High-level mosaicism for 45,X in 45,X/46,X,+mar at amniocentesis in a pregnancy associated with positive non-invasive prenatal testing for Turner syndrome, normal male external genitalia and positive SRY in the fetus, a favorable fetal outcome, postnatal decrease of the 45,X cell line and cytogenetic discrepancy in various tissues.

Abstract

We present high-level mosaicism for 45,X in 45,X/46,X,+mar at amniocentesis in a pregnancy associated with positive non-invasive prenatal testing (NIPT) for Turner syndrome, normal male external genitalia and positive SRY in the fetus, a favorable fetal outcome, postnatal decrease of the 45,X cell line and cytogenetic discrepancy in various tissues. A 35-year-old, gravida 2, para 1, woman underwent amniocentesis at 16 weeks of gestation because of positive NIPT for Turner syndrome (Z score=-11.72 for X chromosome) at 10 weeks of gestation. Amniocentesis revealed a karyotype of 45,X[13]/46,X,+mar[8]. Simultaneous molecular analysis on the DNA extracted from uncultured amniocytes revealed the results of arr (X)×1, (Yp)×0-1 (0.63), (Yq)×0, (1-22)×2 in array comparative genomic hybridization (aCGH) and rsa(X)×1, Yp11.31×0-1, Yq11.21×0, (13, 18, 21)×2 in multiplex ligation-dependent probe amplification (MLPA). The parental karyotypes were normal. Prenatal ultrasound revealed normal male external genitalia. She was referred for genetic counseling, and continuing pregnancy was advised. A 2875-g male baby was delivered at 38 weeks of gestation with normal male external genitalia. The karyotypes of cord blood, umbilical cord and placenta were 46,X,+mar[27]/45,X[13], 46,X,+mar[24]/45,X[16] and 45,X[22]/46,X,+mar[18], respectively. SRY testing on cord blood revealed a positive result. When follow-up at age two months, the neonate was normal in development. The karyotype of peripheral blood was 46,X,+mar[25]/45,X[13]/46,X,idic r(Y) [2]. Interphase fluorescence in situ hybridization (FISH) analysis on 103 buccal mucosal cells using Yp11.2-specific probe RP11-119E4 and Xp22.31-specific probe RP11-143E20 showed that 90cells (90/103=87%) had double Yp signals, 3cells (3/103=3%) had single Yp signal and 10cells (10/103=10%) had no Yp signal. High-level mosaicism for 45,X in 45,X/46,X,+mar at amniocentesis with positive Yp and SRY can be associated with a favorable fetal outcome, postnatal decrease of the 45,X cell line and cytogenetic discrepancy in various tissues.