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Prenatal Diagnosis of Mosaic Tetrasomy 18p in a Case without Sonographic Abnormalities.

ABSTRACT: Small supernumerary marker chromosomes (sSMC) are still a major problem in clinical cytogenetics as they cannot be identified or characterized unambiguously by conventional cytogenetics alone. On the other hand, and perhaps more importantly in prenatal settings, there is a challenging situation for counseling how to predict the risk for an abnormal phenotype, especially in cases with a de novo sSMC. Here we report on the prenatal diagnosis of a mosaic tetrasomy 18p due to presence of an sSMC in a fetus without abnormal sonographic signs. For a 26-year-old, gravida 2 (para 1) amniocentesis was done due to consanguineous marriage and concern for Down syndrome, based on borderline risk assessment. Parental karyotypes were normal, indicating a de novo chromosome aberration of the fetus. FISH analysis as well as molecular karyotyping identified the sSMC as an i(18)(pter->q10:q10->pter), compatible with tetrasomy for the mentioned region. Cordocentesis was done due to normal sonography and the results from amniocentesis were confirmed. The parents opted for pregnancy termination and post mortem examination now noted, low anterior hairline, large philtrum, low-set posteriorly rotated malformed ears with prominent antihelix, lower limbs joint contracture and digital anomalies, including long and narrow toes with clinodactyly of the 1st and 5th toes and postaxial polydactyly of one hand. De novo i(18p) can be considered as a special case in the sense that the major relevant phenotypes mentioned for it, i.e. feeding difficulties, abnormalities in muscle tone and developmental/mental retardation, cognitive and behavioral characteristics, recurrent otitis media and seizures, are mostly postnatal. This emphasizes the necessity to determine the nature of a de novo euchromatic marker chromosome, especially in cases with normal ultrasound result and the suitability of a cordocentesis in order to better predicting the pregnancy outcome and parental counseling.

SUBMITTER: Karimzad Hagh J

PROVIDER: S-EPMC5568194 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Prenatal Diagnosis of Mosaic Tetrasomy 18p in a Case without Sonographic Abnormalities.

Karimzad Hagh Javad J Liehr Thomas T Ghaedi Hamid H Mossalaeie Mir Majid MM Alimohammadi Shohreh S Inanloo Hajiloo Faegheh F Moeini Zahra Z Sarabi Sadaf S Zare-Abdollahi Davood D

International journal of molecular and cellular medicine 20170117 1

Small supernumerary marker chromosomes (sSMC) are still a major problem in clinical cytogenetics as they cannot be identified or characterized unambiguously by conventional cytogenetics alone. On the other hand, and perhaps more importantly in prenatal settings, there is a challenging situation for counseling how to predict the risk for an abnormal phenotype, especially in cases with a <i>de novo</i> sSMC. Here we report on the prenatal diagnosis of a mosaic tetrasomy 18p due to presence of an s ...[more]

PMID: 28868271

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Project description:Partial tetrasomy of distal 13q has a reported association with a variable phenotype including microphthalmia, ear abnormalities, hypotelorism, facial dysmorphisms, urogenital defects, pigmentation and skin defects, and severe learning difficulties. A wide range of mosaicism has been reported, which may, to some extent, account for the variable spectrum of observed phenotypes. We report here a pregnancy conceived using intrauterine insemination in a 32-year-old female with a history of infertility. Non-invasive prenatal screening (NIPS) was performed in the first trimester which reported an increased risk for trisomy 13. Follow-up cytogenetic workup using chorionic villus sampling (CVS) and amniotic fluid samples showed a mosaic karyotype with a small supernumerary marker chromosome (sSMC). Chromosomal microarray analysis (CMA) identified a mosaic 31.34 Mb terminal gain on chr13q31.1q34 showing the likely origin of the sSMC to distal chromosome 13q. Follow-up metaphase FISH testing suggested an inverted duplication rearrangement involving 13q31q34 in the marker chromosome and the presence of a neocentromere. At 21 months of age, the proband has a history of gross motor delay, hypotonia, left microphthalmia, strabismus, congenital anomaly of the right optic nerve, hemangiomas, and a tethered spinal cord. Postnatal chromosome analyses in buccal, peripheral blood, and spinal cord ligament tissues were consistent with the previous amniocentesis and CVS findings, and the degree of mosaicism varied from 25 to 80%. It is often challenging to pinpoint the chromosomal identity of sSMCs using banding cytogenetics. A combination of low-pass genome sequencing of cell-free DNA, chromosomal microarray, and FISH enabled the identification of the precise chromosomal rearrangement in this patient. This study adds to the growing list of clinically identified neocentric marker chromosomes and is the first described instance of partial tetrasomy 13q31q34 identified in a mosaic state prenatally. Since NIPS is now being routinely performed along with invasive testing for advanced maternal age, an increased prenatal detection rate for mosaic sSMCs in otherwise normal pregnancies is expected. Future studies investigating how neocentromeres mediate gene expression changes could help identify potential epigenetic targets as treatment options to rescue or reverse the phenotypes seen in patients with congenital neocentromeres.

Project description:IntroductionUrorectal septum malformation sequence (URSMS) is a rare congenital abnormal syndrome that is caused by the incomplete division of the cloaca. Based on whether the cloaca membrane breaks down or not, the URSMS are classified as full and partial forms. The prenatal diagnosis of URSMS remains challenging because of poor recognition to this malformation and the relatively non-specific sonographic features. We report a prenatally sonographic diagnosed case of the partial URSMS, and review the literature to summarize the prenatal features.Case report and reviewA 37-year old woman was referred at 24 weeks of gestation for fetal abdominal cyst. Detailed sonographic examination was done and revealed the vesicocolic fistula, distended colon, absence of perianal hypoechoic ring, pyelectasis, and small stomach bubble. The URSMS was suspected.Amniocentesis was done and karyotyping revealed 46,XY. Furthermore, chromosomal microarray analysis (CMA) was performed for the first time in URSMS and an alteration of 111.8Kb deletion was detected in 16p13.3 which was located inside the RBFOX1 gene. Parental studies showed that the deletion was inherited from the father who has nomal clinical phenotype.The woman elected to terminate the pregnancy at 25 weeks gestation and postmortem examination confirmed the diagnosis of partial URSMS.The published studies were reviewed and 28 cases of URSMS with conducted prenatal ultrasonography were collected in this report. The most common sonographic description, as suspicious signs of URSMS, were severe oligohydramnios or anhydramnios, urinary tract anomalies, fetal intra-abdominal cysts, and dilated bowel. Also, enterolithiasis and vesicocolic fistula were relatively infrequent but highly specific feature of URSMS.ConclusionsURSMS is difficult to be diagnosed prenatally. However, it has characteristic features that can be detected by fetal ultrasonography, and a precise prenatal sonographic examination is crucial for diagnosing URSMS. Besides, more genomic profiling studies are needed to elucidate the causality.

Dataset Information

Prenatal Diagnosis of Mosaic Tetrasomy 18p in a Case without Sonographic Abnormalities.

Publications

Prenatal Diagnosis of Mosaic Tetrasomy 18p in a Case without Sonographic Abnormalities.

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