Mosaic 45,X/46, XX at amniocentesis with high-level mosaicism for 45,X in a pregnancy with a favorable fetal outcome...

We present mosaic 45,X/46, XX at amniocentesis with high-level mosaicism for 45,X in a pregnancy with a favorable fetal outcome and postnatal decrease of the 45,X cell line.

A 20-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of the non-invasive prenatal testing (NIPT) result of -4.82 Z score in sex chromosome at 12 weeks of gestation suggestive of Turner syndrome in the fetus. Amniocentesis revealed a karyotype of 45,X [18]/46,XX [15], and simultaneous multiplex ligation-dependent probe amplification (MLPA) on the DNA extracted from uncultured amniocytes showed mosaic Turner syndrome. Prenatal ultrasound and parental karyotypes were normal. She was referred for genetic counseling at 24 weeks of gestation, and continuing pregnancy was encouraged. At 39 weeks of gestation, a 2550-g phenotypically normal female baby was delivered. The karyotypes of cord blood, umbilical cord and placenta were 45,X [24]/46,XX [16], 45,X [23]/46,XX [17] and 45,X [28]/46,X,del(X) (q23)[12], respectively. When follow-up at age two months, the neonate was phenotypically normal in development. The peripheral blood had a karyotypes of 45,X [16]/46,XX [24]. Interphase fluorescence in situ hybridization (FISH) analysis on 103 buccal mucosal cells showed normal disomy X signals in all cells.

High-level mosaicism for 45,X in 45,X/46, XX at amniocentesis can be associated with a favorable fetal outcome, cytogenetic discrepancy in various tissues, and postnatal decrease of the 45,X cell line.