Prenatal diagnosis and molecular cytogenetic characterization of low-level mosaicism for tetrasomy 18p at amniocentesis in a pregnancy with a favorable outcome

Mosaic distal 10q deletion or 46,XY,del(10) (q26.13)/46,XY at amniocentesis and cordocentesis in a pregnancy associated with cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes, perinatal progressive decrease of the aneuploid cell line and a favorable fetal outcome

OBJECTIVE

We present mosaic distal 10q deletion at prenatal diagnosis in a pregnancy associated with a favorable fetal outcome.

CASE REPORT

A 40-year-old, gravida 2, para 0, woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY, del(10) (q26.13)[6]/46,XY[17]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes showed 35% mosaicism for the 10q26.13q26.3 deletion. At 22 weeks of gestation, she underwent cordocentesis which revealed a karyotype of 46,XY,del(10) (q26.13)[16]/46,XY[24]. Prenatal ultrasound findings were normal. At 24 weeks of gestation, she was referred for genetic counseling, and repeat amniocentesis revealed a karyotype of 46,XY,del(10) (q26.13)[4]/46,XY[22]. The parental karyotypes were normal. Molecular genetic analysis on uncultured amniocytes revealed no uniparental disomy (UPD) 10 by quantitative fluorescence polymerase chain reaction (QF-PCR), arr 10q26.13q26.3 × 1.6 (40% mosaicism) by aCGH, and 29.8% (31/104 cells) mosaicism for the distal 10q deletion by interphase fluorescence in situ hybridization (FISH). The woman was advised to continue the pregnancy, and a phenotypically normal 2,900-g male baby was delivered at 39 weeks of gestation. The cord blood had a karyotype of 46,XY,del(10) (q26.13)[6]/46,XY[34], and both the umbilical cord and the placenta had the karyotype of 46,XY. When follow-up at age four months, the neonate was normal in phenotype and development. The peripheral blood had a karyotype of 46,XY,del(10) (q26.13)[5]/46,XY[35], and interphase FISH analysis on buccal mucosal cells showed 8% (8/102 cells) mosaicism for distal 10q deletion.

CONCLUSION

Mosaic distal 10q deletion with a normal cell line at prenatal diagnosis can be associated with a favorable fetal outcome and perinatal progressive decrease of the aneuploid cell line.

Mosaicism for a 12p12.1p12.2 microdeletion with a normal euploid cell line at amniocentesis in a pregnancy with a favorable outcome and postnatal decrease of the aneuploid cell line with microdeletion

OBJECTIVE

We present mosaicism for a 12p12.1p12.2 microdeletion with a normal euploid cell line at amniocentesis in a pregnancy with a favorable outcome and postnatal decrease of the aneuploid cell line with microdeletion.

CASE REPORT

A 35-year-old woman, gravida 2, para 1, underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed mosaic 46,XY,del (12) (p11.2p12), and array comparative genomic hybridization (aCGH) revealed arr Xp22.31 × 2 mat, 12p12.2p12.1 × 1 [0.36]dn with a 4.15-Mb 36% mosaicism for a 12p12.1p12.2 microdeletion. At 22 weeks of gestation, she underwent cord blood sampling of which aCGH revealed arr Xp22.31 × 2 mat, 12p12.2p12.1 × 1 [0.34]dn with a 4.24-Mb 34% mosaicism for a 12p12.1p12.2 microdeletion. Prenatal ultrasound findings were unremarkable. She was referred for genetic counseling, and continuing pregnancy was advised. A 2990-g male baby was delivered at 38 weeks of gestation with no phenotypic abnormality. When follow-up at age 1½ months, the neonate was phenotypically normal. The karyotype of peripheral blood was 46,XY. aCGH analysis on the DNA extracted from peripheral blood revealed the result of arr 12p12.1p12.2 (20, 367, 240-24,489,386) × 1.87, arr Xp22.31 (6,488,721-8,097,511) × 2.0 [GRCh37 (hg19)] with 10-15% (log2 ratio = 0.1) mosaicism for a 4.122-Mb 12p12.1-p12.2 microdeletion encompassing 17 OMIM genes of PDE3A, SLCO1C1, SLCO1B3, SLCO1B1, IAPP, PYROXD1, RECQL, GOLT1B, SPX, GYS2, LDHB, KCNJ8, ABCCP, CMAS, C2CD5, ETNK1 and SOX5 and a 1.609-Mb Xp22.31 duplication encompassing two OMIM genes of STS and VCX. Interphase fluorescence in situ hybridization (FISH) analysis on 104 buccal mucosal cells using 12p12.1-specific probe showed 17% (18/104 cells) mosaicism for a 12p12.1 deletion. Polymorphic DNA marker analysis on the DNA extracted from proband's blood and parental bloods determined a paternal origin of the mosaic 12p12.1 deletion.

