Robertsonian translocations: an overview of 872 Robertsonian translocations identified in a diagnostic laboratory in China

A working model for the formation of Robertsonian chromosomes

Robertsonian chromosomes form by fusion of two chromosomes that have centromeres located near their ends, known as acrocentric or telocentric chromosomes. This fusion creates a new metacentric chromosome and is a major mechanism of karyotype evolution and speciation. Robertsonian chromosomes are common in nature and were first described in grasshoppers by the zoologist W. R. B. Robertson more than 100 years ago. They have since been observed in many species, including catfish, sheep, butterflies, bats, bovids, rodents and humans, and are the most common chromosomal change in mammals. Robertsonian translocations are particularly rampant in the house mouse, Mus musculus domesticus, where they exhibit meiotic drive and create reproductive isolation. Recent progress has been made in understanding how Robertsonian chromosomes form in the human genome, highlighting some of the fundamental principles of how and why these types of fusion events occur so frequently. Consequences of these fusions include infertility and Down's syndrome. In this Hypothesis, I postulate that the conditions that allow these fusions to form are threefold: (1) sequence homology on non-homologous chromosomes, often in the form of repetitive DNA; (2) recombination initiation during meiosis; and (3) physical proximity of the homologous sequences in three-dimensional space. This Hypothesis highlights the latest progress in understanding human Robertsonian translocations within the context of the broader literature on Robertsonian chromosomes.

A Retrospective Analysis of Robertsonian Translocations from a Single Center in China

Robertsonian translocations (ROBs) are the most common structural chromosomal abnormalities in the general population, with an estimated incidence rate of 1/1000 births. In this study, we retrospectively analyzed the cases of ROBs from September 2015 to August 2022 and totally identified ROB carriers from 84,569 specimens karyotyped in a single accredited laboratory in China, including 189 cases of balanced ROBs and 3 of mosaic ROBs. Microsoft Excel and descriptive statistics were used to record and analyze the collected data. The male/female ratio of ROBs is 1/1.29, with der(13;14) and der(14;21) being the main karyotypes. Among the 192 patients, 7 were lost to follow-up, 82 had given birth, and 103 were childless (such as miscarriage, fetal chromosomal abnormalities, in vitro fertilization (IVF) failure, or divorce). A total of 44 amniocenteses were performed in 42 couples; ROB cases with natural pregnancies showed that the normal karyotype and balanced ROBs of fetal accounted for 66.67% (16/24), while the results of assisted pregnancies showed 90.00% (18/20). This study represents the largest collections of ROBs in Jiangxi population and reminder that the ROB carriers can achieve the ideal outcome for pregnancy with the appropriate genetic guidance and assisted reproductive technologies (ART).

Cytogenetic status of patients with congenital malformations or suspected chromosomal abnormalities in Turkey: a comprehensive cytogenetic survey of 11,420 patients

Cytogenetic analysis is helpful in diagnostic workup of patients having prenatal or early postnatal medical problems and provides a basis for genetic counseling or deciding on clinical treatment options. Chromosomal abnormalities (CAs) constitute one of the most important category of genetic defects which have the potential to cause irreversible disorders. In this study, chromosome analysis results of 11,420 patients having congenital malformations or suspected of having chromosomal abnormalities, who were referred to Çukurova University Research and Training Hospital Cytogenetic Laboratory over a 16-year period, were investigated, retrospectively. Of all patients analyzed, CAs were found in 1768 cases, accounting for 15.5% of all cases. It was observed that 1175 (15.5%) of CAs were numerical (10.3%) and 593 (5.2%) were structural chromosome abnormalities. Among numerical CAs, Down syndrome (DS), Turner syndrome (TS) and Klinefelter syndrome (KS) constituted common categories which were observed in 7, 1.1 and 0.9% of all cases, respectively. Among the structural CAs, translocations, inversions, fragilities, deletions,, and others were the most common categories and constituted 2.2, 0.9, 0.9, 0.7, 0.3, and 0.3% of all cases, respectively. The sex ratio (male/female) of all cases was 1.01 and of DS cases was 1.6. Our results further confirmed that cytogenetic analysis is necessary in terms of making definite diagnosis of genetic disorders, providing proper genetic counseling and clinical treatment, assessing the recurrence risk, and preventing the hereditary genetic diseases and disorders. Besides, such studies will greatly assist in constituting national and international databases or records of genetic disorders.

