Prenatal diagnosis of a trisomy 7 mosaic case: CMA, CNV-seq, karyotyping, interphase FISH, and MS-MLPA, which technique to choose?

OBJECTIVE: This study aims to perform a prenatal genetic diagnosis of a high-risk fetus with trisomy 7 identified by noninvasive prenatal testing (NIPT) and to evaluate the efficacy of different genetic testing techniques for prenatal diagnosis of trisomy mosaicism. METHODS: For prenatal diagnosis of a pregnant woman with a high risk of trisomy 7 suggested by NIPT, karyotyping and chromosomal microarray analysis (CMA) were performed on an amniotic fluid sample. Low-depth whole-genome copy number variation sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) were used to clarify the results further. In addition, methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) was performed to analyze the possibility of uniparental disomy(UPD). RESULTS: Amniotic fluid karyotype analysis revealed a 46, XX result. Approximately 20% mosaic trisomy 7 was detected according to the CMA result. About 16% and 4% of mosaicism was detected by CNV-seq and FISH, respectively. MS-MLPA showed no methylation abnormalities. The fetal ultrasound did not show any detectable abnormalities except for mild intrauterine growth retardation seen at 39 weeks of gestation. After receiving genetic counseling, the expectant mother decided to continue the pregnancy, and follow-up within three months of delivery was normal. CONCLUSION: In high-risk NIPT diagnosis, a combination of cytogenetic and molecular genetic techniques proves fruitful in detecting low-level mosaicism. Furthermore, the exclusion of UPD on chromosome 7 remains crucial when NIPT indicates a positive prenatal diagnosis of trisomy 7.

Novel Autopsy Findings in Premature Infant With Beckwith-Wiedemann Syndrome Uniparental Disomy: Multifocal Developmental Dysplastic Chrondromatous Lesions and Cortical Neuronal Heterotopias.

BACKGROUND: Beckwith-Wiedemann syndrome (BWS) is an overgrowth disorder that exhibits etiologic genomic imprinting characterized by molecular heterogeneity and phenotypic variability. Associations with localized developmental dysplastic chondromatous lesions and cortical neuronal heterotopias have not previously been described. CASE PRESENTATION: A 33-week gestational age female had an omphalocele and intractable hypoglycemia at birth. The placenta demonstrated placental mesenchymal dysplasia. Detection of hypermethylation of IC1 and hypomethylation of IC2 confirmed Beckwith-Wiedemann syndrome, most likely due to uniparental disomy. Additional findings included right mid-tibial and right 5-8th developmental dysplastic chondromatous lesions, absent corpus callosum and numerous right-sided cortical neuronal heterotopias, right hemihypertrophy, multiple cystic hepatic mesenchymal hamartomas and hepatic infantile hemangiomas, nisidioblastosis and cystic pancreatic lesions. The infant died with multi-organ failure and anasarca at 7 weeks of life. CONCLUSION: Beckwith-Wiedemann syndrome anomalies may include multifocal developmental dysplastic chondromatous lesions and cerebral neuronal heterotopias, lateralized, and corpus callosum aplasia.

Prenatal detection of mosaicism for a genome wide uniparental disomy cell line in a cohort of patients: Implications and outcomes.

OBJECTIVES: To investigate the prenatal detection rate of mosaicism by SNP microarray analysis, in which an individual has not one, but two, complete genomes (sets of DNA) in their body, a normal biparental line with a Genome Wide Uniparental Disomy (GWUPD) cell line was used. METHODS: This study retrospectively examines the prenatal detection of GWUPD in a cohort of ∼90,000 prenatal specimens and ∼20,000 products of conceptions (POCs) that were studied by SNP microarray. RESULTS: In total, 25 cases of GWUPD were detected; 16 cases were detected prenatally with GWUPD (∼0.018%) and 9 POCs revealed GWUPD (0.045%). The nine POC specimens presented with placental abnormalities. The 12 amniotic fluid specimens were ascertained because of abnormal ultrasound findings. Nine of 12 pregnancies had findings consistent with Beckwith-Wiedemann syndrome or because of abnormal placentas. However, three pregnancies were detected with GWUPD of maternal origin, with less common findings and demonstrated maternal origin. Four other pregnancies showed GWUPD in a chorionic villus sample, but normal findings in amniotic fluid and apparently normal fetal development. CONCLUSIONS: This cohort with GWUPD mosaicism expands our understanding of GWUPD and has implications for prenatal care and counseling. Additional studies are necessary to understand the rarer maternal GWUPD.

