"It becomes your whole life"-Exploring experiences of reciprocal translocation carriers and their partners.

Reciprocal translocation carriers are often diagnosed when they are experiencing difficulties conceiving or after a pregnancy affected by an unbalanced set of chromosomes inherited from the balanced carrier parent. Having a reciprocal translocation is not uncommon; carriers can benefit from reproductive options to achieve a healthy, chromosomally balanced, pregnancy. The aim of this study was to explore the lived experience of carriers and their partners. We conducted 13 semi-structured telephone interviews. Participants were recruited through Victorian Clinical Genetics Services and interviews took place between May and September 2020. Interview transcripts were analyzed using thematic analysis. Reciprocal translocation carriers and their partners described long term emotional and reproductive impacts, with carrier status identified at the time of prenatal diagnosis having marked emotional consequences. Couples facing reproductive challenges found the diagnosis created uncertainty for their future. When considering a pregnancy, couples worried about experiencing a miscarriage; during pregnancy, there was a reluctance to have an invasive diagnostic procedure due to fearing the risk of losing an unaffected pregnancy. Adaptation to their new reality involved having access to accurate information, peer support and maintaining hope. Couples valued having the option to know the carrier status of their children. The complex impacts of carrying a reciprocal translocation highlight the importance of access to specialist genetic counseling services to ensure couples are supported in understanding the implications of their translocation.

Unbalanced translocation der(5;17) resulting in a TP53 loss as recurrent aberration in myelodysplastic syndrome and acute myeloid leukemia with complex karyotype.

A complex karyotype, detected in myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML), is associated with a reduced median survival. The most frequent chromosomal aberrations in complex karyotypes are deletions of 5q and 17p harboring the tumor suppressor gene TP53. The unbalanced translocation der(5;17) involving chromosome 5q and 17p is a recurrent aberration in MDS/AML, resulting in TP53 loss. We analyzed the karyotypes of 178 patients with an unbalanced translocation der(5;17) using fluorescence R-/G-banding analysis. Whenever possible, fluorescence in situ hybridization (FISH) (n = 138/141), multicolor FISH (n = 8), telomere length measurement (n = 9), targeted DNA sequencing (n = 13), array-CGH (n = 7) and targeted RNA sequencing (n = 2) were conducted. The der(5;17) aberration was accompanied with loss of genetic material in 7q (53%), -7 (27%), gain of 21q (29%), +8 (17%) and - 18 (16%) and all analyzed patients (n = 13) showed a (likely) pathogenic variant inTP53. The der(5;17) cohort showed significantly shortened telomeres in comparison to the healthy age-matched controls (P < .05), but there was no significant telomere shortening in comparison to MDS/AML patients with a complex karyotype without der(5;17). No fusion genes resulted from the unbalanced translocation. This study demonstrates that the unbalanced translocation der(5;17) is associated with a biallelic inactivation of TP53 due to a deletion of TP53 in one allele and a pathogenic variant of the second TP53 allele. Since the breakpoints are located within (near-) heterochromatic regions, alterations of DNA methylation or histone modifications may be involved in the generation of der(5;17).

Recurrence of an early postzygotic rescue of an inherited unbalanced translocation resulting in mosaic segmental uniparental isodisomy of chromosome 11q in siblings.

Balanced translocations are associated with a risk of transmission of unbalanced chromosomal rearrangements in the offspring. Such inherited chromosomal abnormalities are typically non-mosaic as they are present in the germline. We report the recurrence in two siblings of a mosaicism for a chromosomal rearrangement inherited from their asymptomatic father who carried a balanced t(2;11)(q35;q25) translocation. Both siblings exhibited a similar phenotype including intellectual disability, dysmorphic features, kyphoscoliosis, and cervical spinal stenosis. Karyotyping, fluorescence in situ hybridization and SNP array analysis of blood lymphocytes of both siblings identified two cell lines: one carrying a 2q35q37.3 duplication and a 11q25qter deletion (~90% cells), and one carrying an 11q uniparental isodisomy of maternal origin (~10% cells). We hypothesize that these mosaics were related to a postzygotic rescue mechanism which unexpectedly recurred in both siblings.