A Balanced Robertsonian Translocation in a Patient with a Janus Kinase 2-Positive Polycythemia Vera

A male patient with a persistent, combined erythrocytosis, leukocytosis, and thrombocytosis without representative evidence of reactive increase emerged as having a myeloproliferative disorder. Molecular-biological assessment yielded Janus kinase 2-positive results, and the patient was diagnosed with polycythemia vera. In addition to these findings, further karyotyping accounted for a Robertsonian translocation. Because this rearrangement was a balanced variant, we concluded that this cytogenetic result might not significantly alter the diagnosis of polycythemia vera.

A Case-Control Study on Chromosomal Anomalies in Parents Experiencing Repeated Spontaneous Abortions From Northern India

Objectives

Many women lose their fetuses through miscarriage due to a variety of causes. The incidence of three or more consecutive pregnancy losses is often classified as repeated spontaneous abortion (RSA) and is considered the most frustrating and complex area in reproductive medicine. Parental chromosomal abnormalities, underlying medical condition, heritable or acquired thrombophilias, immunologic abnormalities, infections, and environmental factors are reported to be possible etiologies responsible for RSA. Gametes with unbalanced chromosomes, which are formed when abnormalities exist in parent chromosomes, are one such cause and are responsible for about 50-60% of first-trimester pregnancy loss. This paper aims to identify whether there is an association between chromosomal anomalies in parents and RSA.

Method

A case-control study was performed on a total sample size of 600 individuals, including 150 couples with a history of RSA and 150 fertile couples as control. The participants were cytogenetically analyzed using G-banding. Associations between variables were tested using Chi-square and Fisher’s exact test (a p-value<0.05 was considered significant). Informed consent from participants and institutional ethical clearance was obtained before the research began.

Results

Chromosomal anomalies were detected in 21 individuals (7%) with a history of RSA. Female preponderance was observed with a female to male ratio of 2.5:1. Structural chromosomal aberrations (SCAs) were detected in 17 patients, with nine (53%) cases showing balanced reciprocal translocation (involving chromosomes 1,3,6,8,12,13,15,16,18,22 and X) and three (17.65%) cases of Robertsonian translocation (exclusively in males). Mosaicism was observed in four (19.05%) cases. A statistically significant positive association (p-value <0.05) was observed between the presence of parental chromosomal anomalies and RSA.

Conclusion

These results support an association between RSA and parental chromosomal abnormalities. Currently, clinicians treating cases of RSA face challenging clinical conditions. Identifying a cytogenetic cause for RSA may be of great help to clinicians who manage affected couples.

Canary in the Coal Mine? Male Infertility as a Marker of Overall Health

Male factor infertility is a common problem. Evidence is emerging regarding the spectrum of systemic disease and illness harbored by infertile men who otherwise appear healthy. In this review, we present evidence that infertile men have poor overall health and increased morbidity and mortality, increased rates of both genitourinary and non-genitourinary malignancy, and greater risks of systemic disease. The review also highlights numerous genetic conditions associated with male infertility as well as emerging translational evidence of genitourinary birth defects and their impact on male infertility. Finally, parallels to the overall health of infertile women are presented. This review highlights the importance of a comprehensive health evaluation of men who present for an infertility assessment.

Pregnancy-Related Extracellular Vesicles Revisited

Extracellular vesicles (EVs) are small vesicles ranging from 20–200 nm to 10 μm in diameter that are discharged and taken in by many different types of cells. Depending on the nature and quantity of their content—which generally includes proteins, lipids as well as microRNAs (miRNAs), messenger-RNA (mRNA), and DNA—these particles can bring about functional modifications in the receiving cells. During pregnancy, placenta and/or fetal-derived EVs have recently been isolated, eliciting interest in discovering their clinical significance. To date, various studies have associated variations in the circulating levels of maternal and fetal EVs and their contents, with complications including gestational diabetes and preeclampsia, ultimately leading to adverse pregnancy outcomes. Furthermore, EVs have also been identified as messengers and important players in viral infections during pregnancy, as well as in various congenital malformations. Their presence can be detected in the maternal blood from the first trimester and their level increases towards term, thus acting as liquid biopsies that give invaluable insight into the status of the feto-placental unit. However, their exact roles in the metabolic and vascular adaptations associated with physiological and pathological pregnancy is still under investigation. Analyzing peer-reviewed journal articles available in online databases, the purpose of this review is to synthesize current knowledge regarding the utility of quantification of pregnancy related EVs in general and placental EVs in particular as non-invasive evidence of placental dysfunction and adverse pregnancy outcomes, and to develop the current understanding of these particles and their applicability in clinical practice.

