SIGNIFICANCE OF MOSAIC ISOCHROMOSOME-20Q ON AMNIOCENTESIS

We report on 2 fetuses with prenatally diagnosed mosaic isochromosome 20q in amniotic fluid. Neither had an identifiable cytogenetic abnorma lity after birth. One infant developed a benign intracranial dermoid c yst at age 8 months. The other was completely normal in all respects. We are aware of 13 fetuses with this prenatally diagnosed chromosome f inding; all fetuses tested have had normal chromosomes on subsequent c ytogenetic studies and all, except one, have been morphologically norm al. Fetuses with mosaic isochromosome 20q identified on amniocentesis are most likely to be phenotypically and cytogenetically normal after birth. (C) 1993 Wiley-Liss, Inc.