Prenatal detection of trisomy 9 mosaicism

Abstract

Chromosomal mosaicism in amniotic fluid cells poses a serious dilemma in prenatal diagnosis since the observation may represent: (1) pseudomosaicism--an inconsequential tissue culture artefact; or (2) true mosaicism--occurring in approximately 0.20 per cent of amniocenteses with a significant impact on pregnancy outcome. Mosaicism for trisomy 9 was observed in an amniotic fluid specimen obtained for advanced maternal age with two cell lines [46,XX (46 per cent)/47,XX, +9 (54 per cent)] present in each of four culture flasks. Since more than 75 per cent of newborns with trisomy 9 mosaicism have complex cardiac malformations, a fetal echocardiogram was obtained at 20 weeks' gestation and interpreted as normal. A fetal blood sample (22 weeks' gestation) disclosed only a single trisomy 9 cell among the 100 metaphases analysed. However, a second fetal echocardiogram performed at the time of blood sampling suggested a non-specific cardiac anomaly. Fetal autopsy following elective pregnancy termination revealed several malformations including severe micrognathia, persistence of the left superior vena cava, and skeletal anomalies. Cytogenetic studies of cell cultures derived from several fetal tissues demonstrated trisomy 9 ranging from 12 to 24 per cent.

Trisomy 9: Review and report of two new cases

“…Schwartz et al [1989] reported a case of mosaic trisomy 9 diagnosed by amniocentesis in which 46% of amniocytes, but only 1 of 50 fetal lymphocytes, were trisomic. In the case of Sherer et al [1992], trisomy 9 was identified by amniocentesis in all cells from all colonies and cultures, but no trisomy 9 cells were found in newborn cord or peripheral blood.…”

“…Four prenatally diagnosed cases which did not result in term birth were also reviewed and will be discussed, but were not included in the data analysis [Franke et al, 1975;Frohlich, 1982;Schwartz et al, 1989;Zadeh et al, 19871. Survival, gestational age at birth, parental ages, birth weight and head circumference, and incidence of various congenital anomalies were compared among mosaic and nonmosaic cases using chi-square analysis, Student's t-test, or Fisher's exact test where appropriate.…”

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Presenting physical characteristics, medical conditions, and developmental status of long‐term survivors with trisomy 9 mosaicism

“…Much of the available literature on trisomy 9 focuses on reports concerning results of prenatal testing including sonographic findings [e.g., Francke et al, 1975;Schwartz et al, 1989;Benacerraf et al, 1992;Saura et al, 1995] or fetal autopsy [Chitayat et al, 1995]. Schwartz et al [1989] describe the physical characteristics in a fetus with trisomy 9 mosaicism including micrognathia, skeletal malformations and cardiac malformations.…”

“…Schwartz et al [1989] describe the physical characteristics in a fetus with trisomy 9 mosaicism including micrognathia, skeletal malformations and cardiac malformations. Similar findings are found in a study by Smoleniec et al [1993] in a pregnancy that was electively terminated.…”