AN ACCESSORY MARKER DERIVED FROM CHROMOSOME-20 AND ITS COEXISTENCE WITH A MOSAIC TRISOMY-20 CELL-LINE

We report a 16-month-old boy with delayed psychomotor development, dys morphic features, and failure to thrive. He had a mosaic karyotype det ected prenatally: mos 46,XY/47,XY, +r(20)/47,XY, +20. After birth, the abnormal cell lines were confirmed in a number of tissues. The small ring chromosome was identified using fluorescence in situ hybridizatio n as derived from chromosome 20. We compared our patient with previous ly reported cases of mosaic trisomy 20 detected prenatally and associa ted with an abnormal phenotype. In an attempt to characterize an r(20) syndrome, we also compared our case with two similar reports in the l iterature.