A phenotypically diverse family with an atypical 22q11.2 deletion due to an unbalanced 18q23;22q11.2 translocation.

The 22q11.2 deletion syndrome (22q11.2 DS) is the most common deletion syndrome in humans. In most cases, it occurs de novo. A rare family of three with 22q11.2 deletion syndrome (22q11.2 DS) resulting from an unbalanced 18q;22q translocation is reported here. Their deletion region is atypical in that it includes only 26 of the 36 genes in the minimal critical 22q11.2 DS region but it involves the loss of the centromeric 22q region and the entire p arm. The deletion region overlaps with seven other rare atypical cases; common to all cases was the loss of a region including SEPT5-GP1BB proximally and most of ARVCF distally. Interrogation of the deleted 22q region proximal to the canonical 22q11.2 deletion region in the DECIPHER database showed seven cases with isolated or combined traits of 22q11.2 DS, including three with clefts. The phenotypes in the present family thus may result from the loss of a subset of genes in the critical region, or alternatively the loss of other genes or sequences in the proximal 22q deletion region, or interactive effects among these. Despite the identical deletion locus in the three affected family members, expression of the 22q11.2 DS traits differed substantially among them. These three related cases thus contribute to knowledge of 22q11.2 DS in that their unusual deletion locus co-occurred with the cardinal features of the syndrome while their identical deletions are associated with variable phenotypic expression.

Non-invasive prenatal diagnosis for translocation carriers-YES please or NO go?

INTRODUCTION: The presence of an unbalanced familial translocation can be reliably assessed in the cytotrophoblast of chorionic villi. However, carriers of a balanced translocation often decline invasive testing. This study aimed to investigate whether an unbalanced translocation can also be diagnosed in cell free DNA by whole-genome non-invasive prenatal screening (NIPS). MATERIAL AND METHODS: Pregnant women carrying a fetus with an unbalanced familial translocation, for whom NIPS as well as microarray data were available, were included in this retrospective assessment. NIPS was performed in the course of the TRIDENT study. RESULTS: In 12 cases, both NIPS and microarray data were available. In 10 of 12 cases the unbalanced translocation was correctly identified by NIPS without prior knowledge on parental translocation. One was missed because the fetal fraction was too low. One was missed because of technical restrictions in calling 16p gains. CONCLUSIONS: This study supports the hypothesis that routine NIPS may be used for prenatal diagnosis of unbalanced inheritance of familial translocations, especially with prior knowledge of the translocation allowing focused examination of the involved chromosomal regions. Our study showed that routine shallow sequencing designed for aneuploidy detection in cell free DNA may be sufficient for higher resolution NIPS, if specialized copy number software is used and if sufficient fetal fraction is present.

Unbalanced X;9 translocation in an infertile male with de novo duplication Xp22.31p22.33.

PURPOSE: Male carriers of an X-autosome translocation are generally infertile, regardless of the position of the breakpoint on the X chromosome while the pathogenicity of Xp22.3 subtelomeric duplications is under debate. To shed light into this controversy, we present a rare case, of an azoospermic male with no other significant clinical findings, in whom classical cytogenetics revealed additional unbalanced chromosomal material, at the telomere of the long arm of one homolog of chromosome 9. METHODS: In peripheral blood specimens of the index case and his parents, we performed GBanding, Inverted-DAPI Banding, AgNOR staining, Telomere specific Fluorescence in Situ Hybridization (FISH), Molecular karyotyping by Multi-color FISH, whole genome SNP microarrays, sub-telomeric MLPA, and transcription analysis of the expression of KAL1 gene by RT-PCR. RESULTS: Multi-color FISH revealed an unbalanced translocation involving the short arm of chromosome X. SNP microarray analysis combined to classical cytogenetics and MLPA demonstrated a de novo 8.796 Mb duplication of Xp22.31-p22.33. Compared to three control specimens, the patient presented significantly elevated expression levels of KAL1 mRNA in peripheral blood, suggesting transcriptional functionality of the duplicated segment. CONCLUSIONS: The duplicated segment contains the pseudo-autosomal region PAR1 and more than 30 genes including SHOX, ARSE, STS, KAL1, and FAM9A and is not listed as polymorphic. Our data advocate that duplications of the Xp22.3 region may not be associated with a clinical consequence.