Analysis of sperm chromosomes in six carriers of rare and common Robertsonian translocations

Introduction: Robertsonian translocation (RobT) is the central fusion of the long arms of two acrocentric chromosomes, leading to 45 chromosomes in humans. The most common ones are rob(13;14) and rob(14;21) (91%). Other types of RobT are so-called rare cases. In the general population RobTs occur with a frequency of approximately 0.123%, but among men with reproductive failure this value rises 9-fold. Infertility in RobT carriers is associated with the formation of unbalanced spermatozoa resulting from segregation of the chromosomes involved in trivalent during the meiotic prophase. In spermatozoa of many RobT carriers an increased level of chromosomal aneuploidy is observed. Materials and Methods: We examined the hyperhaploidy level of chromosomes 7, 9, 18, 21, 22, X and Y in spermatozoa of 6 RobT unrelated carriers: two carriers with rare rob(13;15), one with rare rob(13;22), and three of the common rob(13;14). Results were compared with the control data from a group of 7 fertile men with a normal karyotype. Fluorescent in situ hybridization (FISH) was applied. Results: We found an increased level of sperm aneuploidy regarding at least one of the analyzed chromosomes in each of the carriers, while in rare RobTs interchromosomal effect (ICE) was observed. Meiotic segregation pattern of a rare rob(13;15) carrier revealed the 76% of normal /balanced spermatozoa. Disucussion: Due to the relatively high population frequency of RobTs, their influence on reproductive failure, hight risk of imbalancement in prenatal diagnosis (7%), and small amount of data for rare RobTs, each newly characterized case is valuable in genetic counseling.

Prevalence and Phenotypic Impact of Robertsonian Translocations

Robertsonian translocations (RTs) result from fusion of 2 acrocentric chromosomes (e.g., 13, 14, 15, 21, 22) and consequential losses of segments of the p arms containing 47S rDNA clusters and transcription factor binding sites. Depending on the position of the breakpoints, the size of these losses vary considerably between types of RTs. The prevalence of RTs in the general population is estimated to be around 1 per 800 individuals, making RTs the most common chromosomal rearrangement in healthy individuals. Based on their prevalence, RTs are classified as "common," rob(13;14) and rob(14;21), or "rare" (the 8 remaining nonhomologous combinations). Carriers of RTs are at an increased risk for offspring with chromosomal imbalances or with uniparental disomy. RTs are generally regarded as phenotypically neutral, although, due to RTs formation, 2 of the 10 ribosomal rDNA gene clusters, several long noncoding RNAs, and in the case of RTs involving chromosome 21, several mRNA encoding genes are lost. Nevertheless, recent evidence indicates that RTs may have a significant phenotypic impact. In particular, rob(13;14) carriers have a significantly elevated risk for breast cancer. While RTs are easily spotted by routine karyotyping, they may go unnoticed if only array-CGH and NextGen sequencing methods are applied. This review first discusses possible molecular mechanisms underlying the particularly high rates of RT formation and their incidence in the general population, and second, likely causes for the elevated cancer risk of some RTs will be examined.

How much, if anything, do we know about sperm chromosomes of Robertsonian translocation carriers?

In men with oligozoospermia, Robertsonian translocations (RobTs) are the most common type of autosomal aberrations. The most commonly occurring types are rob(13;14) and rob(14;21), and other types of RobTs are described as 'rare' cases. Based on molecular research, all RobTs can be broadly classified into Class 1 and Class 2. Class 1 translocations produce the same breakpoints within their RobT type, but Class 2 translocations are predicted to form during meiosis or mitosis through a variety of mechanisms, resulting in variation in the breakpoint locations. This review seeks to analyse the available data addressing the question of whether the molecular classification of RobTs into Classes 1 and 2 and/or the type of DD/GG/DG symmetry of the involved chromosomes is reflected in the efficiency of spermatogenesis. The lowest frequency value calculated for the rate of alternate segregants was found for rob(13;15) carriers (Class 2, symmetry DD) and the highest for rob(13;21) carriers (Class 2, DG symmetry). The aneuploidy values for the rare RobT (Class 2) and common rob(14;21) (Class 1) groups together exhibited similarities while differing from those for the common rob(13;14) (Class 1) group. Considering the division of RobT carriers into those with normozoospermia and those with oligoasthenozoospermia, it was found that the number of carriers with elevated levels of aneuploidy was unexpectedly quite similar and high (approx. 70%) in the two subgroups. The reason(s) that the same RobT does not always show a similar destructive effect on fertility was also pointed out.

