A prenatal case of partial trisomy 21 (q22.2q22.3), resulting from a paternal insertion translocation ins(16;21) and uncovered by QF-PCR, and characterized by array CGH and FISH

Detection of partial deletion and mosaicism using quantitative fluorescent polymerase chain reaction: Case reports and a review of the literature

Background

Aneuploidy of chromosomes 13, 18, 21, X, and Y can be detected by the quantitative fluorescence polymerase chain reaction (QF‐PCR) performed with short tandem repeat (STR) markers. Although QF‐PCR is designed to detect whole chromosome trisomy, the partial deletion or mosaic of chromosomes may also be detected.

Methods

Partial deletion or mosaic of chromosomes in three cases was detected by QF‐PCR. Karyotyping and chromosome microarray analysis(CMA) were performed. We further reviewed the clinical utility of QF‐PCR in detecting mosaicisms and deletions/duplications.

Results

QF‐PCR demonstrated structurally abnormal 21, X, and Y chromosomes in primary amniotic cells. QF‐PCR results in these three cases showed abnormal peak height/peak area, which could not be interpreted according to the kit instructions. QF‐PCR results suggested that there were partial deletions or mosaicism, which were confirmed by karyotyping and CMA.

Conclusion

In addition to detecting trisomies of whole chromosomes, QF‐PCR can also detect deletion and mosaicism of chromosomes 13, 18, 21, X, and Y, which could suggest the presence of copy number variants (CNVs). Additional testing with genetic technologies, such as karyotyping or microarrays, is recommended when an uninformative pattern is suspected.