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Discordant prenatal diagnosis of trisomy 21 due to mosaic structural rearrangements of chromosome 21
Author(s) -
Brisset Sophie,
Aboura Azzedine,
Audibert François,
Costa JeanMarc,
L'Herminé Aurore Coulomb,
Gautier Valérie,
Frydman René,
Tachdjian Gérard
Publication year - 2003
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.620
Subject(s) - isochromosome , karyotype , amniocentesis , biology , trisomy , dicentric chromosome , genetics , aneuploidy , trophoblast , chromosome , chromosomal rearrangement , marker chromosome , prenatal diagnosis , microbiology and biotechnology , fetus , pregnancy , placenta , gene
Abstract Objectives Trisomy 21 mosaicism associated with a structural rearrangement of chromosome 21 is uncommon. We report on two prenatal diagnoses in which karyotypes showed mosaicism with an aberrant cell line, including a structural rearrangement of chromosome 21. Methods Both these cases were associated with increased nuchal translucency. Conventional and molecular cytogenetic analyses were performed on uncultured and cultured trophoblast and amniotic fluid cells. Results In Case 1, analysis of trophoblast cells revealed an abnormal karyotype of 47,XX,+mar.ish der(13/21)(D13Z1/D21Z1+)/46,XX. The amniocentesis showed a free non‐mosaic trisomy 21. In Case 2, the trophoblast direct analysis showed a normal male karyotype whereas the long‐term culture revealed a mosaicism for a dicentric long‐arm isochromosome 21: 46,XY,idic(21)(p11)/45,XY,−21/46,XY. Amniocentesis showed an unbalanced non‐mosaic karyotype 46,XY,idic(21)(p11) resulting therefore in trisomy for the long arm of chromosome 21. Conclusion Our cases underline the importance of combining the direct analysis and long‐term culture of trophoblast and emphasise the need for confirmatory studies in other tissues when mosaicism of structural rearrangement is encountered in chorionic villi. The meiotic and mitotic mechanisms of formation of these structural rearrangements of chromosome 21 are discussed. Copyright © 2003 John Wiley & Sons, Ltd.