Deletion 21pterq22.11: Report of a Patient with Dysmorphic Features, Hypertonia, and Café-au-Lait Macules and Review of the Literature.

Partial monosomy 21 results in a great variability of clinical features that may be associated with the size and location of the deletion. In this study, we report a 22-month-old girl who showed a 45,XX,add(12)(p13)dn,-21 karyotype. The final cytogenomic result was 45,XX,der(12)t(12;21)(p13;q22.11) dn,-21.arr[hg19] 21q11.2q22.11(14824453_33868129)×1 revealing a deletion from 21pter to 21q22.11. Clinical manifestation of the patient included hypertonia, a long philtrum, epicanthic folds, low-set ears, and café-au-lait macules - a phenotype considered as mild despite the relatively large size of the deletion compared to patients from the literature.

Novel Unbalanced Translocations Affecting the Long Arms of Chromosomes 10 and 22 Cause Complex Syndromes with Very Severe Neurodevelopmental Delay, Speech Impairment, Autistic Behavior, and Epilepsy.

Isolated abnormalities in terminal regions of chromosomes 10q and 22q were formerly described in patients affected by neuropsychological impairment, abnormal facies, and heterogeneous structural abnormalities of the body. Chromosomes 10q and 22q harbor important genes that play a major role in CNS development, like DOCK1 and SHANK3, and in overall body growth, like FGFR2 and HTRA1. By using clinical, neuroradiological, neurophysiological, and genetic assessment, we studied 3 siblings affected by 2 different forms of very severe neuropsychological impairment with structural physical abnormalities, epilepsy, and body overgrowth. The genetic analysis revealed 2 different unbalanced translocations t(10;22)(q26.13;q13.32) of genetic material between the long arms of chromosomes 10 and 22, deriving from a maternal balanced translocation. Consequences of the unbalanced translocation were the simultaneous partial monosomy of 10q26.13 to 10qter and partial trisomy of 22q13.32 to 22qter in 2 patients and the simultaneous trisomy distal q10 and monosomy distal q22 in 1 patient, respectively. To the best of our knowledge, we here describe for the first time a causal association between an unbalanced translocation t(10;22) affecting the long arms of both chromosomes 10 and 22 and a very severe neurodevelopmental delay in 3 siblings.

Oligo-based aCGH analysis reveals cryptic unbalanced der(6)t(X;6) in pediatric t(12;21)-positive acute lymphoblastic leukemia.

Secondary chromosomal aberrations are necessary for development of overt leukemia in t(12;21)/ETV6-RUNX1-positive acute lymphoblastic leukemia (ALL). Conventional cytogenetic analysis supplemented with locus-specific FISH analyses is gold standard to detect important clonal aberrations in this disease group. However, adequate chromosome banding analysis may often be hampered by poor chromosome morphology and banding patterns in pediatric ALL cases, which may hinder identification of possible clinical important additional chromosomal aberrations. We used oligo-based high-resolution aCGH (oaCGH) analysis as an adjunct tool to enhance conventional cytogenetic analysis in pediatric acute B-cell lymphoblastic leukemia in a prospective single center study during a 4-year period (2012-2015). In a consecutive series of 45 pediatric B-ALLs, we identified eight patients with t(12;21)/ETV6-RUNX1 fusion by FISH analysis. In three of the patients, oaCGH analysis revealed concurrent Xq duplication and 6q deletion, which was cryptic by G-banded analysis. FISH analyses with whole chromosome painting probes confirmed the imbalances and showed an unbalanced translocation der(6)t(X;6) in all three patients. A search in the literature revealed two additional pediatric patients with cryptic der(6)t(X;6) in t(12;21)-positive ALLs. No common break points on Xq or 6q could be determined between the five patients. This study highlights the importance of oaCGH analysis as an adjunct cytogenetic tool to detect cryptic chromosomal aberrations. Further, the study adds to understanding the full spectrum of secondary chromosomal aberrations in the very common t(12;21)-positive pediatric ALL disease group. We suggest that the unbalanced der(6)t(X;6), which is cryptic to conventional cytogenetics, is a non-random secondary event in this disease group. It might be that the specific combination of concurrent Xq duplication and 6q-deletion results in gain of possible oncogenes on Xq and loss of possible tumor suppressor genes on 6q that are important for the leukemic propagation of t(12;21)-positive hematopoietic cells in a subset of ALLs.

