mosaicism

Full Definition

Mosaicism occurs when an individual has two or more genetically different cell lines derived from a single fertilized embryo. In prenatal diagnosis, mosaicism can affect interpretation of genetic testing results, as the proportion of abnormal cells may vary between tissues. Confined placental mosaicism (CPM) occurs when chromosomal abnormalities are present only in placental tissue, potentially leading to false-positive results in chorionic villus sampling. True fetal mosaicism may result in milder phenotypes than complete chromosomal abnormalities.

Usage

Usage note: Distinguish from confined placental mosaicism (CPM) which affects only placental tissue.

In Context

• "Mosaicism was suspected when CVS results differed from subsequent amniocentesis findings." — Genetic counseling report
• "The presence of mosaicism complicated risk assessment and required additional testing." — Prenatal diagnosis summary