Prenatal diagnosis and molecular cytogenetic characterization of mosaic ring chromosome 21 associated with low PAPP-A and low PlGF in the first-trimester maternal serum screening

ObjectiveWe present diagnosis and molecular cytogenetic characterization of mosaic ring chromosome 21 [r(21)].Case reportA 17-year-old, gravida 2, para 1, woman underwent amniocentesis at 17 weeks of gestation because of an abnormal result of the first-trimester maternal serum screening for Down syndrome with a free β-hCG level of 1.736 multiples of the median (MoM), a pregnancy associated plasma protein-A (PAPP-A) level of 0.275 MoM, a placental growth factor (PlGF) level of 0.281 MoM, a Down syndrome risk of 1:222 and a preeclampsia risk of 1:175. Cytogenetic analysis of cultured amniocytes revealed the result of 46,XX,r(21) (p12q22.3)[19]/45,XX,-21[13]. Array comparative genomic hybridization (aCGH) analysis of cultured amniocytes revealed the result of arr [GRCh37] 21q11.2q22.2 (15,485,008–40,625,594) × 1～2, 21q22.2q22.3 (40,703,792–46,682,184) × 2～3, 21q22.3 (46,761,631–48,084,156) × 1, consistent with mosaic monosomy 21 and r(21) (p12q22.3). The pregnancy was subsequently terminated, and a malformed fetus was delivered with low-set ears and hypotelorism. Postnatal cytogenetic analysis revealed a karyotype of 46,XX,r(21) (p12q22.3)[30]/45,XX,-21[8]/46,XX,idic r(21) (p12q22.3)[2] in the cord blood, 46,XX,r(21) (p12q22.3)[34]/45,XX,-21[6] in the skin, 46,XX,r(21) (p12q22.3)[37]/45,XX,-21[3] in the umbilical cord and 46,XX,dup(21) (q22.2q22.3)[32]/46,XX,r(21) (p12q22.3)[8] in the placenta. aCGH analysis of cord blood revealed the result of arr 21q11.2q22.2 (15,499,847–40,662,581) × 2.3, arr 21q22.2q22.3 (40,703,792–46,682,184) × 3.6, arr 21q22.3 (46,761,632–48,090,317) × 1, consistent with mosaic duplication of 21q11.2-q22.2 and 21q22.2-q22.3, and a 1.33-Mb 21q22.3 deletion encompassing the genes of COL18A1, SLC19A1, PCBP3, COL6A1, COL6A2, FTCD, LSS, MCM3AP, YBEY, PCNT, DIP2A, S100B and PRMT2.ConclusionMosaic r(21) at amniocentesis may be associated with monosomy 21, idic r(21) and dup(21), and low PAPP-A and low PlGF in the first-trimester maternal serum screening.     

Detection of a familial 21q22.3 microduplication in a fetus associated with congenital heart defects

ObjectiveWe present a familial 21q22.3 microduplication in a fetus associated with prenatally detected congenital heart defects (CHD).Case reportA 38-year-old woman underwent amniocentesis at 22 weeks of gestation because of sonographic findings of double outlet of right ventricle, ventricular septal defect and transposition of great artery in the fetus. Her husband was 42 years old, and there was no CHD and congenital malformation in the family. Cytogenetic analysis revealed a karyotype of 46,XY in the fetus. Simultaneous array comparative genomic hybridization (aCGH) analysis using uncultured amniocytes revealed a 0.56-Mb microduplication of 21q22.3 or arr 21q22.3 (47,482,210-48,043,704)×3.0 [GRCh37 (hg19)] encompassing nine Online Mendelian Inheritance in Man (OMIM) genes of FTCD, SPATC1L, LSS, MCM3AP, YBEY, PCNT, DIP2A, S100B and PRMT2. aCGH analysis of the parental bloods revealed that the phenotypically normal father carried the same microduplication. The parents decided to continue the pregnancy, and a 3168-g male baby was delivered at term without Down syndrome phenotype except CHD. Mutational analysis of the CRELD1 gene on the DNA extracted from the cord blood showed no mutation in CRELD1. Postnatal molecular cytogenetic analysis of the cord blood confirmed the prenatal diagnosis. The infant underwent a successful heart surgery to correct the CHD and was doing well without psychomotor or developmental delay at six months of age.ConclusionPrenatal diagnosis of 21q22.3 microduplication associated with CHD should include a differential diagnosis of Down syndrome.     

Cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes in mosaic 46,XX,dup(9)(q22.3q34.1)/46,XX at amniocentesis in a pregnancy with a favorable outcome

ObjectiveWe present our observation of cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes in mosaic dup(9)(q22.3q34.1) at amniocentesis in a pregnancy with a favorable outcome.Case reportA 37-year-old, gravida 4, para 0, woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XX, dup(9)(q22.3q34.1)[8]/46,XX[16]. Prenatal ultrasound findings were unremarkable. She was referred for genetic counseling, and repeat amniocentesis was performed at 21 weeks of gestation, which revealed a karyotype of 46,XX,dup(9)(q22.3q34.1)[7]/46,XX[25]. Simultaneous array comparative genomic hybridization (aCGH) on the DNA extracted from uncultured amniocytes revealed no genomic imbalance, or arr (1–22,X) × 2. Interphase fluorescence in situ hybridization (FISH) analysis on 105 uncultured amniocytes detected only one cell with the dup 9q signal with a mosaic dup 9q level of 1%, compared with 0% in normal control. At 37 weeks of gestation, a 2640-g female baby was delivered with no phenotypic abnormality. The cord blood had a karyotype of 46,XX,dup(9) (q22.3q34.1)[4]/46,XX[36], the umbilical cord had a karyotype of 46,XX,dup(9) (q22.3q34.1)[2]/46,XX[38], and the placenta had a karyotype of 46,XX. aCGH analysis on cord blood revealed no genomic imbalance. At age 2½ months, the baby was doing well, the peripheral blood of the baby had a karyotype of 46,XX,dup(9) (q22.3q34.1)[4]/46,XX[36], and interphase FISH analysis on buccal mucosal cells revealed no dup 9q signal in 100 buccal mucosal cells.ConclusionCytogenetic discrepancy may occur between cultured amniocytes and uncultured amniocytes in mosaic dup(9) (q22.3q34.1). Molecular cytogenetic analysis on uncultured amniocytes is useful for rapid distinguishing pseudomosaicism from true mosaicism under such a circumstance.     

Molecular cytogenetic characterization of de novo concomitant proximal 21q deletion of 21q11.2q21.3 and distal Xp deletion of Xp22.33p22.2 due to an unbalanced X;21 translocation detected by amniocentesis

ObjectiveWe present molecular cytogenetic characterization of de novo concomitant proximal 21q deletion of 21q11.2q21.3 and distal Xp deletion of Xp22.33p22.2 due to an unbalanced X; 21 translocation detected by amniocentesis.Case reportA 35-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 45,X,der(X)t(X; 21) (p22.2; q21.3),-21. Simultaneous array comparative genomic hybridization (aCGH) revealed the result of an 11.9-Mb Xp22.33p22.2 deletion encompassing HCCS, SHOX, AMELX and OFD1 and a 15.4-Mb 21q11.2q21.3 deletion encompassing NRIP1 and APP. The pregnancy was subsequently terminated, and a malformed fetus was delivered with craniofacial dysmorphism. The parental karyotypes were normal. Polymorphic DNA marker analysis by quantitative fluorescence polymerase chain reaction (QF-PCR) confirmed a paternal origin of the 21q proximal deletion. Cytogenetic analysis of cord blood confirmed the karyotype of 45,X,der(X)t(X; 21) (p22.2; q21.3),-21. aCGH analysis of the cord blood confirmed the prenatal diagnosis.ConclusionQF-PCR analysis is useful for determination of the parental origin of a de novo unbalanced X; autosome translocation detected by prenatal diagnosis. The information acquired is useful for genetic counseling under such a circumstance.     

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from ring chromosome 2

ObjectiveTo present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome (sSMC) derived from ring chromosome 2 [r(2)].Methods and ResultsA 35-year-old woman underwent amniocentesis at 17 weeks of gestation, because of advanced maternal age. Amniocentesis revealed a de novo ring-shaped sSMC in 11 of 23 colonies of cultured amniocytes. Repeated amniocenteses were made. The sSMC was characterized by array comparative genomic hybridization (aCGH), interphase fluorescence in situ hybridization (FISH) and quantitative fluorescent polymerase chain reaction (QF-PCR) on uncultured amniocytes. In uncultured amniocytes, aCGH showed a 39.49-Mb genomic gain in chromosome 2 encompassing 2q11.2→q21.2, interphase FISH revealed a mosaic level of 52% (52/100 cells), and QF-PCR manifested a diallelic pattern for chromosome 2, with gene dosage increase in the paternal allele of proximal 2q-specific DNA markers. In cultured amniocytes, the sSMC was characterized by metaphase FISH, spectral karyotyping (SKY) and multicolor banding (MCB) to contain the centromere and proximal 2q, and the karyotype was 47,XX,+r(2)(p11.1q21.2)[14]/46,XX[11]. The pregnancy was terminated. The fetus postnatally manifested facial dysmorphisms. Postnatal cytogenetic analyses revealed the karyotypes of 47,XX,+r(2)[12]/46,XX[28] in cord blood, 47,XX,+r(2)[7]/46,XX[33] in umbilical cord, 47,XX,+r(2)[13]/47,XX,+idic r(2)[3]/46,XX[24] in placenta and 47,XX,+r(2)[8]/47,XX,+idic r(2)[1]/46,XX[31] in amnion.ConclusionMolecular cytogenetic techniques such as aCGH, interphase FISH and QF-PCR on uncultured amniocytes, and SKY, MCB and metaphase FISH on cultured amniocytes are useful for characterization of the nature of a prenatally detected sSMC.     