Human embryonic stem cells carrying an unbalanced translocation demonstrate impaired differentiation into trophoblasts: an in vitro model of human implantation failure.

Carriers of the balanced translocation t(11;22), the most common reciprocal translocation in humans, are at high risk of creating gametes with unbalanced translocation, leading to repeated miscarriages. Current research models for studying translocated embryos and the biological basis for their implantation failure are limited. The aim of this study was to elucidate whether human embryonic stem cells (hESCs) carrying the unbalanced chromosomal translocation t(11;22) can provide an explanation for repeated miscarriages of unbalanced translocated embryos. Fluorescent in situ hybridization and karyotype analysis were performed to analyze the t(11;22) in embryos during PGD and in the derived hESC line. The hESC line was characterized by RT-PCR and FACS analysis for pluripotent markers. Directed differentiation to trophoblasts was carried out by bone morphogenetic protein 4 (BMP4). Trophoblast development was analyzed by measuring ß-hCG secretion, by ß-hCG immunostaining and by gene expression of trophoblastic markers. We derived the first hESC line carrying unbalanced t(11;22), which showed the typical morphological and molecular characteristics of a hESC line. Control hESCs differentiated into trophoblasts secreted increasing levels of ß-hCG and concomitantly expressed the trophoblast genes, CDX2, TP63, KRT7, ERVW1, CGA, GCM1, KLF4 and PPARG. In contrast, differentiated translocated hESCs displayed reduced and delayed secretion of ß-hCG concomitant with impaired expression of the trophoblastic genes. The reduced activation of trophoblastic genes may be responsible for the impaired trophoblastic differentiation in t(11;22)-hESCs, associated with implantation failure in unbalanced t(11;22) embryos. Our t(11;22) hESCs are presented as a valuable human model for studying the mechanisms underlying implantation failure.

Approach to the Patient: Diagnosis and Treatment with Growth Hormone of Turner Syndrome and its Variants.

CONTEXT: Turner syndrome (TS) is characterized by a partial or complete absence of the second X chromosome in female. Here, patients with Xp deletion involving SHOX haploinsufficiency caused by unbalanced X-autosome translocations were discussed and considered as TS variants. OBJECTIVE: This work aimed to expand the current knowledge of TS and unbalanced X-autosome translocations and to suggest the definition, clinical characteristics, diagnosis workflow and growth hormone (GH) treatment strategy of TS and its variants. METHODS: A 9.0-year-old patient of TS variant with tall target height (+2.03SD) but low height velocity (3.6cm/y) and height (-1.33SD) was evaluated as an example. Patients similar to the index patient were systematically searched in MEDLINE and EMBASE and summarized. A diagnosis workflow and scores for risk assessment of GH treatment (RiGHT scores) for TS variants were also proposed in this study. RESULTS: According to the diagnosis workflow, the girl's karyotype was confirmed as 46,X,der(X)t(X;7)(p11.3; p14.1), and was evaluated as low risk using RiGHT scores. After 2-year GH treatment, she had a significantly increased height (-0.94SD). Moreover, a total of 13 patients from 10 studies were summarized, characterized as short stature, growth retardation, craniofacial abnormalities, disorders of intellectual development, and psychomotor delays. Risk assessment of GH treatment using RiGHT scores were also applied in these 13 patients. CONCLUSION: The patients with Xp deletion caused by unbalanced X-autosome translocations should be considered as TS variants. The diagnosis workflow and RiGHT scores is a useful approach for clinicians in addressing complex cases of TS variants with GH treatment in clinical practice.

