Prenatal diagnosis of trisomy 4 mosaicism

Trisomy 4 mosaicism is rare. To our knowledge only two cases of prenatally diagnosed trisomy 4 mosaicism have been reported. One case resulted in a no rmal liveborn male, the other resulted in an abnormal liveborn female. The karyotype of our case at the time of amniocentesis was 47,XY,+4[3]/46,XY[33 ] and resulted in a normal liveborn male, FISH analysis using an alpha sate llite chromosome 4 probe was performed to confirm the cytogenetic findings. Follow-up chromosome analysis of cord blood, peripheral blood, foreskin, a nd umbilical cord fibroblasts showed a normal 46,XY male karyotype in all c ells. FISH analysis of cord blood, umbilical cord fibroblasts, and amniotic fluid cells demonstrated two signals in 246 nuclei (i.e., 46,XY) and three signals in six nuclei (i.e., 47,XY,+4), Here we describe the present case of trisomy 4 mosaicism, the literature is reviewed, and the significance of this finding is discussed. (C) 2000 Wiley-Liss, Inc.