Low-level mosaic trisomy 21 at amniocentesis in a pregnancy associated with a negative NIPT result,cytogenetic discrepancy in various tissues,perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome

ObjectiveWe present low-level mosaic trisomy 21 at amniocentesis associated with a favorable fetal outcome.Case reportA 31-year-old primigravid woman underwent non-invasive prenatal testing (NIPT) at 12 weeks of gestation, and the result was normal. She underwent amniocentesis at 16 weeks of gestation because of fetal choroid plexus cyst, and the result was 47,XX,+21[5]/46,XX[32]. Repeat amniocentesis was performed at 19 weeks of gestation, and the result was 47,XX,+21[5]/46,XX[15]. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr (21) × 3 [0.10], consistent with 10% mosaicism for trisomy 21. Prenatal ultrasound findings were unremarkable. She was referred for genetic counseling at 22 weeks of gestation, and the third amniocentesis was performed at 25 weeks of gestation, and the result was 46,XX (20/20 colonies). The parental karyotypes were normal. Simultaneous quantitative fluorescence polymerase chain reaction (QF-PCR) analysis on the DNA extracted from uncultured amniocytes and parental bloods excluded uniparental disomy (UPD) 21. aCGH analysis on uncultured amniocytes revealed arr 21q11.2q22.3 × 2.1 (log₂ ratio = 0.1), consistent with 10–15% mosaicism for trisomy 21. Fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed 30% (30/100 cells) mosaicism for trisomy 21. The woman was advised to continue the pregnancy, and a phenotypically normal 2800-g female baby was delivered at 38 weeks of gestation. The karyotype of cord blood, umbilical cord and placenta were 47,XX,+21[1]/46,XX[39]. 47,XX,+21[4]/46,XX[36] and 46,XX (40/40 cells), respectively. When follow-up at age two months, the neonate was phenotypically normal. The peripheral blood had a karyotype of 47,XX,+21[1]/46,XX[39], and FISH analysis on buccal mucosal cells revealed 8.4% (7/83 cells) mosaicism for trisomy 21, compared with 0% in the normal control.ConclusionLow-level mosaic trisomy 21 at amniocentesis can be associated with a negative NIPT result, cytogenetic discrepancy in various tissues, perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome.     

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from ring chromosome 4

ObjectiveTo present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome (sSMC) derived from ring chromosome, or r(4) by spectral karyotyping (SKY), fluorescence in situ hybridization (FISH), and array comparative genomic hybridization (aCGH).Materials, Methods, and ResultsA 37-year-old, primigravid woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a de novo ring-shaped sSMC in 16 of 31 amniocyte colonies. The parental karyotypes were normal. Level II ultrasound findings were unremarkable. Repeated amniocentesis revealed a karyotype of 47,XX,+mar[17]/46,XX[19]. The sSMC was characterized by SKY and FISH, which showed a chromosome 4 origin of the sSMC. aCGH demonstrated a 21.7-Mb gain in the gene dosage encompassing the region of 4p12→q13.2. The sSMC was r(4)(p12q13.2). The fetal karyotype was 47,XX,+r(4)(p12q13.2)[17]/46,XX[19]. The pregnancy was subsequently terminated. The fetus postnatally manifested hypertelorism, epicanthic folds, a prominent nose, a triangular face, low-set ears, clinodactyly of the fingers, and small big toes. Postnatal cytogenetic analyses of fetal and extraembryonic tissues revealed the karyotypes of 47,XX,+r(4)[18]/46,XX[21] in cord blood, 47,XX,+r(4)[20]/48,XX,+r(4),+r(4)[1]/46,XX[9] in umbilical cord, 47,XX,+r(4)[14]/47,XX,+dic r(4)[1]/46,XX[25] in skin, 47,XX,+r(4)[15]/46,XX[25] in amnion, and 47,XX,+r(4)[12]/47,XX,+dic r(4)[1]/46,XX[2] in placenta.ConclusionSKY, FISH, and aCGH are helpful in genetic counseling of prenatally detected sSMCs by providing the immediate and thorough information on the origin and genetic component of the sSMC.     

