Prenatal diagnosis of mosaicism for trisomy 11 in a single colony at amniocentesis in a pregnancy with a favorable outcome.

OBJECTIVE: We present prenatal diagnosis of mosaicism for trisomy 11 in a single colony at amniocentesis with a favorable outcome. CASE REPORT: A 34-year-old woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a result of 47,XY,+11[1]/46,XY[9]. In 10 colonies of cultured amniocytes, all five cells in one colony had a karyotype of trisomy 11, while the rest nine colonies had a normal karyotype. The parental karyotypes were normal. Repeat amniocentesis was performed at 19 weeks of gestation. Interphase fluorescence in situ hybridization (FISH) was applied on the uncultured amniocytes, and the result showed no trisomy 11 signals in 56/56 uncultured amniocytes. Uniparental disomy (UPD) 11 was excluded by polymorphic DNA marker analysis. The cultured amniocytes at repeat amniocentesis had a karyotype of 46,XY. Prenatal ultrasound findings were unremarkable. A healthy 3084-g male baby was delivered at 38 weeks of gestation. The karyotype of cord blood lymphocytes was 46,XY. The boy was phenotypically normal at age 10 months at follow-ups. The interphase FISH analysis on urinary cells revealed no trisomy 11 signal.
CONCLUSION: Mosaicism for trisomy 11 in a single colony at amniocentesis without UPD 11 can be associated with a favorable outcome.