Familial transmission of a small supernumerary marker chromosome 8 identified by FISH: an update.

A father and his 2 daughters were previously determined to carry a small, supernumerary marker chromosome [Chudley et al., 1983]. The origin of this marker could not be determined by standard cytogenetic techniques. In this study, fluorescence in situ hybridization (FISH) studies identified the marker chromosome as a pericentric derivative of chromosome 8. The father has low grade mosaicism for this marker and is phenotypically normal. Both daughters are non-mosaic and show developmental delays and somewhat differing clinical findings. The phenotypes of the 2 sisters are compared with those previously reported for supernumerary der(8) patients. This is the first report of familial transmission of a supernumerary der(8) marker chromosome.