Effect of uniparental disomy in parentage testing.

Uniparental disomy (UPD) is a rare type of chromosomal aberration that may hinder the analysis of kinship during forensic identification. Here, we investigated these genetic findings to avoid false exclusions during parentage testing. Thirty-nine fluorescently labeled, autosomal short tandem repeats (STR) were amplified in three cases, to detect parent-child relationships. Twenty-three fluorescently labeled Y-chromosome STRs were also employed. These were subjected to capillary electrophoresis. The parentage index was calculated by the bipartite or tripartite model. Single nucleotide polymorphism (SNP) microarrays were performed to further investigate the genetic mechanisms. The conclusions supported the biological mother-child relationship in three cases. However, in all cases, the alleged father and child had three autosomal STR markers, constrained to a single chromosome, which did not conform to Mendelian inheritance rules. The genotyping of 23 Y-chromosome STRs did not reveal any violations of Mendelian law. The combination of STR profiling and SNP microarrays suggested that two children had maternal UPD of chromosome 7, whilst one had UPD of chromosome 2. After excluding the three incompatible loci, the conclusions supported the biological father-child relationship in all cases. The same results were obtained when parentage testing of trios was used. Uniparental disomy may complicate the judgment of kinship in parentage testing. The possibility of UPD should be considered when incompatible STR loci are found on the same chromosome. Genetic evidence obtained through additional molecular techniques can provide better interpretation of kinship in the presence of UPD and avoid false exclusions of biological relationships.

SNP chromosome microarray genotyping for detection of uniparental disomy in the clinical diagnostic laboratory.

Single nucleotide polymorphism (SNP) chromosome microarray is well established for investigation of children with intellectual deficit/development delay and prenatal diagnosis of fetal malformation but has also emerged for uniparental disomy (UPD) genotyping. Despite published guidelines on clinical indications for testing there are no laboratory guidelines published for performing SNP microarray UPD genotyping. We evaluated SNP microarray UPD genotyping using Illumina beadchips on family trios/duos within a clinical cohort (n=98) and then explored our findings in a post-study audit (n=123). UPD occurred in 18.6% and 19.5% cases, respectively, with chromosome 15 most frequent (62.5% and 25.0%). UPD was predominantly maternal in origin (87.5% and 79.2%), highest in suspected genomic imprinting disorder cases (56.3% and 41.7%) but absent amongst children of translocation carriers. We assessed regions of homozygosity among UPD cases. The smallest interstitial and terminal regions were 2.5 Mb and 9.3 Mb, respectively. We found regions of homozygosity confounded genotyping in a consanguineous case with UPD15 and another with segmental UPD due to non-informative probes. In a unique case with chromosome 15q UPD mosaicism, we established the detection limit of mosaicism as ∼5%. From the benefits and pitfalls identified in this study, we propose a testing model and recommendations for UPD genotyping by SNP microarray.

Prenatal diagnosis of mosaic trisomy 18 and maternal uniparental disomy 18 by amniocentesis in a pregnancy associated with cytogenetic discrepancy in various tissues and a favorable fetal outcome.

