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Down-Turner syndrome: case report and review
G J Van Buggenhout1, B C Hamel, J C Trommelen
1Department of Human Genetics, University Hospital Nijmegen, The Netherlands.
Journal of Medical Genetics
|October 1, 1994
Summary
Down-Turner mosaicism, a rare genetic condition (45,X/46,X,+21/47,XY,+21), presents with features of both Down syndrome and Ullrich-Turner syndrome. This review analyzes 28 cases, highlighting varied clinical presentations and chromosomal configurations.
Area of Science:
- Genetics
- Developmental Biology
- Human Biology
Background:
- Down-Turner mosaicism is a rare chromosomal abnormality involving variations of the X chromosome and chromosome 21.
- Understanding the genetic basis and phenotypic spectrum of mosaic conditions is crucial for accurate diagnosis and management.
Observation:
- This study reviews 28 cases of Down-Turner mosaicism, including a male patient with a 45,X/46,X,+21/47,XY,+21 karyotype.
- Clinical features of Down syndrome were universally observed, while 61% exhibited a combination of Down syndrome and Ullrich-Turner syndrome features.
- Mosaicism involved multiple cell lines in most patients, with varying numbers of cell lines reported.
Findings:
- Phenotypic presentation ranged from female external genitalia (21 patients) to male (4 patients) and ambiguous genitalia (3 patients).
- Only 21% of the reviewed patients carried a Y chromosome, a lower incidence than anticipated.
- Overlapping clinical stigmata between Down syndrome and Ullrich-Turner syndrome can complicate diagnosis.
Implications:
- Accurate diagnosis of Down-Turner mosaicism requires careful evaluation of both chromosomal makeup and phenotypic presentation.
- Further research is needed to understand the variable expressivity and genotype-phenotype correlations in this rare condition.
- This review contributes to the understanding of rare chromosomal disorders and their impact on human development.