Prenatal diagnosis and molecular cytogenetic characterization of a de novo duplication of 2q12.2→q13 encompassing MALL,NPHP1, RGPD6 and BUB1

ObjectiveWe present prenatal diagnosis and molecular cytogenetic characterization of a de novo duplication of 2q12.2→q13 encompassing MALL, NPHP1, RGPD6 and BUB1.Case reportA 36-year-old, primigravid woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XX,dup(2) (q12.2q13). Simultaneous array comparative genomic hybridization (aCGH) analysis revealed a 6.1-Mb 2q12.2q13 duplication. aCGH analysis of the parental bloods did not find such a duplication. Prenatal ultrasound was unremarkable. After genetic counseling, the parents decided to terminate the pregnancy at 21 weeks of gestation, and a 420-g female fetus was delivered with no gross abnormalities. Postnatal cytogenetic analysis of the umbilical cord confirmed the prenatal diagnosis. The parental karyotypes were normal. aCGH analysis of the umbilical cord revealed the result of arr [GRCh37 (hg19)] 2q12.2q13 (107, 132, 950–113,065,779) × 3.0 with a 2q12.2→q13 duplication encompassing 20 OMIM genes including MALL, NPHP1, RGPD6 and BUB1. Polymorphic DNA marker analysis of quantitative fluorescence polymerase chain reaction (QF-PCR) on the DNAs extracted from the umbilical cord and parental bloods confirmed a maternal origin of the duplication of 2q12.2→q13.ConclusionAmniocentesis may incidentally detect a de novo chromosomal segmental duplication of maternal origin in the fetus. The genetic information acquired by molecular analyses such as aCGH and QF-PCR are useful for genetic counseling under such a circumstance.     

Mosaic trisomy 21 at amniocentesis associated with a favorable fetal outcome and perinatal progressive decrease of the trisomy 21 cell line

ObjectiveWe present mosaic trisomy 21 at amniocentesis associated with a favorable fetal outcome and perinatal progressive decrease of the trisomy 21 cell line.Case reportA 33-year-old woman underwent elective amniocentesis at 17 weeks of gestation because of anxiety, and the karyotype of cultured amniocytes was 47,XX,+21[4]/46,XX[13]. In 17 colonies of cultured amniocytes, four colonies had 47,XX,+21, while the other 13 colonies had 46,XX. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr (21) × 3 [0.32] consistent with 32% mosaicism for trisomy 21. Repeat amniocentesis performed at 25 weeks of gestation revealed 47,XX,+21[4]/46,XX[24] with four colonies of 47,XX,+21 and 24 colonies of 46, XX on cultured amniocytes, and arr 21q11.2q22.3 × 2.25 by aCGH, 19.2% mosaicism for trisomy 21 (20/104 cells) by interphase fluorescence in situ hybridization (FISH), and no uniparental disomy (UPD) 21 by quantitative fluorescence polymerase chain reaction (QF-PCR) on uncultured amniocytes. The parental karyotypes were normal, and prenatal ultrasound was unremarkable. A phenotypically normal 2815-g female baby was delivered at 38 weeks of gestation. Cytogenetic analysis on the cord blood, umbilical cord and placenta revealed the karyotype of 47,XX,+21[10]/46,XX[30]. 47,XX,+21[5]/46,XX[35] and 47,XX,+21[38]/46,XX[2], respectively. QF-PCR analysis on the DNA extracted from parental bloods, uncultured amniocytes, cord blood, umbilical cord and placenta confirmed a paternal origin of trisomy 21. When follow-up at age two months, the neonate was phenotypically normal, the peripheral blood had a karyotype of 47,XX,+21[6]/46,XX[34], and no trisomy 21 signals by interphase FISH was found on 100 buccal mucosal cells. When follow-up at age 13 months, the neonate was phenotypically normal, and the peripheral blood had a karyotype of 47,XX,+21[3]/46,XX[37].ConclusionMosaic trisomy 21 at amniocentesis can be a transient and benign condition, and the abnormal trisomy 21 cell line may decrease and disappear after birth.     

