A Case of Confined Placental Mosaicism with Trisomy 15 Associated with Turner Syndrome

INTRODUCTIONThe fetus and the placenta have the same chromosomal composition because of the same origin, zygote. Despite this, approximately l%-2% cytogenetic abnormality between CVS and placental tissue occurs (2, 7). This condition described as CPM, is explained as discrepancy between the chromosomal character of the placenta and fetal tissues (4). Differentiation of specific types of cells and tissues in the concepts begins at the early postferti 1 izational stages. If an error comprises at that stage, chromosomal mosaicism shows up. In addition to this the mosaic pattern depends on many factors, such as the number of blastomeres at the time of the mutational event, affected cell lineage, and cell viability and selection whether the zygote is chromosomally normal or abnormal (9). CPMs have three different types. Type 1 CPM; aneuploidy confined to cytotrophoblast, and thus is most often associated with normal pregnancy outcome. Type 2 CPM; the error occurs in a non-fetal cell of the inner cell mass. This trisomy is confined to the chorionic villus stroma, and thus normal pregnancy outcome or sometimes associated with delayed growth of the fetus. Type 3 CPM, aneuploid cell lines found in both cytotrophoblast and the villus stroma, but are absent in the embryo, and thus is associated with delayed growth in the fetus (5,6,8). At prenatal diagnosis process, when CVS mosaicism is determined, pregnant patients are counseled to medical geneticist and performed clinical examination and follow-up ultrasounds for congenital anomalies, and to offer amniocentesis or cord blood study to differentiate between CPM and true fetal karyotypic abnormality. Here, we report a case with high rate CPM mosaicism of trisomy 15 and true Turner syndrome.CASE REPORTA 29-year-old second gravida, non-consanguineous marriage presented at 12 weeks of gestation. She was healthy and had a healthy 3 year old male. The father was 32 year old, healthy. At 12 weeks she presented for genetic counseling secondary to ultrasound findings including increased fetal nuchal fold thickness and cystic hygroma. Due to ultrasound results CVS was done under ultrasound guidance for fetal karyotyping. The analysis of the long-term cultures of 45 metaphases had revealed mosaicism 45,X[20]/46,X, +15[25], After counselling, the couple decided to undergo termination of pregnancy. The fetus was terminated at 17 weeks and at the same time amniocentesis was performed and 45,X [20] was revealed. The foetal autopsy was done with the informed consent of the parents. The gross examination of the foetus showed phenotypic features of cystic hygroma, low seat ears, foetal scalp oedema and hemorrhage.I DISCUSSIONCPM is found in approximately 1-2% of pregnancies when CVS is performed in the first trimester (4), but about half of the cases of mosaicism are not found at term (6). According to the European Collaborative Research on Mosaicism in CVS (EUCROMIC, 1999) data, mosaic or true trisomy 15 is very rare and determined only %0.027 in all CVS (1). This case was associated with CPM of trisomy 15 in a histologically normal placenta at the same time Turner syndrome. To our knowledge, this is the first case described as Turner syndrome together with CPM of trisomy 15. But in medical literature, a fetus with mosaic trisomy 15 a rare karyotype of 47,XX, + 15/46,XX was reported (12).Three outcomes associated with CPM of trisomy 15 because of the cell type affected affects pregnancy. Firstly, the fetus has normal karyotype and the chromosomal abnormalities is limited to placental mosaicism, only intra uterine growth retardation ends up in fetus and stillbirth (6). Secondly, the fetus has true trisomy 15, so congenital anomalies of the fetus is common, especially cardiovascular and skeletal anomalies (3, 12). Finally, meiotic mosaicism often is associated with "trisomie rescue" whereby one of the extra chromosomes is expulsed and editing to a diploid karyotype. …