The Interchromosomal Effect: Different Meanings for Different Organisms

The term interchromosomal effect was originally used to describe a change in the distribution of exchange in the presence of an inversion. First characterized in the 1920s by early Drosophila researchers, it has been observed in multiple organisms. Nearly half a century later, the term began to appear in the human genetics literature to describe the hypothesis that parental chromosome differences, such as translocations or inversions, may increase the frequency of meiotic chromosome nondisjunction. Although it remains unclear if chromosome aberrations truly affect the segregation of structurally normal chromosomes in humans, the use of the term interchromosomal effect in this context persists. This article explores the history of the use of the term interchromosomal effect and discusses how chromosomes with structural aberrations are segregated during meiosis.

Study of Spectrum of Chromosomal Rearrangements in Recurrent Pregnancy Loss

Introduction

Recurrent pregnancy losses (RPLs) are seen in up to 15-20% of all clinically recognized pregnancies, 1-2% of women in general population. Repeated losses are seen in 5-10% of women. The prevalence of chromosomal rearrangements is 6.65% in couples with repeated pregnancy losses. Two to 4% of RPL are associated with parental balanced reciprocal and Robertsonian translocations.

Materials and Methods

The study was conducted at a tertiary care hospital in New Delhi, and in total, 204 couples with RPL enrolled in the study.

Results

In total, 4490 couples presented to the obstetric clinic, of which 204 (4.5%) couples had repeated pregnancy losses. Cytogenetic analysis was done in 198 couples. Out of total 198 patients, 14 patients (7.1%) had cytogenetic alterations. Most common aberrations observed were structural rearrangements, of which reciprocal translocations were more common. In our study cohort, all the couples had maternal age of ≤ 35 years and all the alterations were seen either in mother or in both parents.

Discussion

Our study highlights that cytogenetic alterations not only are common in first trimester miscarriages, but are an important event in miscarriages presenting at later period of gestation and in young mothers as well.

Chromosomal segregation in sperm of the Robertsonian translocation (21;22) carrier and its impact on IVF outcome

PURPOSE

To assess the variability of meiotic segregation patterns in sperm of Robertsonian translocation (RobT) carrier t(21;22) and present effect on reproductive outcome.

METHODS

Infertile couple enrolled in IVF/ICSI program. Sperm chromosomal segregation analysis was done using FISH; preimplantation genetic testing for aneuploids (PGT-A) was performed by NGS.

RESULTS

Patients had a low fertilization rate and a negative outcome after the first IVF/ICSI cycle, so they were advised to do chromosomal aberration analysis before their next attempt. The second IVF/ICSI procedure resulted in pregnancy, and two blastocysts were cryopreserved. The NIFTY test has shown low risk for all tested trisomies, sex chromosomes aneuploidis, and deletion syndromes, so a healthy female child was born. During pregnancy, karyotypisation results revealed that the male partner is a RobT carrier t(21;22). Sperm segregation analysis of chromosomes 21 and 22 has shown six types of sperm chromosome sets. The majority of sperm cells had a normal/balanced RobT form of a haploid set of chromosomes (68.5-76%) called an "alternate." Sperm cells that had additional chromosome 21 or 22, or lack of chromosome 21 or 22, were present in 4-12%. PGT-A performed on two cryopreserved blastocysts revealed one embryo euploid and the other with the mosaic aneuploidy of chromosome 7 present in 50% of the cells.

CONCLUSION

Infertile couples with a RobT male carrier who have semen comprising of normal/alternate form in the majority have a good prognosis of IVF/ICSI outcome. PGT is recommended because of the possible occurrence of viable trisomic embryos and potential interchromosomal effect.

