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Transfusion. 2011 Sep;51(9):1980-4. doi: 10.1111/j.1537-2995.2011.03110.x. Epub 2011 Mar 24.

New K103 β3 allele identified in a context of severe neonatal thrombocytopenia.

Author information

1
Platelet Immunology Laboratory, INTS, Paris, France.

Abstract

BACKGROUND:

A new β3 allele was identified in a severe case of neonatal alloimmune thrombocytopenia (<7 × 10(9) /L).

STUDY DESIGN AND METHODS:

Diagnosis was done by use of monoclonal antibody-specific immobilization of platelet (PLT) antigen for serologic analyses and polymerase chain reaction (PCR)-sequence-specific primers (SSP) and PCR-restriction fragment length polymorphism (RFLP) for genotyping. Direct sequencing of PCR product was done and mutant αIIbβ3 expressed in HEK-293 cells.

RESULTS:

Serologic analysis revealed in the maternal serum an anti-human PLT alloantigen (HPA)-1a alloantibody associated to an anti-α2β1. Anti-HPA-1a alloimmunization diagnosis was confirmed by genotyping showing maternofetal incompatibility. However, investigation of rare HPA polymorphisms revealed discrepant HPA-16b assignation between PCR-RFLP and PCR-SSP. Sequencing revealed a new c.385C>A mutation in the β3 coding sequence resulting in a false assignation of the HPA-16b allele by PCR-RFLP. This mutation leads to a Q103K substitution in mature β3. The K103-β3 form of the complex was expressed in HEK-293 cells but did not react with the maternal serum.

CONCLUSION:

We have characterized a new rare allele (frequency < 1%) of β3 that yields false HPA-16b genotyping in PCR-RFLP. This new case of false typing assignation emphasizes the necessity to use two genotyping techniques in diagnosis. This particularly applies for rare HPA polymorphisms when PLT phenotyping cannot be used.

[Indexed for MEDLINE]

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