OBJECTIVE: We present prenatal diagnosis of mosaic trisomy 18 and maternal uniparental disomy (UPD) 18 in a pregnancy with a favorable fetal outcome. CASE REPORT: A 34-year-old woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age, and the result was 47,XY,+18 [4]/46,XY [25] in cultured amniocytes. Simultaneous array comparative genomic hybridization (aCGH) on uncultured amniocytes revealed 65% mosaicism for trisomy 18. Prenatal ultrasound was normal. She consulted our hospital and underwent repeat amniocentesis at 22 weeks of gestation, and the result revealed a karyotype of 47,XY,+18 [9]/46,XY [12] in cultured amniocytes. Simultaneous aCGH on uncultured amniocytes revealed arr 18p11.32q23 × 2.4 (log2 ratio = 0.3) consistent with 40% mosaicism for trisomy 18. Parental karyotypes were normal. Quantitative fluorescent polymerase chain reaction (QF-PCR) analysis on the DNA extracted from parental bloods and uncultured amniocytes confirmed maternal uniparental heterodisomy of chromosome 18. At 26 weeks of gestation, she underwent the third amniocentesis which revealed a karyotype of 47,XY,+18 [7]/46,XY [19] in cultured amniocytes. Simultaneous aCGH on uncultured amniocytes revealed arr 18p11.32q23 × 2.4 (log2 ratio = 0.27) consistent with 40% mosaicism for trisomy 18. Interphase fluorescence in situ hybridization (FISH) on uncultured amniocytes revealed 38% (38/100 cells) mosaicism for trisomy 18. The woman was advised to continue the pregnancy, and a 2620-g phenotypically normal male baby was delivered at 40 weeks of gestation. At birth, the karyotypes of cord blood, umbilical cord and placenta were 47,XY,+18 [14]/46,XY [26], 47,XY,+18 [9]/46,XY [31] and 47,XY,+18 (40/40 cells), respectively. When follow-up at age 2½ months, the neonate was phenotypically normal. The peripheral blood had a karyotype of 47,XY,+18 [28]/46,XY [12], and interphase FISH analysis on buccal mucosal cells detected 6.4% (7/93 cells) mosaicism for trisomy 18, compared with 0% (0/100 cells) in the normal control. When follow-up at age seven months, the neonate was normal in development, and the peripheral blood had a karyotype of 47,XY,+18 [18]/46,XY [22]. CONCLUSIONS: Mosaic trisomy 18 at amniocentesis can be associated with cytogenetic discrepancy in various tissues, UPD 18 and a favorable fetal outcome. Prenatal diagnosis of mosaic trisomy 18 should alert the possibility of UPD 18 and include UPD testing.

A Case of Maternal Uniparental Disomy of Chromosome 6 with Intrauterine Growth Restriction.

Background: Uniparental disomy (UPD) is a well-known epigenomic anomaly characterized by the inheritance of both copies of a homologous pair of chromosomes (or part thereof) from the same parent. This genetic condition can have significant implications for prenatal diagnosis and management. Case Presentation: We present a case of a 29-year-old gravida 1 para 0 female who underwent amniocentesis at pregnancy Week 19 due to a high possibility of trisomy chromosome 6, as indicated by noninvasive prenatal testing (NIPT). However, fluorescence in situ hybridization (FISH) and whole-exome sequencing (WES) revealed no abnormalities. Subsequently, chromosomal microarray analysis (CMA) detected uniparental disomy of chromosome 6. Additionally, an ultrasound examination at 28 weeks of gestation revealed intrauterine growth restriction (IUGR). Given these findings, the parents made the decision to terminate the pregnancy. Conclusions: The combination of genetic counseling, FISH, karyotype analysis, WES, CMA, NIPT, and prenatal ultrasound can provide valuable insights for the prenatal diagnosis of UPD. These diagnostic approaches play a crucial role in identifying and managing cases of UPD, primarily when associated with intrauterine growth restrictions.

Low-level mosaic trisomy 9 at amniocentesis associated with a positive non-invasive prenatal testing for trisomy 9, maternal uniparental disomy 9, intrauterine growth restriction and a favorable fetal outcome in a pregnancy.