Prenatal diagnosis of a distal 3p deletion associated with fetoplacental chromosomal discrepancy and confined placental mosaicism detected by array comparative genomic hybridization

ObjectiveThis study is aimed at prenatal diagnosis of a distal 3p deletion associated with fetoplacental chromosomal discrepancy and confined placental mosaicism, and providing evidence for the limitation of array comparative genomic hybridization (aCGH) on placental tissues for molecular cytogenetic characterization of prenatally detected aneuploidy.Case ReportA 30-year-old woman underwent amniocentesis at 18 weeks of gestation because of maternal anxiety. Results of amniocentesis revealed a distal deletion of chromosome 3p. A malformed female fetus was delivered at 20 weeks of gestation with brachycephaly and facial dysmorphisms, and a cytogenetic analysis of the cord blood revealed a karyotype of 46,XX,del(3)(p26.1),inv(9)(p12q13). A whole-genome aCGH on uncultured cord blood and placental tissue was performed. The aCGH on cord blood revealed a 7.4-Mb deletion at 3p26.3-p26.1. However, the aCGH on placental tissue revealed a 32.42-Mb gene dosage increase at 3p26.1-p22.1 and a 26.28-Mb gene dosage increase at 1p36.33-p36.11 in addition to a 7.4-Mb deletion at 3p26.3-p26.1, indicating confined placental mosaicism for partial trisomy 3p (3p26.1→p22.1) and mosaicism for partial trisomy 1p (1p36.33→p36.11). The 7.4-Mb deleted region of 3p26.3-p26.1 contained the following genes: CHL1, CNTN4, CRBN, LRRN1, and ITPR1.ConclusionFetal tissue and amniocytes offer more reliable resources for aCGH characterization of prenatally detected aneuploidy compared with placental tissues. A molecular cytogenetic evaluation of prenatally detected aneuploidy using placental tissue should raise concerns of confined placental mosaicism and fetoplacental chromosomal discrepancy.     

Detection of de novo del(18)(q22.2) and a familial of 15q13.2-q13.3 microduplication in a fetus with congenital heart defects

ObjectiveWe present detection of de novo del(18)(q22.2) and a familial 15q13.2-q13.3 microduplication in a fetus with congenital heart defects (CHD).Case reportA 27-year-old, primigravid woman was referred for genetic counseling because of fetal CHD. Prenatal ultrasound at 17 weeks of gestation revealed pericardial effusion, cardiomegaly and a large ventricular septal defect. The pregnancy was subsequently terminated at 18 weeks of gestation, and a 192-g female fetus was delivered with facial dysmorphism. Cytogenetic analysis of the umbilical cord revealed a karyotype of 46,XX,del(18)(q22.2). The parental karyotypes were normal. Array comparative genomic hybridization (aCGH) of the placental tissue revealed a 2.08-Mb 15q13.2-q13.3 microduplication encompassing KLF13 and CHRNA7, and a 10.74-Mb 18q22.2-q23 deletion encompassing NFATC1. The phenotypically normal father carried the same 2.08-Mb 15q13.2-q13.3 microduplication. Polymorphic DNA marker analysis confirmed a paternal origin of the distal 18q deletion.ConclusionPrenatal diagnosis of CHD should include a complete genetic study of the embryonic tissues, and the acquired information is useful for genetic counseling.     

Inv dup del(10p): Prenatal diagnosis and molecular cytogenetic characterization

ObjectiveWe present molecular cytogenetic characterization of prenatally detected inverted duplication and deletion of 10p [inv dup del(10p)].Case reportA 39-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a derivative chromosome 10 with additional material at the end of the short arm of one chromosome 10. Simultaneous array comparative genomic hybridization (aCGH) analysis revealed the result of arr 10p15.3 (136,361–451,013) × 1, 10p15.3p12.1 (536,704–25,396,900) × 3 [GRCh37 (hg19)] with a 0.31-Mb deletion of 10p15.3 encompassing ZMYND11 and DIP2C, and a 24.86-Mb duplication of 10p15.3p12.1. The pregnancy was subsequently terminated, and a female fetus was delivered with facial dysmorphism. Postnatal aCGH analysis showed that the umbilical cord had the same result as that of amniotic fluid, whereas the placenta had only the deletion of 10p15.3. Fluorescence in situ hybridization (FISH) analysis of the cord blood confirmed inverted duplication and deletion of 10p. The cord blood had a karyotype of 46,XX,der(10) del(10) (p15.3)dup(10) (p15.3p12.1)dn. Polymorphic DNA marker analysis confirmed a maternal origin of the chromosome 10 aberration.ConclusionPrenatal diagnosis of inv dup del(10p) with haploinsufficiency of ZMYND11 should include a genetic counseling of mental retardation and chromosome 10p15.3 microdeletion syndrome. aCGH, FISH and polymorphic DNA marker analysis are useful for perinatal investigation of inv dup del(10p).     