CONCLUSION

Mosaicism for a 12p12.1p12.2 microdeletion at amniocentesis with a normal euploid cell line can be a benign condition in association with a favorable fetal outcome and postnatal decrease of the aneuploid cell line with microdeletion.

Mosaicism for a 15q11.2 microduplication with a normal euploid cell line at amniocentesis in a pregnancy with a favorable fetal outcome and postnatal decrease of the aneuploid cell line with the microduplication

OBJECTIVE

We present mosaicism for a 15q11.2 microduplication with a normal euploid cell line at amniocentesis in a pregnancy with a favorable fetal outcome and postnatal decrease of the aneuploid cell line with the microduplication.

CASE REPORT

A 35-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed 33.76% mosaicism for a 15q11.2 microduplication. She was referred for genetic counseling. Repeat amniocentesis was performed at 23 weeks of gestation, and the karyotype was 46,XY. Simultaneous aCGH analysis on the DNA extracted from uncultured amniocytes revealed the result of arr [GRCh37 (hg19)] 15q11.2 (23, 889, 686-25,514,125) × 2.45, consistent with a mosaic 1.624-Mb microduplication with the mosaic level of 40%-45% (log₂ ratio = 0.28) encompassing nine OMIM genes of MAGEL2, NDN, PWRN2, PWRN1, NPAP1, SNRPN, SNHG14, SNORD116-1 and SNORD115-1. Interphase fluorescence in situ hybridization (FISH) analysis on 100 uncultured amniocytes detected a 15q11.2 duplication in 19 cells, consistent with 19% (19/100 cells) mosaic15q11.2 duplication. Polymorphic DNA marker analysis excluded uniparental disomy (UPD) 15. Prenatal ultrasound findings were unremarkable. She was advised to continue the pregnancy, and a 3865-g phenotypically normal male baby was delivered. aCGH analysis on the DNA extracted from cord blood at birth and buccal mucosal cells at age four months revealed arr (1-22) × 2, X × 1, Y × 1 and detected no genomic imbalance in all samples. Interphase FISH analysis on 104 buccal mucosal cells at age four months detected four cells (4/104 = 4%) with a 15q11.2 duplication, compared with 0% (0/102 cells) in the normal control. The neonate was normal in the development.

CONCLUSION

Mosaicism for a 15q11.2 microduplication at amniocentesis with a normal euploid cell line can be a benign condition and associated with a favorable fetal outcome and postnatal decrease of the aneuploid cell line with the microduplication.

Mosaic 46,XY,dup(14) (q12q22.3)/46, XY at amniocentesis in a pregnancy associated with a favorable fetal outcome and cytogenetic discrepancy in various tissues

OBJECTIVE

We present mosaic 46,XY,dup (14) (q12q22.3)/46, XY at amniocentesis in a pregnancy associated with a favorable fetal outcome and cytogenetic discrepancy in various tissues.

CASE REPORT

A 41-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. This pregnancy was conceived by in vitro fertilization and embryo transfer. Cytogenetic analysis on cultured amniocytes revealed a karyotype of 46,XY, dup (14) (q12q22.3)[7]/46,XY [13], and simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed arr 14q12q22.3 × 2-3 with 25% mosaicism for partial 14q duplication. She was referred for genetic counseling. Prenatal ultrasound and parental karyotypes were normal. Repeat amniocentesis at 22 weeks of gestation revealed a karyotype of 46,XY,dup (14) (q12q22.3)[6]/46,XY [14], and in uncultured amniocytes, quantitative fluorescence polymerase chain reaction (QF-PCR) analysis excluded uniparental disomy (UPD) 14, aCGH revealed arr 14q12q22.3 × 2.3 with 30% mosaicism for dup (14) (q12q22.3), and interphase fluorescence in situ hybridization (FISH) showed 19.4% (24/124 cells) mosaicism for partial 14q duplication. She was encouraged to continue the pregnancy, and a 2450-g phenotypically normal male baby was delivered at 40 weeks of gestation. The karyotypes of cord blood, umbilical cord and placenta were 46,XY,dup (14) (q12q22.3)[14]/46,XY [26], 46,XY,dup (14) (q12q22.3)[7]/46,XY [33] and 46,XY,dup (14) (q12q22.3)[3]/46,XY [37], respectively. When follow-up at age four months, the neonate was phenotypically normal. The karyotype of peripheral blood was 46,XY,dup (14) (q12q22.3)[27]/46,XY [13], and interphase FISH analysis on 105 buccal mucosal cells detected partial 14q duplication signals in 5 cells (4.8% mosaicism). When follow-up at age nine months, the neonate was phenotypically normal. The karyotype of peripheral blood was 46,XY,dup (14) (q12q22.3)[25]/46,XY [15].