Genetic counseling of mosaicism for balanced or unbalanced translocation with a normal cell line at amniocentesis.

Genetic counseling of mosaicism for balanced translocation with a normal cell line at amniocentesis is not difficult because most of the reported cases have normal phenotypes. However, genetic counseling of mosaicism for unbalanced translocation with a normal cell line at amniocentesis remains difficult because cases with mosaic unbalanced translocation with a normal cell line at prenatal diagnosis have been reported to be associated with either normal or abnormal phenotype. This article makes a comprehensive review of the reported cases of de novo or familial mosaic unbalanced translocation with a normal cell line and various counseling issues such as meiotic event, post-zygotic mitotic event, culture artefact, chimerism, uniparental disomy (UPD), jumping translocation, cytogenetic discrepancy between cultured and uncultured amniocytes and among various tissues, perinatal progressive decrease of the unbalanced translocation cell line and a possible favorable fetal outcome. The information provided is useful for obstetricians and genetic counselors during genetic counseling of the parents who wish to keep the babies under such a circumstance.

Non-Invasive Prenatal Test Analysis Opens a Pandora's Box: Identification of Very Rare Cases of SRY-Positive Healthy Females, Segregating for Three Generations Thanks to Preferential Inactivation of the XqYp Translocated Chromosome.

The translocation of the testis-determining factor, the SRY gene, from the Y to the X chromosome is a rare event that causes abnormalities in gonadal development. In all cases of males and females carrying this translocation, disorder of sex development is reported. In our study, we described a peculiar pedigree with the first evidence of four healthy females from three generations who are carriers of the newly identified t(X;Y)(q28;p11.2)(SRY+) translocation with no evidence of ambiguous genitalia or other SRY-dependent alterations. Our study was a consequence of a Non-Invasive Prenatal Test (NIPT) showing a sexual chromosomal abnormality (XXY) followed by a chorionic villus analysis suggesting a normal karyotype 46,XX and t(X;Y) translocation detected by FISH. Here, we (i) demonstrated the inheritance of the translocation in the maternal lineage via karyotyping and FISH analysis; (ii) characterised the structural rearrangement via chromosomal microarray; and (iii) demonstrated, via Click-iT® EdU Imaging assay, that there was an absolute preferential inactivation of the der(X) chromosome responsible for the lack of SRY expression. Overall, our study provides valuable genetic and molecular information that may lead personal and medical decisions.

Mosaic distal 13q duplication due to mosaic unbalanced translocation of 46,XY,der(14)t(13;14)(q32.2;p13)/46,XY at amniocentesis in a pregnancy associated with a favorable fetal outcome, perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes.

OBJECTIVE: We present mosaic distal 13q duplication due to mosaic unbalanced translocation 46,XY,der(14)t(13;14)(q32.2;p13)/46,XY at amniocentesis in a pregnancy associated with a favorable fetal outcome. CASE REPORT: A 37-year-old, gravida 2, para 0, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY, add(14) (p13)[17]/46,XY[13] (56.6% mosaicism). Array comparative genomic hybridization (aCGH) analysis on the DNA extracted from cultured amniocytes revealed arr 13q32.2q34 × 2∼3, consistent with 45% mosaicism for distal 13q duplication. Repeat amniocentesis at 24 weeks of gestation revealed a karyotype of 46,XY,der(14)t(13;14)(q32.2;p13)[14]/46,XY[16] (46.6% mosaicism). The parental karyotypes were normal. aCGH analysis on the DNA extracted from uncultured amniocytes revealed arr 13q32.2q34 × 2.38, consistent with 30-40% mosaicism for distal 13q duplication. Interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes detected 22.8% (23/101 cells) mosaicism for distal 13q duplication. Prenatal ultrasound findings were unremarkable. At 39 weeks of gestation, a 3616-g phenotypically normal baby was delivered. The karyotypes of cord blood, umbilical cord and placenta were 46,XY,der(14)t(13;14)(q32.2;p13)[20]/46,XY[20] (50% mosaicism), 46,XY,der(14)t(13;14)(q32.2;p13)[14]/46,XY[26] (35% mosaicism) and 46,XY (40/40 cells) (0% mosaicism), respectively. When follow-ups at the age of 4½ months and the age of one year, the peripheral blood had the karyotype of 46,XY,der(14)t(13;14)(q32.2;p13)[18]/46,XY[22] (45% mosaicism). Interphase FISH analysis on buccal mucosal cells at the age of 4½ months revealed 2.7% (3/110 cells) mosaicism for distal 13q duplication, compared with 1% (1/100 cells) in the normal control. The neonate was normal in phenotype and development. CONCLUSIONS: Mosaic unbalanced translocation at amniocentesis can be associated with a favorable fetal outcome, perinatal progressive decrease of the aneuploid cell line and cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes.

