Mosaic distal 10q deletion or 46,XY,del(10) (q26.13)/46,XY at amniocentesis and cordocentesis in a pregnancy associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome

We present mosaic distal 10q deletion at prenatal diagnosis in a pregnancy associated with a favorable fetal outcome. A 40-year-old, gravida 2, para 0, woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY, del(10) (q26.13)6/46,XY17. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes showed 35% mosaicism for the 10q26.13q26.3 deletion. At 22 weeks of gestation, she underwent cordocentesis which revealed a karyotype of 46,XY,del(10) (q26.13)16/46,XY24. Prenatal ultrasound findings were normal. At 24 weeks of gestation, she was referred for genetic counseling, and repeat amniocentesis revealed a karyotype of 46,XY,del(10) (q26.13)4/46,XY22. The parental karyotypes were normal. Molecular genetic analysis on uncultured amniocytes revealed no uniparental disomy (UPD) 10 by quantitative fluorescence polymerase chain reaction (QF-PCR), arr 10q26.13q26.3 × 1.6 (40% mosaicism) by aCGH, and 29.8% (31/104 cells) mosaicism for the distal 10q deletion by interphase fluorescence in situ hybridization (FISH). The woman was advised to continue the pregnancy, and a phenotypically normal 2,900-g male baby was delivered at 39 weeks of gestation. The cord blood had a karyotype of 46,XY,del(10) (q26.13)6/46,XY34, and both the umbilical cord and the placenta had the karyotype of 46,XY. When follow-up at age four months, the neonate was normal in phenotype and development. The peripheral blood had a karyotype of 46,XY,del(10) (q26.13)5/46,XY35, and interphase FISH analysis on buccal mucosal cells showed 8% (8/102 cells) mosaicism for distal 10q deletion. Mosaic distal 10q deletion with a normal cell line at prenatal diagnosis can be associated with a favorable fetal outcome and perinatal progressive decrease of the aneuploid cell line.