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from chromosome 3

ObjectiveWe present prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome (sSMC) derived from chromosome 3.Case reportA 36-year-old woman underwent amniocentesis at 19 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+mar[6]/46,XX[18]. The mother's karyotype was 47,XX,+mar[4]/46,XX[46]. The father's karyotype was 46.XY. Array comparative genomic hybridization (aCGH) analysis of uncultured amniocytes revealed a result of arr 3q11.1q12.1 (93,575,285–98,956,687) × 2–3 [GRCh37 (hg19)]. Prenatal ultrasound findings were unremarkable. The parents elected to continue the pregnancy, and a 2470-g female baby was delivered at 37 weeks of gestation without phenotypic abnormalities. The cord blood had a karyotype of 47,XX,+mar[8]/46,XX[32]. aCGH analysis of cord blood revealed a result of arr 3q11.1q11.2 (93,649,973–97,137,764) × 2.4 [GRCh37 (hg19)] with a log2 ratio of 0.25 and a 30–40% mosaicism for 3.488-Mb dosage increase in 3q11.1-q11.2 encompassing four [Online Mendelian Inheritance in Man (OMIM)] genes of PROS1, ARL13B, NSUN3 and EPHA6. Metaphase fluorescence in situ hybridization (FISH) analysis confirmed 30% (6/20 cells) mosaicism for the sSMC(3) in the blood lymphocytes.ConclusionaCGH and FISH analyses are useful for perinatal investigation of a prenatally detected sSMC.     

Prenatal diagnosis of low-level mosaicism for trisomy 21 by amniocentesis in a pregnancy associated with maternal uniparental disomy of chromosome 21 in the fetus and a favorable outcome

ObjectiveWe present perinatal molecular cytogenetic analysis of low-level mosaicism for trisomy 21 in a pregnancy with maternal uniparental disomy (UPD) of chromosome 21 in the fetus.Case reportA 39-year-old woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+21[6]/46,XX[25]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed arr (21) × 2–3, (X) × 2 with about 18% gene dosage increase in chromosome 21 consistent with mosaic trisomy 21. Cordocentesis was performed at 20 weeks of gestation, and the cord blood lymphocytes had a karyotype of 47,XX,+21[3]/46,XX[72]. Prenatal ultrasound findings were unremarkable. After genetic counseling, the parents decided to continue the pregnancy. At 39 weeks of gestation, a 3,494-g phenotypically normal female baby was delivered without phenotypic features of Down syndrome. There was no dysplasia of middle phalanx of the fifth fingers of both hands. The cord blood had a karyotype of 47,XX,+21[2]/46,XX[48]. The placenta had a karyotype of 47,XX,+21[37]/46,XX[3]. The umbilical cord had a karyotype of 47,XX,+21[1]/46,XX[39]. aCGH analysis on the DNA extracted from cord blood revealed no genomic imbalance. Polymorphic DNA marker analysis on the DNAs extracted from cord blood and parental bloods revealed maternal uniparental heterodisomy 21 in the baby. Interphase fluorescence in situ hybridization analysis on buccal mucosal cells revealed trisomy 21 signals in 15/101 (14.9%) buccal cells at birth and in 1/122 (0.82%) buccal cells at age 45 days.ConclusionLow-level mosaicism for trisomy 21 at amniocentesis associated with maternal UPD 21 in the fetus can have a favorable outcome.     

Mosaic deletion-duplication syndrome of chromosome 3: prenatal molecular cytogenetic diagnosis using cultured and uncultured amniocytes and association with fetoplacental discrepancy

