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Chromosomal mosaicism in amniotic fluid cell cultures
Abstract:
Over the past 6 years, using in situ processing methods, we have identified 32 cases of mosaicism in amniotic fluid cell cultures prepared from 1,100 samples. Two of these (45,X/46,XX and 46,XX/47,XX, + 21) were called true mosaics because multiple colonies demonstrated the same abnormal chromosome complement, and on subsequent evaluation of the newborn blood or fetal tissues, mosaicism was confirmed. Of the remaining cases, 29 were designated as pseudomosaics because only single or partial colonies exhibited an aberrant chromosome complement, 12 having a trisomy 2 line. In the final case, a double trisomy was demonstrated in only one of eight colonies in the first culture, but in the culture from a repeat sample an additional two colonies showed the same double trisomy. Since no abnormal cells were observed in infant blood, it was postulated that the mosaicism may only have been present in the extraembryonic tissues. It is our conviction that the use of these cloning methods should diminish the danger of misdiagnosis in genetic amniocentesis.
Insights
This study identified 32 cases of chromosomal mosaicism in amniotic fluid cell cultures. Advanced cloning methods help distinguish true mosaicism from pseudomosaicism, reducing misdiagnosis risks in genetic amniocentesis.
Area of Science:
- Cytogenetics
- Prenatal Diagnosis
- Reproductive Medicine
Background:
- Chromosomal abnormalities detected during prenatal diagnosis can lead to complex clinical decisions.
- Distinguishing true fetal mosaicism from laboratory artifacts (pseudomosaicism) in amniotic fluid cultures is critical.
- In situ processing and colony-based analysis offer potential for improved diagnostic accuracy.
Purpose of the Study:
- To evaluate the incidence of chromosomal mosaicism in amniotic fluid cell cultures.
- To differentiate true mosaicism from pseudomosaicism using advanced culture techniques.
- To assess the clinical implications of mosaicism findings in prenatal genetic testing.
Main Methods:
- Analysis of 1,100 amniotic fluid samples over six years.
- In situ processing and colony selection for cytogenetic analysis.
- Confirmation of mosaicism in newborns or fetal tissues for true positive cases.
Main Results:
- Identified 32 cases of mosaicism out of 1,100 amniotic fluid samples.
- Confirmed two cases as true mosaicism (45,X/46,XX and 46,XX/47,XX,+21).
- Classified 29 cases as pseudomosaicism, with 12 showing a trisomy 2 line.
Conclusions:
- In situ processing and colony analysis are valuable for accurate mosaicism detection.
- The distinction between true mosaicism and pseudomosaicism is crucial for genetic counseling.
- These methods aim to minimize misdiagnosis risks associated with genetic amniocentesis.