45,X/46,XX at the first amniocentesis, and 45,X/47,XXX/46,XX at the repeat amniocentesis and at birth in a pregnancy associated with a favorable fetal outcome, perinatal progressive decrease of the 45,X cell line and cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes

Abstract

Objective: We present 45,X/46,XX at the first amniocentesis, and 45,X/47,XXX/46,XX at the repeat amniocentesis and at birth in a pregnancy associated with a favorable fetal outcome, perinatal progressive decrease of the 45,X cell line and cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes.

Case report: A 43-year-old, gravida 3, para 1, woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 45,X[4]/46,XX[20]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed arr (X) × 3 [0.24], consistent with 24% mosaicism for triple X. Repeat amniocentesis at 20 weeks of gestation revealed the result of 45,X[17]/47,XXX[8]/46,XX[121]. She was referred for genetic counseling, and the third amniocentesis performed at 30 weeks of gestation revealed the result of 45,X[3]/47,XXX[2]/46,XX[16]. The mother had a karyotype of 46,XX. aCGH analysis on the DNA extracted from uncultured amniocytes showed arr Xp22.33q28 × 2.2 (log₂ ratio = 0.15), consistent with 20% mosaicism for triple X. Interphase fluorescence in situ hybridization (FISH) analysis on 100 uncultured amniocytes showed that 11 cells (11%) were monosomy X, seven cells (7%) were triple X, and the others were disomy X. At 39 weeks of gestation, a 3,620-g phenotypically normal female baby was delivered without any phenotypic abnormality. The karyotypes of cord blood, umbilical cord and placenta were 47,XXX[7]/45,X[1]/46,XX[32], 47,XXX[13]/46,XX[27] and 47,XXX[2]/46,XX[38], respectively. When follow-up at age one month, the neonate was phenotypically normal, and FISH analysis on 106 buccal mucosal cells showed that eight cells (7.5%) were monosomy X, seven cells (6.6%) were triple X, and the others were disomy X.

Conclusion: Mosaic 45,X/46,XX at amniocentesis may be in fact mosaic 45,X/47,XXX/46,XX and can be associated with a favorable fetal outcome and perinatal progressive decrease of the 45,X cell line.

Keywords: 45,X/46,XX; 45,X/47,XXX/46,XX; Amniocentesis.