ObjectiveTo present prenatal molecular cytogenetic diagnosis of mosaicism for terminal 3p deletion and distal 3q duplication using cultured and uncultured amniocytes, and the association with fetoplacental discrepancy.Materials, Methods, and ResultsA 35-year-old primigravid woman was referred for genetic counseling at 21 weeks of gestation because of 20% (5/25 colonies) mosaicism for add(3)(p26) detected by amniocentesis. Repeated amniocenteses were performed. Array comparative genomic hybridization (aCGH) and interphase fluorescence in situ hybridization (FISH) were applied in the uncultured amniocytes. aCGH analysis detected 0.15-Mb microdeletion of 3p26.3 with CHL1 haploinsufficiency and a 49.42-Mb duplication of 3q24-q29 in the uncultured amniocytes. Interphase FISH analysis revealed 27.3% mosaicism (12/44 cells) in the uncultured amniocytes. Metaphase FISH analysis revealed 23.3% mosaicism (7/30 cells) in the cultured amniocytes. Conventional cytogenetic analysis showed a karyotype of 46,XX,der(3)(qter → q24::p26.3 → qter)[10]/46,XX[20] (33% mosaicism). Subsequent fetal blood sampling showed a karyotype of 46,XX,der(3) (qter → q24::p26.3 → qter)[5]/46,XX[35] (12.5% mosaicism). The parents elected to terminate the pregnancy, and a malformed fetus was delivered at 24 weeks of gestation with characteristic facial dysmorphism and clinodactyly of the hands. Cytogenetic analysis of the extraembryonic tissues revealed the results of 46,XX (40 cells) in placenta, 25% mosaicism (10/40 cells) in amniotic membrane and 50% mosaicism (20/40 cells) in umbilical cord.ConclusionOur presentation highlights the utility of molecular cytogenetic technologies in prenatal diagnosis of rare mosaic chromosome rearrangements and provides evidence for fetoplacental discrepancy under such circumstances.     

Prenatal diagnosis of maternal uniparental disomy 21 in association with low-level mosaic trisomy 21 at amniocentesis in a pregnancy associated with intrauterine growth restriction and a favorable outcome

ObjectiveWe present prenatal diagnosis of maternal uniparental disomy (UPD) 21 in association with low-level mosaic trisomy 21 at amniocentesis in a pregnancy associated with intrauterine growth restriction (IUGR) and a favorable outcome.Case reportA 42-year-old, gravida 2, para 0, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis initially revealed a karyotype of 46,XX in 20/20 colonies of cultured amniocytes. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed a result of arr [GRCh37] (21) × 3 [0.16], (X) × 2, compatible with mosaic trisomy 21. After extensive investigation, the final result of conventional cytogenetic analysis of cultured amniocytes was 47,XX,+21[1]/46,XX[40]. The parental karyotypes were normal. Repeat amniocentesis was performed at 21 weeks of gestation. The cultured amniocytes had a karyotype of 47,XX,+21[3]/46,XX[27] and the uncultured amniocytes had a mosaic trisomy 21 level of 8.8% (10/114 cells) by interphase fluorescence in situ hybridization (FISH), a mosaic trisomy 21 level of 10% (log₂ ratio = 0.08) by aCGH, and maternal UPD 21 by polymorphic DNA marker analysis. Prenatal ultrasound revealed IUGR. At 38 weeks of gestation, a phenotypically normal 2695-g baby was delivered. The cord blood and umbilical cord had the karyotype of 46,XX and maternal UPD 21. The placenta had a karyotype of 47,XX,+21[8]/46,XX[32] and a maternal origin of trisomy 21. Postnatal FISH analysis on 101 buccal mucosal cells showed 6.9% (7/101 cells) mosaicism compared with 2% (2/100 cells) in the normal control. The baby was doing well at age four months.ConclusionPregnancy with low-level mosaic trisomy 21 and maternal UPD 21 at amniocentesis can be associated with IUGR and a favorable outcome. Fetuses with maternal UPD 21 can be associated with mosaic trisomy 21 at amniocentesis.     

Prenatal diagnosis and molecular cytogenetic characterization of a 1.07-Mb microdeletion at 5q35.2–q35.3 associated with NSD1 haploinsufficiency and Sotos syndrome

ObjectiveTo present prenatal diagnosis and molecular cytogenetic characterization of a de novo 5q35 microdeletion associated with Sotos syndrome.MethodsThis was the first pregnancy of a 29-year-old woman. The pregnancy was uneventful until 27 weeks of gestation when left ventriculomegaly was first noted. At 31 weeks of gestation, polyhydramnios, macrocephaly, and ventriculomegaly were prominent on ultrasound, and left pyelectasis and bilateral ventriculomegaly were diagnosed on magnetic resonance imaging. The woman underwent amniocentesis and cordocentesis at 32 weeks of gestation. Conventional cytogenetic analysis was performed using cultured amniocytes and cord blood lymphocytes. Array comparative genomic hybridization (aCGH) was performed on uncultured amniocytes and parental blood. Metaphase fluorescence in situ hybridization (FISH) was performed on cultured lymphocytes.ResultsConventional cytogenetics revealed a karyotype of 46,XX. aCGH on uncultured amniocytes revealed a de novo 1.07-Mb microdeletion at 5q35.2–q35.3 encompassing NSD1. Metaphase FISH analysis on the cord blood lymphocytes confirmed the deletion at 5q35.2. The postnatal phenotype was consistent with Sotos syndrome.ConclusionFetuses with Sotos syndrome may present macrocephaly, polyhydramnios, ventriculomegaly, and pyelectasis in the third trimester. aCGH and metaphase FISH are useful for rapid diagnosis of 5q35 microdeletion associated with Sotos syndrome.     