Optical Genome Mapping Identifies a Novel Unbalanced Translocation Between Chromosomes 4q and 6q Leading to Feeding Difficulties and Hypotonia in a Neonate: A Case Report.

Optical Genome Mapping (OGM) technology has garnered growing interest for the identification of chromosomal structural variations (SVs), particularly complex ones that are implicated in genetic diseases in humans. In this study, we performed genetic diagnostics on a neonatal patient who presented with feeding difficulties, hypotonia, and an atrial septal defect. We utilized a combination of trio-whole exome sequencing and OGM for our analysis. The results revealed an unbalanced translocation between maternal chromosomes 4 and 6 in the proband, ogm[GRch38]t(4:6)(q35.2;q25.3), resulting in a 2.8 Mb deletion at the 4q35 terminal and a 10.2 Mb duplication at the 6q25 terminal. In summary, this study highlights how OGM, in conjunction with other genetic approaches, can unveil the genetic etiology of complex clinical syndromes. Neonatal patients often exhibit low specific phenotypes, underlining the significance of SV detection.

Breaking new ground: Exploring de novo chromosomal rearrangements in 1p36 microdeletion.

Chromosomal structural variations (SVs) are linked to a wide range of phenotypes and arise due to disruptions during DNA replication, which can affect gene function within the SV regions. This case report details a patient diagnosed with neurodevelopmental delay. Detailed investigation through array comparative genomic hybridization revealed two pathogenic SVs on chromosome 1, which align with a 1p36 microdeletion, and a microduplication at 2p35.3, the latter being classified as a variant of unknown significance. The patient's clinical presentation is consistent with the 1p36 deletion syndrome, characterized by specific developmental delays and physical anomalies. Further genetic analysis suggests that these terminal rearrangements might stem from an unbalanced translocation between the short arms of chromosomes 1 and 2. This case underscores the complexity of interpreting multiple concurrent SVs and their cumulative effect on phenotype. Ongoing research into such chromosomal abnormalities will enhance our understanding of their clinical manifestations and guide more targeted therapeutic strategies.

A rare case of a mosaic unbalanced translocation after chorionic villous sampling.

BACKGROUND: Most of the literature suggests that unbalanced chromosomal translocations may lead to poor obstetrical outcomes. We present a case of an unbalanced translocation resulting in trisomy 1q and partial monosomy 20p identified on chorionic villous sampling (CVS). METHOD: Case report with expert-derived clinical management and guidance. RESULTS: After the abnormal CVS result, a subsequent amniocentesis revealed a normal 46,XX fetal karyotype. Detailed second trimester ultrasound of the fetus revealed no gross structural abnormalities. The CVS karyotype results were attributed to confined placental mosaicism (CPM) of the unbalanced translocation. The infant is 18 months old and has normal phenotype and karyotype. CONCLUSION: We recommend that if CPM with an unbalanced translocation is diagnosed on CVS, parental karyotype and an amniocentesis should be offered in conjunction with genetic counseling. In rare instances, such as this one, an unbalanced translocation may have a favorable outcome.

