Cell death as a possible mechanism for tissue limited mosaicism in Pallister-Killian syndrome.

Pallister-Killian syndrome is a chromosomal mosaic syndrome with a normal and an isochromosome 12p cell line, the latter rarely seen in peripheral blood. The isochromosome 12p cell line decreases with serial passages of fibroblasts in vitro and with age of patient in vivo. To evaluate cell death as a possible mechanism for loss of the abnormal cell line, amniocytes from a fetus with Pallister-Killian syndrome were identified as normal or aneuploid using a chromosome 12 alpha-satellite DNA probe by fluorescent in situ hybridization (FISH) and then subsequently stained with Annexin V, which stains the cytoplasm of cells that are dying. Although not conclusive, our preliminary results suggest that the abnormal cell line is going through apoptosis or necrosis at a higher rate than normal cells. Cell death may be a possible mechanism for decrease of the aneuploid cell line in patients with Pallister-Killian syndrome.