CONCLUSION

Mosaic dup (14) (q12q22.3) with a normal cell line at amniocentesis may be a benign condition, and can be associated with a favorable fetal outcome and cytogenetic discrepancy in various tissues.

Mosaic 46,XY,der(15)t(6;15)(q25.1;p12)/46,XY at amniocentesis in a pregnancy associated with a favorable fetal outcome and postnatal decrease of the aneuploid cell line with the unbalanced translocation

OBJECTIVE

We present mosaic 46,XY,der(15)t(6;15)(q25.1;p12)/46,XY at amniocentesis in a pregnancy associated with a favorable fetal outcome and postnatal decrease of the aneuploid cell line with the unbalanced translocation.

CASE REPORT

A 34-year-old primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY,add(15)(p12)[17]/46,XY[5]. A second amniocentesis at 19 weeks of gestation revealed a karyotype of 46,XY,der(15)t(6;15)(q25.1;p12)[12]/46,XY[8], and array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed arr arr 6q25.1q27×2-3 with 40% mosaic level. She was referred for genetic counseling. Prenatal ultrasound and the parental karyotypes were normal. A third amniocentesis at 24 weeks of gestation revealed a karyotype of 46,XY,der(15)t(6;15)(q25.1;p12)[23]/46,XY[1], and in uncultured amniocytes, aCGH analysis revealed arr 6q25.1q27×2.5, interphase fluorescence in situ hybridization (FISH) revealed 51% mosaicism (51/100 cells) for partial trisomy 6q and quantitative fluorescence polymerase chain reaction (QF-PCR) analysis determined maternal origin of the aberrant chromosome and excluded uniparental disomy (UPD) 15 and UPD 6. A fourth amniocentesis at 27 weeks of gestation revealed a karyotype of 46,XY,der(15)t(6;15)(q25.1;p12)[21]/46,XY[5], and in uncultured amniocytes, aCGH analysis revealed arr 6q25.1q27×2.46, and interphase FISH revealed 35% mosaicism (35/100 cells) for partial trisomy 6q. At 39 weeks of gestation, a healthy 3028-g male baby was delivered without any phenotypic abnormality. The karyotypes of cord blood, umbilical cord and placenta were 46,XY,der(15)t(6;15)(q25.1;p12)[2]/46,XY,der(15)t(6;15)(q25.1;p12)[29]/46,XY[11] and 46,XY, respectively. When follow-up at age one month, the neonate was phenotypically normal, the peripheral blood had a karyotype of 46,XY (40/40 cells), and FISH analysis on 105 buccal mucosal cells detected five cells with partial trisomy 6q compared with 2% mosaicism (2/100 cells) in the normal control.

CONCLUSION

Mosaicism for an unbalanced translocation with a normal cell line without UPD at amniocentesis can be a transient and benign condition, and can be associated with a favorable fetal outcome and postnatal decrease of the aneuploid cell line.

Mosaic tetrasomy 9p at amniocentesis in a pregnancy associated with a favorable fetal outcome, perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy in various tissues

OBJECTIVE

We present mosaic tetrasomy 9p at amniocentesis in a pregnancy associated with a favorable fetal outcome, perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy in various tissue.