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.

Outcomes of two different unbalanced segregations from a maternal t(4;10)(q33;p15.1) translocation.

BACKGROUND: Unbalanced translocations can cause developmental delay (DD), intellectual disability (ID), growth problems, dysmorphic features, and congenital anomalies. They may arise de novo or may be inherited from a parent carrying a balanced rearrangement. It is estimated that 1/500 people is a balanced translocation carrier. The outcomes of different chromosomal rearrangements have the potential to reveal the functional consequences of partial trisomy or partial monosomy and can help guide genetic counseling for balanced carriers, and other young patients diagnosed with similar imbalances. METHODS: We performed clinical phenotyping and cytogenetic analyses of two siblings with a history of developmental delay (DD), intellectual disability (ID) and dysmorphic features. RESULTS: The proband, a 38-year-old female, has a history of short stature, dysmorphic features and aortic coarctation. She underwent chromosomal microarray analysis, which identified partial monosomy of 4q and partial trisomy of 10p. Her brother, a 37-year-old male, has a history of more severe DD, behavioral problems, dysmorphic features, and congenital anomalies. Subsequently, karyotype confirmed two different unbalanced translocations in the siblings: 46,XX,der(4)t(4;10)(q33;p15.1) and 46,XY,der(10)t(4;10)(q33;p15.1), respectively. These chromosomal rearrangements represent two possible outcomes from a parent who is a carrier for a balanced translocation 46,XX,t(4;10)(q33;p15.1). CONCLUSION: To our knowledge, this 4q and 10p translocation has not been described in literature. In this report we compare clinical features due to the composite effects of partial monosomy 4q with partial trisomy 10p and partial trisomy 4q with partial monosomy 10p. These findings speak to the relevance of old and new genomic testing, the viability of these segregation outcomes, and need for genetic counseling.

Characterization of a rare mosaic unbalanced translocation of t(3;12) in a patient with neurodevelopmental disorders.

BACKGROUND: Unbalanced translocations may be de novo or inherited from one parent carrying the balanced form and are usually present in all cells. Mosaic unbalanced translocations are extremely rare with a highly variable phenotype depending on the tissue distribution and level of mosaicism. Mosaicism for structural chromosomal abnormalities is clinically challenging for diagnosis and counseling due to the limitation of technical platforms and complex mechanisms, respectively. Here we report a case with a tremendously rare maternally-derived mosaic unbalanced translocation of t(3;12), and we illustrate the unreported complicated mechanism using single nucleotide polymorphism (SNP) array, fluorescence in situ hybridization (FISH), and chromosome analyses. CASE PRESENTATION: An 18-year-old female with a history of microcephaly, pervasive developmental disorder, intellectual disability, sensory integration disorder, gastroparesis, and hypotonia presented to our genetics clinic. She had negative karyotype by parental report but no other genetic testing performed previously. SNP microarray analysis revealed a complex genotype including 8.4 Mb terminal mosaic duplication on chromosome 3 (3p26.3->3p26.1) with the distal 5.7 Mb involving two parental haplotypes and the proximal 2.7 Mb involving three parental haplotypes, and a 6.1 Mb terminal mosaic deletion on chromosome 12 (12p13.33->12p13.31) with no evidence for a second haplotype. Adjacent to the mosaic deletion is an interstitial mosaic copy-neutral region of homozygosity (1.9 Mb, 12p13.31). The mother of this individual was confirmed by chromosome analysis and FISH that she carries a balanced translocation, t(3;12)(p26.1;p13.31). CONCLUSION: Taken together, the proband, when at the stage of a zygote, likely carried the derivative chromosome 12 from this translocation, and a postzygotic mitotic recombination event occurred between the normal paternal chromosome 12 and maternal derivative chromosome 12 to "correct" the partial 3p trisomy and partial deletion of 12p. To the best of our knowledge, it is the first time to report the mechanism utilizing a combined cytogenetic and cytogenomic approach, and we believe it expands our knowledge of mosaic structural chromosomal disorders and provides new insight into clinical management and genetic counseling.