OBJECTIVE: We present low-level mosaic trisomy 9 at amniocentesis associated with a positive non-invasive prenatal testing (NIPT) for trisomy 9, maternal uniparental disomy (UPD) 9, intrauterine growth restriction (IUGR) and a favorable fetal outcome in a pregnancy. CASE REPORT: A 41-year-old, gravida 3, para 0, woman underwent amniocentesis at 18 weeks of gestation because of NIPT at 10 weeks of gestation suspicious of trisomy 9 in the fetus. This pregnancy was conceived by in vitro fertilization (IVF). Amniocentesis revealed a karyotype of 47,XY,+9 [2]/46,XY[23]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed arr (1-22) × 2, (X,Y) × 1 and detected no genomic imbalance. Polymorphic DNA marker analysis showed maternal uniparental heterodisomy 9 in the amniocytes. Prenatal ultrasound was normal. The woman was referred for genetic counseling at 22 weeks of gestation. The soluble fms-like tyrosine kinase (sFlt)/placental growth factor (PlGF) = 13.1 (normal < 38). There was no gestational hypertension. Continuing the pregnancy was advised. No repeat amniocentesis was performed because of persistent irregular contractions. IUGR was noted. A 2156-g phenotypically normal baby was delivered at 37 weeks of gestation. The cord blood and umbilical cord had a karyotype of 46,XY (40/40 cells). The placenta had a karyotype of 47,XY,+9 (40/40 cells). The parental karyotypes were normal. Quantitative fluorescence polymerase chain reaction (QF-PCR) on the DNA extracted from parental bloods, cord blood, umbilical cord and placenta revealed maternal uniparental heterodisomy 9 in cord blood and umbilical cord, and trisomy 9 of maternal origin in placenta. When follow-up at age three months, the neonate was normal in development and phenotype. The buccal mucosal cells had 3% (3/101 cells) mosaicism for trisomy 9 by interphase fluorescent in situ hybridization (FISH) analysis. CONCLUSION: Mosaic trisomy 9 at prenatal diagnosis should alert the possibility of UPD 9 and include a UPD 9 testing. Low-level mosaic trisomy 9 at amniocentesis can be associated with UPD 9 and a favorable fetal outcome.

Low-level mosaic trisomy 20 without uniparental disomy 20 at amniocentesis in a pregnancy associated with a favorable outcome, cytogenetic discrepancy between uncultured amniocytes and cultured amniocytes and perinatal progressive decrease of the aneuploid cell line.

OBJECTIVE: We present low-level mosaic trisomy 20 without uniparental disomy (UPD) 20 at amniocentesis in a pregnancy associated with a favorable outcome, cytogenetic discrepancy between uncultured amniocytes and cultured amniocytes and perinatal progressive decrease of the aneuploid cell line. CASE REPORT: A 36-year-old, gravida 2, para 1, woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+20[3]/46,XY[17]. Array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (1-22) × 2, X × 1, Y × 1 with no genomic imbalance. Prenatal ultrasound was unremarkable. She was referred for genetic counseling at 23 weeks of gestation, and repeat amniocentesis was performed. Cytogenetic analysis of the cultured amniocytes revealed a karyotype of 47,XY,+20[1]/46,XY[27]. Simultaneous aCGH analysis on the DNA extracted from uncultured amniocytes by SurePrint G3 Unrestricted CGH ISCA v2, 8 × 60 K (Agilent Technologies, CA, USA) revealed the result of arr (1-22) × 2, X × 1, Y × 1. Quantitative fluorescent polymerase chain reaction (QF-PCR) assays on the DNAs extracted from uncultured amniocytes and parental bloods excluded UPD 20. The woman was advised to continue the pregnancy, and a healthy 3750-g phenotypically normal male baby was delivered at 38 weeks of gestation. The cord blood had a karyotype of 46,XY (40/40 cells). CONCLUSION: Low-level mosaic trisomy 20 without UPD 20 at amniocentesis can be associated with a favorable outcome. Progressive decrease of the aneuploid cell line can occur in mosaic trisomy 20 at amniocentesis. Low-level mosaic trisomy 20 at amniocentesis can be a transient and benign condition.

Low-level mosaic double trisomy involving trisomy 6 and trisomy 20 (48,XY,+6,+20) at amniocentesis without uniparental disomy (UPD) 6 and UPD 20 in a pregnancy associated with a favorable outcome.

