A case of apparent trisomy 21 without the Down's syndrome phenotype.
Open Access
- 1 July 1997
- journal article
- case report
- Published by BMJ in Journal of Medical Genetics
- Vol. 34 (7) , 597-600
- https://doi.org/10.1136/jmg.34.7.597
Abstract
We describe a case of apparent trisomy 21 that does not fulfill the criteria for the clinical diagnosis of Down's syndrome (DS). Our patient was subjected to karyotype analysis and found to have full, non-mosaic trisomy 21 in both blood lymphocytes and skin fibroblasts, while examination of the term placenta, which was performed earlier in the course of a different study, had shown mosaicism (73%) for trisomy 21. FISH analysis showed no obvious rearrangement of the DS chromosomal region in any of the chromosomes 21. Molecular analysis using polymorphic markers on chromosome 21 verified the existence of trisomy for the entire long arm of the chromosome and showed that the origin of the extra chromosome was maternal and was probably the result of a mitotic error. In contrast with the above, the clinical evaluation using the Jackson checklist of 25 signs failed to establish the diagnosis of DS. We believe that our patient might present mosaicism in other tissues that are not available for analysis and can be regarded as an extreme example in the continuous spectrum of karyotype phenotype associations in mosaic cases.Keywords
This publication has 21 references indexed in Scilit:
- An Integrated Map with Cosmid/PAC Contigs of a 4-Mb Down Syndrome Critical RegionGenomics, 1996
- Identification, Characterization, and Physical Mapping of 14 Polymorphic Simple Sequence Repeat Markers on Human Chromosome 21Genomics, 1994
- Isolation and Characterization of 14 CA-Repeat Microsatellites from Human Chromosome 21Genomics, 1993
- A prospective cytogenetic study of third‐trimester placentae in small‐for‐date but otherwise normal newbornsPrenatal Diagnosis, 1993
- Mitotic errors in somatic cells cause trisomy 21 in about 4.5% of cases and are not associated with advanced maternal ageNature Genetics, 1993
- Nuclear and chromosomal replication patterns in chorionic villi cells by bromodeoxyuridine labelling and DNA flow cytometryCell Proliferation, 1992
- A one-step efficient and specific non-radioactive non-fluorescent method for in situ hybridization of banded chromosomesChromosoma, 1990
- Linkage analysis of the human HMG14 gene on chromosome 21 using a GT dinucleotide repeat as polymorphic markerGenomics, 1990
- An embryogenic model to explain cytogenetic inconsistencies observed in chorionic villus versus fetal tissuePrenatal Diagnosis, 1988
- Clinical diagnosis of Down's syndromeClinical Genetics, 1976