Unexpected Coexistence of a Derivative t(21;21) and Complementary Mosaic r(21) in a Female with Multiple Miscarriages

The case presented here describes a female patient with recurrent miscarriages and a normal microarray analysis result. However, the coexistence of a robertsonian (21;21) translocation and complementary mosaic ring chromosome 21 was detected by karyotyping and FISH analysis. Partial trisomy 21 was found with QF-PCR and microarray analysis in one of the fetuses. The aim of this report was to emphasize the diagnostic importance of conventional cytogenetics.

The Frequency and Spectrum of Chromosomal Translocations in a Cohort of Sri Lankans

Translocations are the most common type of structural chromosomal abnormalities. Unbalanced translocations are usually found in children who present with congenital abnormalities, developmental delay, or intellectual disability. Balanced translocations are usually found in adults who frequently present with reproductive failure; either subfertility, or recurrent pregnancy loss. Herein, we report the spectrum and frequency of translocations in a Sri Lankan cohort. A database of patients undergoing cytogenetic testing was maintained prospectively from January 2007 to December 2016 and analyzed, retrospectively. A total of 15,864 individuals were tested. Among them, 277 (1.7%) had translocations. There were 142 (51.3%) unbalanced translocations and 135 (48.7%) balanced translocations. Majority (160; 57.8%) were Robertsonian translocations. There were 145 (52.3%) children and adolescents aged less than 18 years with translocations, and 142 (97.9%) were unbalanced translocations. Majority [138 (95.2%)] were referred due to congenital abnormalities, developmental delay, or intellectual disability, and 91 were children with translocation Down syndrome. All adults aged 18 years or above (132) had balanced translocations. Subfertility and recurrent pregnancy loss [84 (63.6%)] and offspring(s) with congenital abnormalities [48 (36.4%)] were the most common indications in this group. Majority (68.2%) in this group were females with reciprocal translocations (55.3%). Chromosomes 21, 14, and 13 were the most commonly involved with rob(14q21q) [72 (26%)], rob(21q21q) [30 (13.7%)], and rob(13q14q) [34 (12.3%)] accounting for 52% of the translocations. Chromosomes 1, 8, 11, and 18 were most commonly involved in reciprocal translocations. The observed high frequency of chromosomal translocations in our cohort highlights the importance of undertaking cytogenetic evaluation and providing appropriate genetic counseling for individuals with the phenotypes associated with these translocations.

Non-Robertsonian translocations involving chromosomes 13, 14, or 15 in male infertility: 28 cases and a review of the literature

For genetic counseling of male carriers of chromosomal translocations, the specific chromosomes and breakpoints involved in the translocation are relevant to know. The structural chromosomal abnormalities may lead to abnormal sperm counts, infertility, and miscarriage. These are related to the specific chromosomes and breakpoints involved in the translocation. To date, over 200 cases of non-Robertsonian translocation in male carriers have been described that involve chromosomes 13, 14, or 15.This study reports of 28 male carriers from our clinic with balanced reciprocal translocations of chromosome 13, 14, or 15, and a literature review of 201 cases. The 28 male carriers from our clinic were diagnosed by cytogenetic analyses: 19 subjects suffered from pregestational infertility and 9 from gestational infertility. The most common translocations were t(7;13), t(10;14), and t(3;15), observed respectively in 13 (46%), 8 (29%), and 8 (29%) of our subjects. The literature cases (n = 201) involved chromosome 13 (n = 83, 41%), chromosome 14 (n = 56, 28%) or 15 (n = 62, 31%) in which 75 breakpoints were identified, the most common breakpoint, 13q22, was observed in 12 subjects (6%), followed by 14q32 (n = 11), 15q15 (n = 9), and 15q22 (n = 9). Most breakpoints were related to gestational infertility, while breakpoints at 13p13, 13p12, 13p11.2, 13p11, 13q11, 13q15, 14p12, 14p10, 15p13, 15p10, and 15q22.2 were associated with pregestational infertility.Carriers of non-Robertsonian translocations involving chromosome 13, 14, or 15 and experiencing infertility should receive counseling with regard to chromosomal breakpoints as there seem to be consequences for treatment. Intracytoplasmic sperm injection with preimplantation genetic diagnosis (PGD) for the carriers with oligozoospermia, microscopic testicular sperm extraction or sperm from the sperm bank for the carriers with azoospermia should be considered for pregestational infertility. The carriers with gestational infertility can choose PGD or prenatal diagnosis.

