positive and considered not eligible for RhIG prophylaxis, putting them at risk of anti-D alloimmunization and consequently leading to HDFN during subsequent pregnancies. Here, we describe two cases of RhD variants DAU2/DAU6 and Weak D type 4.1 in obstetric patients who were grouped as RhD +ve with negative antibody screening during routine serologic testing. Weak/Partial D molecular analysis using genomic DNA Red Cell Genotyping (RCG) revealed that both patients had RhD variants, one of which DAU2/DAU6 allele associated with anti-D alloimmunization. According to routine testing neither patients received RhIG or transfusion. In this case report we document to our knowledge the first reported cases of RhD variants among pregnant women in Saudi Arabia.
Assuntos
Gravidez , Sistema do Grupo Sanguíneo Rh-Hr , Feminino , Humanos , Gravidez/genética , Gravidez/imunologia , Alelos , Eritroblastose Fetal/imunologia , Eritroblastose Fetal/prevenção & controle , Eritroblastose Fetal/terapia , Genótipo , Fenótipo , Sistema do Grupo Sanguíneo Rh-Hr/genética , Sistema do Grupo Sanguíneo Rh-Hr/imunologia , Imunoglobulina rho(D)/uso terapêutico , Arábia SauditaAssuntos
Árabes/genética , Sistema do Grupo Sanguíneo de Kell/genética , Glicoproteínas de Membrana/genética , Metaloendopeptidases/genética , Adulto , Alelos , Especificidade de Anticorpos , Tipagem e Reações Cruzadas Sanguíneas , DNA/genética , Éxons/genética , Feminino , Humanos , Isoanticorpos/sangue , Isoanticorpos/imunologia , Glicoproteínas de Membrana/imunologia , Metaloendopeptidases/imunologia , Fenótipo , Gravidez , Arábia Saudita , Alinhamento de Sequência , Deleção de Sequência , Homologia de Sequência do Ácido NucleicoRESUMO
BACKGROUND: The Scianna (SC) blood group system comprises seven antigens. They reside on the erythroblast membrane-associated glycoprotein (ERMAP). The ERMAP and RHCE genes are juxtaposed to each other on chromosome 1. We report a novel SC antigen. STUDY DESIGN AND METHODS: Blood samples came from a patient and his two sisters in Saudi Arabia. To investigate the antibody specificity we used the column agglutination technique and soluble recombinant ERMAP protein. The significance of anti-SCAR was evaluated by the transfusion history and a monocyte monolayer assay. We determined the genomic sequence of ERMAP and RHCE genes. RESULTS: The patient's serum showed an antibody of titer 8 against a high-prevalence antigen. The soluble recombinant ERMAP protein inhibited the antibody. The propositus genotyped homozygous for an ERMAP:c.424C>G variant, for which his sisters were heterozygous. The c.424C>G variant occurred in the SC*01 allele in one haplotype with the RHCE*03 (RHCE*cE) allele. No signs of hemolysis occurred following an incompatible blood transfusion. The monocyte monolayer assay was negative. CONCLUSIONS: We characterized a high-prevalence antigen, with the proposed name "SCAR," which is the eighth antigen of the Scianna blood group system (proposed designation 013.008). Individuals homozygous for ERMAP:p.(Gln142Glu) protein variant can produce anti-SCAR. Although we did not observe any sign of hemolysis at this time, the anti-SCAR prompted a change of the treatment regimen. A review of the known reports indicated that all SC alloantibodies of sufficient titer should be considered capable of causing hemolysis.