OBJECTIVE: We present low-level mosaic double trisomy involving trisomy 6 and trisomy 20 (48,XY,+6,+20) at amniocentesis without uniparental disomy (UPD) 6 and UPD 20 in a pregnancy associated with a favorable outcome. CASE REPORT: A 38-year-old woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 48,XY,+6,+20[2]/46,XY[15]. Repeat amniocentesis at 20 weeks of gestation revealed a karyotype of 48,XY,+6,+20[6]/46,XY[43], and simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (X,Y) × 1, (1-22) × 2 with no genomic imbalance. At 22 weeks of gestation, the woman underwent cordocentesis which revealed karyotype of 46,XY (60/60 cells). At 26 weeks of gestation, the woman underwent the third amniocentesis which revealed a karyotype of 48,XY,+6,+20[5]/46,XY[30], and simultaneous aCGH analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (1-22) × 2, X × 1, Y × 1 without genomic imbalance. The parental karyotypes and prenatal ultrasound were normal. Polymorphic marker analysis using the DNAs extracted from uncultured amniocytes and parental bloods excluded UPD 6 and UPD 20. Interphase fluorescence in situ hybridization (FISH) analysis on 100 uncultured amniocytes detected double trisomy 6 and trisomy 20 in 10 cells, consistent with 10% (10/100 cells) mosaicism for double trisomy 6 and trisomy 20. The woman was encouraged to continue the pregnancy, and a phenotypically normal 3328-g male baby was delivered at 38 weeks of gestation. The cord blood, umbilical cord and the placenta had a karyotype of 46,XY (40/40 cells). CONCLUSION: Low-level mosaic double trisomy involving trisomy 6 and trisomy 20 at amniocentesis without UPD 6 and UPD 20 can be associated with a favorable fetal outcome.

Mosaic trisomy 21 at amniocentesis in a twin pregnancy associated with a favorable fetal outcome, maternal uniparental disomy 21 and postnatal decrease of the trisomy 21 cell line.

OBJECTIVE: We present mosaic trisomy 21 at amniocentesis in a twin pregnancy associated with a favorable fetal outcome, maternal uniparental disomy (UPD) 21 and postnatal decrease of the trisomy 21 cell line. CASE REPORT: A 36-year-old woman underwent elective amniocentesis at 16 weeks of gestation because of advanced maternal age, and an abnormal non-invasive prenatal testing (NIPT) result suggesting trisomy 21. Amniocentesis revealed the karyotype of 46, XX in co-twin A and the karyotype of 47,XY,+21[12]/46,XY[21] in co-twin B in the cultured amniocytes by in situ culture method. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr (21) × 3 [0.40] in co-twin B, consistent with 40% mosaicism for trisomy 21. Prenatal ultrasound was unremarkable, and the parental karyotypes were normal. Following genetic counseling, the parents decided to continue the pregnancy. At 36 weeks of gestation, a 2140-g female co-twin A and a 1800-g male co-twin B were delivered without any phenotypical abnormality. The karyotypes of the umbilical cord and placenta of co-twin B were 47,XY,+21[16]/46,XY[24] and 47,XY,+21 (40/40 cells), respectively. Quantitative fluorescence polymerase chain reaction (QF-PCR) analysis on the DNA extracted from parental bloods and umbilical cord, cord blood and placenta and peripheral blood at age five months of co-twin B confirmed a maternal origin of trisomy 21 and maternal uniparental isodisomy 21. aCGH analysis on the cord blood revealed the result of arr 21q11.2q22.3 × 2.25 consistent with 20%-25% (log2 ratio = 0.15-0.2) mosaicism for trisomy 21. When follow-up at age five months, the co-twin B was phenotypically normal. His peripheral blood had a karyotype of 47,XY,+21[3]/46,XY[37]. Interphase fluorescence in situ hybridization (FISH) on 100 buccal mucosal cells detected no trisomy 21 signals. The peripheral blood had uniparental isodisomy 21. CONCLUSION: Mosaic trisomy 21 at amniocentesis can be a transient and benign condition and should alert the possibility of UPD 21. The abnormal trisomy 21 cell line in mosaic trisomy 21 at amniocentesis may decrease and disappear after birth.

