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Multiple recurrence of trisomy 21 Down syndrome
K G Nielsen1, H Poulsen, M Mikkelsen
1Department of Medical Genetics, J.F.Kennedy Institute, Glostrup/Copenhagen, Denmark.
Human Genetics
|January 1, 1988
Summary
This study reports an extraordinary family with multiple children diagnosed with Down syndrome (trisomy 21). Ovarian mosaicism in the mother offers a partial explanation for this high incidence of trisomy 21 in offspring.
Area of Science:
- Genetics
- Human Reproduction
- Cell Biology
Background:
- Recurrent trisomy 21 (Down syndrome) in offspring is rare.
- Understanding the genetic and cellular mechanisms behind recurrent aneuploidy is crucial for genetic counseling.
Observation:
- A family presented with four chromosomally confirmed cases of trisomy 21 and at least two additional clinical diagnoses of Down syndrome.
- No evidence of chromosomal mosaicism was detected in lymphocyte or skin fibroblast samples from either parent.
- Analysis of an ovarian biopsy from the mother revealed the presence of a trisomic cell line.
Findings:
- The identification of a trisomic cell line in the mother's ovarian tissue provides a potential, though incomplete, explanation for the high rate of Down syndrome in this family.
- Standard cytogenetic analyses of parental somatic cells did not reveal mosaicism, suggesting the aneuploidy originates from germline or early developmental events.
Implications:
- This case highlights the complexity of recurrent aneuploidy and suggests that ovarian mosaicism may contribute to an increased risk of Down syndrome.
- Further research is needed to fully elucidate the mechanisms leading to such extraordinary familial recurrence of trisomy 21.
- Findings have implications for prenatal diagnosis and genetic counseling for families with a history of multiple aneuploid conceptions.