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46,XY,18q+/46,XY,18q− mosaicism in a fragile X prenatal diagnosis
Author(s) -
RodriguezRevenga Laia,
Badenas Celia,
Madrigal Irene,
Sánchez Aurora,
Soler Anna,
Carrió Ana,
Milà Montserrat
Publication year - 2005
Publication title -
prenatal diagnosis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.956
H-Index - 97
eISSN - 1097-0223
pISSN - 0197-3851
DOI - 10.1002/pd.1150
Subject(s) - amniocentesis , chorionic villus sampling , prenatal diagnosis , biology , karyotype , chorionic villi , dup , trisomy , genetics , fragile x syndrome , chromosome abnormality , fetus , chromosome , microbiology and biotechnology , gene duplication , gene , pregnancy
Abstract Objectives We describe a fetus with confined placental mosaicism for 46,XY,dup(18)(q21q23)/46,XY, del(18)(q21) in which finally the 18q‐ cell line formed the embryo. This prenatal diagnosis was performed on a pregnant woman carrying a premutation in the FMR1 gene. The purpose of the current study was to characterise the final fetus genotype and to discuss how this chromosomal abnormality was originated. Methods Conventional cytogenetic analyses were performed from chorionic villi, amniocytes, and fetal blood samples in order to establish the fetal chromosome constitution. Molecular studies with microsatellite markers and CGH were carried out to this end. PCR and Southern blot were used to analyse the CGG‐repeat region of the FMR1 gene. Results An initial chorionic villi sample analysis showed a normal allele for the fragile X syndrome, but an abnormal 46,XY,dup(18)(q21q23) karyotype. Amniocentesis was subsequently performed, and a different 46,XY,del(18)(q21) cell line was detected. Re‐examination of original chorionic villi sample evidenced a mosaicism for 46,XY,dup(18)(q21q23)/46,XY,del(18)(q21). Molecular findings allowed us to determine that the deletion expands at least 20 Mb and that it is paternally inherited. Conclusion Two different cell lines with structural abnormalities on chromosome 18 were formed as a consequence of an unequal sister chromatid exchange during the first post‐zygotic division. This case reinforces the necessity of performing a karyotype in all prenatal diagnosis even when the indication is for a monogenic disease. Copyright © 2005 John Wiley & Sons, Ltd.