New mutation in the platelet beta3-integrin gene: implication for the diagnosis of fetomaternal alloimmunization.
BACKGROUND
Fetal ventriculomegaly is a relatively common finding and fetomaternal alloimmune thrombocytopenia may be one of the causes.


METHODS
Such a case discovered at 21 weeks of gestation leading to platelet (PLT) immunologic testing is reported here. PLT genotyping was performed by polymerase chain reaction (PCR)-sequence-specific primers (SSPs) method and PCR-restriction fragment length polymorphism (RFLP) analysis. Serologic investigation was done with the monoclonal antibody-specific immobilization of PLT antigens technique.


RESULTS
The mother was found to be HPA-1b homozygous and the father HPA-1a homozygous with PCR-SSP, but the mother was found to be HPA-1 heterozygous by phenotyping. This result was confirmed by PCR-RFLP. Sequencing of the glycoprotein IIIa exon 3 revealed a heterozygous mutation 262T > C, which does not induce an amino acid change. It is localized in the sequence of the antisense primer of the HPA-1 PCR-SSP, inducing the sole amplification of the DNA copy bearing the HPA-1b allele.


CONCLUSIONS
Even if such mutations are a rare event, PLT phenotyping is still of interest to avoid rare false PLT typing assignation, the unknown polymorphism being only discovered by such a combination of techniques.
Bertrand
Gerald
G
Platelet Immunology Unit, INTS, Paris, France.
Bianchi
Frederic
F
Chenet
Christophe
C
Martageix
Corinne
C
Blanchet
Patricia
P
Bäumler
Marcel
M
Kaplan
Cecile
C
D016824:Antigens, Human Platelet / Q000276:immunology*; D001483:Base Sequence; D001792:Blood Platelets / Q000276:immunology; D005091:Exons; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis* / Q000276:immunology; D006801:Humans; D039661:Integrin beta3 / Q000235:genetics*; D007518:Isoantibodies / Q000276:immunology; D008431:Maternal-Fetal Exchange / Q000276:immunology*; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D013921:Thrombocytopenia / Q000175:diagnosis* / Q000276:immunology
D016824:Antigens, Human Platelet; D039661:Integrin beta3; D007518:Isoantibodies; C083451:human platelet antigen 1b