CASE REPORT

A 33-year-old primigravid woman underwent elective amniocentesis at 18 weeks of gestation because of anxiety, and the karyotype of cultured amniocytes was 47,XX,+i (9) (p10)[20]/46,XX [55]. Cordocentesis was performed at 20 weeks of gestation, and the karyotype of cord blood was 47,XX,+i (9) (p10)[7]/46,XX [15]. She was referred for genetic counseling at 23 weeks of gestation, and repeat amniocentesis revealed a karyotype of 47,XX,+i (9) (p10)[1]/46,XX [16] with seven cells in one colony having tetrasomy 9p in cultured amniocytes, and in uncultured amniocytes, quantitative fluorescence polymerase chain reaction (QF-PCR) analysis excluded uniparental disomy (UPD) 9 and determined paternal origin of the extra i (9p), array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed arr 9p24.3p13.1 × 3.0 consistent with 50% mosaicism for tetrasomy 9p, and interphase fluorescence in situ hybridization (FISH) on uncultured amniocytes showed 22.6% (12/53 cells) mosaicism for tetrasomy 9p. A third amniocentesis at 27 weeks of gestation revealed a karyotype of 46, XX (10/10 colonies) in cultured amniocytes, and interphase FISH analysis on uncultured amniocytes revealed 20% (20/100 cells) mosaicism for tetrasomy 9p. The parental karyotypes and prenatal ultrasound were normal. At 39 weeks of gestation, a phenotypically normal 3388-g female baby was delivered. The karyotypes of cord blood, umbilical cord and placenta were 47,XX,+idic (9) (q12)[19]/46,XX [21] or 47,XX,+idic (9) (pter→q12:q12→pter)[19]/46,XX [21], 47,XX,+idic (9) (q12)[1]/46,XX [39] and 47,XX,+idic (9) (q12)[4]/46,XX [36], respectively. When follow-up at age two months, the neonate was phenotypically normal, the peripheral blood had a karyotype of 47,XX,+idic (9) (q12)[18]/46,XX [22], and interphase FISH analysis on 100 buccal mucosal cells revealed 1% (1/100 cells) mosaicism for tetrasomy 9p. When follow-up at age seven months, the neonate was phenotypically normal, and the peripheral blood had a karyotype of 47,XX,+idic(9)(q12)[14]/46,XX[26].

CONCLUSION

Mosaic tetrasomy 9p at amniocentesis can be a transient and benign condition, and can be associated with a favorable fetal outcome and perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy in various tissue.

A Rare and Unusual Case of Trisomy 10p with Terminal 14q Deletion: A Multidisciplinary Approach

Trisomy 10p is a rare entity to be diagnosed and so is terminal 14q deletion. The total number of trisomy 10p cases reported to date is estimated to be in double digits. The number of terminal 14q deletion cases that have been reported in the literature is even lesser than that of trisomy 10p. Simultaneous occurrence of these genetic aberrations is, therefore, extremely rare. Herein, we document a case of a 14-month-old female diagnosed with trisomy 10p and terminal 14q deletion, who presented with an inability to sit without support and had difficulty in holding her neck. She had no means of independent indoor mobility, which was further limiting her development by exploration. Clinical features included hypotonia, developmental delay, extraneous movements of the head and tongue, intellectual impairment, and facial dysmorphism. She could maintain tripod sitting for less than a minute. Physiotherapy intervention was based on principles of neurodevelopmental treatment and sensory integration. After nine months of physiotherapy intervention, her total gross motor function measure (GMFM) score improved from 11% to 40%. The functional gains were maintained with a home exercise program, after almost one year of discontinuation of institution-based physiotherapy. To the best of our knowledge, this is the first report on the management of a child with the diagnosis of trisomy 10p along with terminal 14q deletion. Further research on the role of early intervention to maximize functional potential in rare genetic conditions is warranted.

Variable degree of mosaicism for tetrasomy 18p in phenotypically discordant monozygotic twins-Diagnostic implications

Background

Phenotypically discordant monozygotic twins (PDMZTs) offer a unique opportunity to study post‐zygotic genetic variation and provide insights into the linkage between genotype and phenotype. We report a comprehensive analysis of a pair of PDMZTs.

Methods

Dysmorphic features and delayed neuro‐motor development were observed in the proband, whereas her twin sister was phenotypically normal. Four tissues (blood, skin, hair follicles, and buccal mucosa) from both twins were studied using four complementary methods, including whole‐exome sequencing, karyotyping, array CGH, and SNP array.

Results

In the proband, tetrasomy 18p affecting all studied tissues except for blood was identified. Karyotyping of fibroblasts revealed isochromosome 18p [i(18p)] in all metaphases. The corresponding analysis of the phenotypically normal sister surprisingly revealed low‐level mosaicism (5.4%) for i(18p) in fibroblasts.

Conclusion

We emphasize that when mosaicism is suspected, multiple tissues should be studied and we highlight the usefulness of non‐invasive sampling of hair follicles and buccal mucosa as a convenient source of non‐mesoderm‐derived DNA, which complements the analysis of mesoderm using blood. Moreover, low‐level mosaic tetrasomy 18p is well tolerated and such low‐level mosaicism, readily detected by karyotyping, can be missed by other methods. Finally, mosaicism for low‐level tetrasomy 18p might be more common in the general population than it is currently recognized, due to detection limitations.