Late amniocentesis with uniparental disomy testing following successful in vitro fertilization and transfer of three mosaic embryos in a pregnancy with a favorable outcome.

OBJECTIVE: We present late amniocentesis with the application of uniparental disomy (UPD) testing following successful in vitro fertilization (IVF) and transfer of three mosaic embryos in a pregnancy with a favorable outcome. CASE REPORT: A 41-year-old, gravida 2, para 0, woman underwent late amniocentesis at 28 weeks of gestation because of advanced maternal age. The pregnancy was conceived by IVF and transfer of three mosaic embryos, i.e., one embryo with mosaic trisomies 20 and 2, one embryo with mosaic partial trisomies 9 and 3 and one embryo with partial trisomies 11 and 17. First-trimester non-invasive prenatal testing (NIPT) and fetal ultrasound revealed no abnormal findings. Late amniocentesis revealed a karyotype of 46,XY. Array comparative genomic hybridization (aCGH) revealed the result of arr [GRCh37] (X,Y) × 1, (1-22) × 2. Polymorphic DNA marker analysis using the DNAs extracted from the uncultured amniocytes and parental bloods excluded UPD 20. At 38 weeks of gestation, a healthy 3010-g male baby was delivered with no phenotypic abnormalities. CONCLUSION: Prenatal diagnosis of normal karyotype following mosaic embryo transfer should include UPD testing if necessary.

Pigmentary mosaicism as a recurrent clinical manifestation in three new patients with mosaic trisomy 12 diagnosed postnatally: cases report and literature review.

BACKGROUND: To date, only twenty-one cases diagnosed postnatally with mosaic trisomy 12 have been reported. The most frequent phenotypic manifestations are developmental delay, dysmorphic facial features, congenital heart defects, digital alterations, and pigmentary disorders. In the present report, detailed clinical and genetic profiles of three unrelated new patients with mosaic trisomy 12 are described and compared with previously reported cases. CASE PRESENTATION: In the present report, we include the clinical, cytogenetic, and molecular description of three Mexican patients diagnosed postnatally with mosaic trisomy 12. At phenotypic level, the three patients present with developmental delay, dysmorphic facial features, congenital heart defects and skin pigmentary anomalies. Particularly, patient 1 showed unique eye alterations as bilateral distichiasis, triple rows of upper lashes, and digital abnormalities. In patient 2 redundant skin, severe hearing loss, and hypotonia were observed, and patient 3 presented with hypertelorism and telecanthus. Hyperpigmentation with disseminated pigmentary anomalies is a common trait in all of them. The cytogenetic study was carried out under the strict criteria of analysis, screening 50-100 metaphases from three different tissues, showing trisomy 12 mosaicism in at least one of the three different tissues analyzed. With SNParray, the presence of low-level mosaic copy number variants not previously detected by cytogenetics, and uniparental disomy of chromosome 12, was excluded. STR markers allowed to confirm the absence of uniparental disomy as well as to know the parental origin of supernumerary chromosome 12. CONCLUSIONS: The detailed clinical, cytogenetic, and molecular description of these three new patients, contributes with relevant information to delineate more accurately a group of patients that show a heterogeneous phenotype, although sharing the same chromosomal alteration. The possibility of detecting mosaic trisomy 12 is directly associated with the sensitivity of the methodology applied to reveal the low-level chromosomal mosaicism, as well as with the possibility to perform the analysis in a suitable tissue.

Prenatal Diagnosis and Fetal Outcome with Mosaic Genome-Wide Uniparental Disomy.

