Prenatal diagnosis of mosaic trisomy 12 associated with congenital overgrowth

摘要

A 36-year-old, gravida 3, para 2 woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Her prior two pregnancies resulted in uneventful vaginal deliveries at term. The mother did not have diabetes mellitus during this pregnancy. Cytogenetic analysis of cultured amniocytes revealed mosaic trisomy 12 with trisomy 12 cells in 42.9% (12/28) colonies. Among 28 colonies of cultured amniocytes, eight colonies had a karyotype of 47,XX,+12, four had a karyotype of 47,XX,+12/46,XX, and 16 had a karyotype of 46,XX. In the same in situ cultured slides, a calculation of 97 cultured amniocytes showed 23 cells with 47,XX,+12 and 74 cells with 46,XX. The parental karyotypes were normal. Prenatal ultrasound findings were unremarkable. She was referred to another hospital and underwent repeated amniocentesis and cordocentesis at 20 weeks of gestation. Interphase fluorescence in situ hybridization (FISH) analysis using a 12q11–q12-specific bacterial artificial chromosome (BAC) probe of RP11-496H24 showed three signals in 24.6% (16/65) and two signals in the remaining 75.4% (49/65) of uncultured amniocytes, indicating 24.6% mosaicism for trisomy 12 in the uncultured amniocytes at repeated amniocentesis (Fig. 1). Cytogenetic analysis of cultured amniocytes revealed a karyotype of 47,XX,+12[8]/46,XX[12] (Fig. 2). Among 20 colonies of cultured amniocytes investigated by in situ cultured method, eight colonies had a karyotype of 47,XX,+12, whereas the other 12 colonies had a karyotype of 46,XX, indicating 40% mosaicism for trisomy 12 in cultured amniocytes. Cytogenetic analysis of cord blood revealed a karyotype of 46,XX in 50/50 cultured lymphocytes. Level II ultrasound revealed fetal overgrowth, but no structural abnormalities. The woman elected to continue the pregnancy. At 36 weeks of gestation, a female baby with a birth weight of 4150 g (97th centile) and a length of 54 cm (>97th centile) was delivered. Interphase FISH analysis on 96 uncultured urinary cells using the bacterial artificial chromosome (BAC) probe of RP11-496H24 showed three signals in 24 uncultured urinary cells, indicating 25% (24/96) mosaicism for trisomy 12 in urinary epithelial cells (Fig. 3). The baby had normal psychomotor development and manifested no phenotypic abnormality at 2 months of age. Her body weight was 6800 g (97th centile) and body length was 59.1 cm (85th centile).