Prenatal diagnosis and molecular cytogenetic characterization of chromosome 22q11.2 deletion syndrome associated with congenital heart defects

ObjectiveTo report prenatal diagnosis of 22q11.2 deletion syndrome in a pregnancy with congenital heart defects in the fetus.Case reportA 26-year-old, primigravid woman was referred for counseling at 24 weeks of gestation because of abnormal ultrasound findings of fetal congenital heart defects. The Level II ultrasound revealed a singleton fetus with heart defects including overriding aorta, small pulmonary artery, and ventricular septal defect. Cordocentesis was performed. The DNA extracted from the cord blood was analyzed by multiplex ligation-dependent amplification (MLPA). The MLPA showed deletion in the DiGeorge syndrome (DGS) critical region of chromosome 22 low copy number repeat (LCR) 22-A∼C. Conventional cytogenetic analysis revealed a normal male karyotype. Repeated amniocentesis and cordocentesis were performed. Whole-genome array comparative genomic hybridization (aCGH) on cord blood was performed. aCGH detected a 3.07-Mb deletion at 22q11.21. Conventional cytogenetic analysis of cultured amniocytes revealed a karyotype 46,XY. Metaphase fluorescence in situ hybridization (FISH) analysis on cultured amniocytes confirmed an interstitial 22q11.2 deletion.ConclusionPrenatal ultrasound findings of congenital heart defects indicate that the fetuses are at increased risk for chromosome abnormalities. Studies for 22q11.2 deletion syndrome should be considered adjunct to conventional karyotyping. Although FISH has become a standard procedure for diagnosis of 22q11.2 deletion syndrome, MLPA can potentially diagnose a broader spectrum of abnormalities, and aCGH analysis has the advantage of refining the 22q11.2 deletion breakpoints and detecting uncharacterized chromosome rearrangements or genomic imbalances.     

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

ObjectiveWe 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 reportA 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.ConclusionMosaic 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.     

Wolf–Hirschhorn syndrome: Prenatal diagnosis and molecular cytogenetic characterization of a de novo distal deletion of 4p (4p16.1 → pter) in a fetus with facial cleft and preaxial polydactyly

ObjectiveWe present prenatal diagnosis and molecular cytogenetic characterization of Wolf–Hirschhorn syndrome (WHS) in a fetus with facial cleft and preaxial polydactyly.Materials and methodsA 37-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age, and the result showed an aberrant chromosome 4 or 46,XX,add(4) (p15.3). The woman consulted our clinics at 22 weeks of gestation and requested for repeat amniocentesis. Prenatal ultrasound revealed intrauterine growth restriction, facial cleft, vermian hypoplasia of cerebellum, micrognathia and absent stomach. Conventional cytogenetic analysis was performed on cultured amniocytes, parental bloods and cord blood. Array comparative genomic hybridization (aCGH) and quantitative fluorescent polymerase chain reaction (QF-PCR) were performed on the DNAs extracted from uncultured amniocytes and parental bloods. Fluorescence in situ hybridization (FISH) analysis was performed on cultured metaphase amniocytes.ResultsaCGH analysis on uncultured amniocytes revealed arr 4p16.3p16.1 (74,447–8,732,731) × 1.0 [GRCh37 (hg19)] with an 8.66-Mb deletion of 4p16.3-p16.1 encompassing 70 [Online Mendelian Inheritance of in Man (OMIM)] genes including ZNF141, FGFRL1, TACC3, LETM1, NSD2 and NELFA. QF-PCR revealed a paternal origin of the distal 4p deletion. Conventional cytogenetic analysis revealed 46,XX,del(4) (p16.1)dn in the fetus. Metaphase FISH analysis confirmed a 4p16 deletion. The parental karyotypes were normal. The pregnancy was subsequently terminated, and a malformed fetus was delivered with typical WHS facial dysmorphism, bilateral cleft lip and palate, and preaxial polydactyly on the right hand.ConclusionaCGH, QF-PCR and FISH help to delineate the nature of a prenatally defected aberrant chromosome, and the acquired information is useful for genetic counseling.