INTRODUCTION: While non-mosaic genome-wide paternal uniparental disomy (patUPD) is consistent with complete hydatidiform mole, the prenatal presentation of mosaic genome-wide patUPD is not well defined. This report adds another case to the small cohort of patients with the rare genetic disorder of mosaic genome-wide patUPD and provides one of the few examples of a prenatal presentation of this disease. We discuss ultrasound findings and prenatal analysis to review predominant genetic and clinical features associated with mosaic genome-wide patUPD. CASE PRESENTATION: A 30-year-old gravida 1 para 0 woman was referred at 10 weeks gestation due to an abnormal first-trimester ultrasound suggesting a partial molar pregnancy. The patient undertook genetic counseling and reviewed possible genetic etiologies and testing options. Karyotype analysis demonstrated a female fetus (46, XX). The BWS methylation pattern suggested the absence of maternally derived copies of IC1 (H19) and IC2 (LIT1) critical regions, which could result from patUPD of chromosome 11. CMA of cultured amniocytes was significant for arr(1-22,X)x2 hmz, consistent with genome-wide absence of heterozygosity (shown in Fig. 3). DISCUSSION/CONCLUSION: This case report is intended to add to the limited knowledge regarding prenatal diagnosis of mosaic genome-wide patUPD by highlighting the ultrasound findings, the genetic testing performed, and fetal outcome. The fetal karyotype was normal. CMA was consistent with a molecular diagnosis of GWUPD. Low-level mosaicism in our sample was inferred given the clinical presentation of a developing fetus. Methylation studies were consistent with a diagnosis of BWS. The diagnosis of genome-wide patUPD using CMA provides further knowledge of UPD and its functional relevance. In a prenatal setting, a CMA profile without heterozygosity is typical of a complete molar pregnancy. However, in the presence of a fetus, it likely represents mosaic GWUPD, a rare condition that is usually of paternal origin.

Cytogenetic discrepancy between uncultured amniocytes and cultured amniocytes in mosaic trisomy 15 at amniocentesis in a pregnancy with a favorable outcome.

OBJECTIVE: We present prenatal diagnosis of mosaic trisomy 15 in a pregnancy with a favorable outcome. CASE REPORT: A 33-year-old, primigravid woman underwent amniocentesis at 19 weeks of gestation because non-invasive prenatal testing (NIPT) revealed gene dosage increase at chromosome 15. Cytogenetic analysis revealed a karyotype of 47,XX,+15[10]/46,XX[13]. Using uncultured amniocytes, array comparative genomic hybridization (aCGH) revealed arr [GRCh37] (X) × 2, (15) × 3 [0.75], multiplex ligation-dependent probe amplification (MLPA) analysis showed rsa [GRCh36] 15q11q13 (21,362,818-27,196,819) × 3 [0.76] and methylation-specific (MS)-MLPA analysis showed a methylation index = 0.41 with paternal gene dosage increase at 15q11-q13. Repeat amniocentesis at 25 weeks of gestation revealed a karyotype of 47,XX,+15[6]/46,XX[14]. Using uncultured amniocytes, quantitative fluorescent polymerase chain reaction (QF-PCR) assays excluded uniparental disomy (UPD) 15 and determined a paternal origin of the extra chromosome 15, aCGH analysis showed 75%-80% mosaicism for trisomy 15, and interphase fluorescence in situ hybridization (FISH) showed 45.5% (46/101 cells) mosaicism for trisomy 15. Repeat amniocentesis at 28 weeks of gestation revealed a karyotype of 47,XX,+15[2]/46,XX[23]. Using uncultured amniocytes, aCGH showed 75-80% mosaicism for trisomy 15, and FISH showed 70.6% (72/102 cells) mosaicism for trisomy 15. Using cultured amniocytes, QF-PCR assays excluded UPD 15. Cordocentesis at 30 weeks of gestation revealed a karyotype of 47,XX,+15[2]/46,XX[138]. Using cord blood, aCGH revealed 9% gene dosage increase at chromosome 15, and MS-MLPA analysis excluded UPD 15. At 36 weeks of gestation, a 2060-g phenotypically normal baby was delivered. The cord blood had 46, XX (40/40 cells). The placenta had 47,XX,+15 (40/40 cells). QF-PCR analysis on placenta showed a paternal origin of trisomy 15. FISH analysis on buccal mucosal cells at age 20 days showed 20% (20/100 cells) mosaicism for trisomy 15. CONCLUSION: Cytogenetic discrepancy may occur between uncultured and cultured amniocytes in mosaic trisomy 15 at amniocentesis. Cultured amniocytes may present progressive decrease in the levels of mosaicism for trisomy 15 as the fetus grows. Mosaic trisomy 15 at amniocentesis without UPD 15 can be associated with a favorable outcome.

Cytogenetic discrepancy between uncultured amniocytes and cultured amniocytes in mosaic trisomy 18 at amniocentesis in a pregnancy with a favorable fetal outcome and maternal uniparental disomy 18.

OBJECTIVE: We present prenatal diagnosis of mosaic trisomy 18 in a pregnancy with a favorable fetal outcome and maternal uniparental disomy 18. CASE REPORT: A 38-year-old, primigravid woman underwent the first amniocentesis at 16 weeks of gestation because advanced maternal age. Amniocentesis revealed a karyotype of 46,XX [22/22] in cultured amniocytes, and 36% mosaicism for trisomy 18 and a maternally inherited Xp22.31 microdeletion by array comparative genomic hybridization (aCGH) in uncultured amniocytes. The second amniocentesis at 18 weeks of gestation revealed 47,XX,+18 [14]/46,XX [36] in cultured amniocytes and 36% mosaicism for trisomy 18 by multiplex ligation-dependent probe amplification (MLPA) P095 in cultured amniocytes. Prenatal ultrasound was normal. The parents were phenotypically normal. The third amniocentesis at 23 weeks of gestation revealed 47,XX,+18 [3]/46,XX [17] in cultured amniocytes, and in uncultured amniocytes, aCGH revealed 45%-50% mosaicism for trisomy 18, interphase fluorescence in situ hybridization (FISH) revealed 36% (36/100 cells) mosaicism for trisomy 18, and quantitative fluorescent polymerase chain reaction (QF-PCR) showed mosaic maternal uniparental heterodisomy for chromosome 18 and mosaic trisomy 18 of maternal origin. The fourth amniocentesis at 32 weeks of gestation revealed a karyotype of 46,XX [20/20] in cultured amniocytes, and in uncultured amniocytes, aCGH revealed 50%-60% mosaicism for trisomy 18, FISH revealed 21.8% (22/101 cells) mosaicism for trisomy 18, and non-invasive prenatal testing (NIPT) showed chromosome 18 gene dosage increase in the maternal blood. At 34 weeks of gestation, a 1480-g phenotypically normal baby was delivered. The cord blood had 47,XX,+18 [10]/46,XX [30]. The umbilical cord had 47,XX,+18 [4]/46,XX [36]. The placenta had 47,XX,+18 [40/40], and QF-PCR analysis confirmed trisomy 18 of maternal origin. When follow-up at age four months, the neonate was phenotypically normal, FISH analysis on buccal mucosal cells revealed 2% (2/100 cells) mosaicism for trisomy 18, and the peripheral blood had 47,XX,+18 [18]/46,XX [22]. When follow-up at age eight months, the neonate had normal development, the peripheral blood had 47,XX,+18 [15]/46,XX [25], and the buccal mucosal cells showed maternal uniparental heterodisomy for chromosome 18. CONCLUSION: Cytogenetic discrepancy may occur between uncultured and cultured amniocytes in mosaic trisomy 18 at amniocentesis. Cultured amniocytes may present progressive decrease in the levels of mosaicism for trisomy 18 as the fetus grows. Mosaic trisomy 18 at amniocentesis can be associated with a favorable outcome.

Prenatal diagnosis and genetic counseling of uniparental disomy.

Uniparental disomy (UPD) is the inheritance of both homologous chromosomes from a single parent. Most chromosomes involving UPD have no pathogenic effects. However, abnormal phenotypes in cases with UPD can be mainly caused by disrupting genetic imprinting and by uncovering harmful autosomal recessive mutations. The documented phenotypes of UPD associated with imprinted genes include maternal UPD for chromosomes 7, 11, 14, 15, 16, and 20, and paternal UPD for chromosomes 6, 11, 14, 15, and 20. Prenatal awareness of UPD is important to provide accurate genetic counseling and prenatal UPD test is suggested when abnormal fetal ultrasound with suspicious phenotypes for UPD syndromes caused by genetic imprinting disorders or presence of chromosomal aberrations involving the imprinted chromosomes.