Mortality and Cancer Incidence in Carriers of Balanced Robertsonian Translocations: A National Cohort Study

A balanced robertsonian translocation (rob) results from fusion of 2 acrocentric chromosomes. Carriers are phenotypically normal and are often diagnosed because of recurrent miscarriages, infertility, or aneuploid offspring. Mortality and site-specific cancer risks in carriers have not been prospectively investigated. We followed 1,987 carriers diagnosed in Great Britain for deaths and cancer risk, over an average of 24.1 years. Standardized mortality and incidence ratios were calculated comparing the number of observed events against population rates. Overall mortality was higher for carriers diagnosed before age 15 years (standardized mortality ratio (SMR) = 2.00, 95% confidence interval (CI): 1.09, 3.35), similar for those diagnosed aged 15–44 years (SMR = 1.06, 95% CI: 0.86–1.28), and lower for those diagnosed aged 45–84 years (SMR = 0.81, 95% CI: 0.68, 0.95). Cancer incidence was higher for non-Hodgkin lymphoma (standardized incidence ratio (SIR) = 1.90, 95% CI: 1.01, 3.24) and childhood leukemia (SIR = 14.5, 95% CI: 1.75, 52.2), the latter particularly in rob(15;21) carriers (SIR = 447.8, 95% CI: 11.3, 2,495). Rob(13;14) carriers had a higher breast cancer risk (SIR = 1.58, 95% CI: 1.12, 2.15). Mortality risks relative to the population in diagnosed carriers depend on age at cytogenetic diagnosis, possibly reflecting age-specific cytogenetic referral reasons. Carriers might be at greater risk of childhood leukemia and non-Hodgkin lymphoma and those diagnosed with rob(13;14) of breast cancer.

The effect of Robertsonian translocations on the intranuclear positioning of NORs (nucleolar organizing regions) in human sperm cells

Only a few studies have described sperm chromosome intranuclear positioning changes in men with reproductive failure and an incorrect somatic karyotype. We studied the influence of Robertsonian translocations on the acrocentric chromosome positioning in human sperm cells. The basis of the analysis was the localization of NORs (nucleolar organizing regions) in sperm nuclei from three Robertsonian translocation carriers, namely, rob(13;22), rob(13;15) and rob(13;14), with a known meiotic segregation pattern. All three carriers presented with a similar percentage of genetically normal sperm cells (i.e., approximately 40%). To visualize NORs, we performed 2D-FISH with directly labelled probes. We used the linear and radial topologies of the nucleus to analyse the NORs distribution. We found an affected positioning of NORs in each case of the Robertsonian translocations. Moreover, the NORs tended to group, most often in two clusters. Both in Robertsonian carriers and control sperm cells, NORs mostly colocalized in the medial areas of the nuclei. In the case of the Roberstonian carriers, NORs were mostly concentrated in the peripheral part of the medial area, in contrast to control sperm cells in which the distribution was more dispersed towards the internal area.

The application of PGT-A for carriers of balanced structural chromosomal rearrangements

The aim of this study was to analyze differences in chromosomal aberrations and euploidy in embryos of each translocation type and gender of carrier in the case series of 10 couples with balanced translocations who underwent IVF with embryos trophectoderm (TE) biopsy and PGT-A to detect chromosomal aberrations. This is a Case Series (Retrospective study). In each case, controlled ovarian hyperstimulation, oocyte insemination with intracytoplasmic sperm injection (ICSI) and cultivation gave multiple blastocysts, that underwent trophectoderm (TE) biopsy with PGT-A analysis using aCGH and NGS. Number of total unbalanced translocations compared to the number of sporadic aneuploid embryos was 39.6% to 39.6% (50% to 50% of all 37 aneuploid embryos). The highest euploidy rate was in male carrier group - 26.7% and the lowest in the Robertsonian translocation carrier group - 18.2%. Sporadic aneuploidy - 68.2% was highest in Robertsonian translocation carrier group and lowest in female group - 11.1%. Chromosomal aberrations related to translocation were highest in female carrier group - 77.8% and lowest in Robertsonian translocation carrier group - 13.6%. Our study showed that expectancy of total embryo aneuploidy rates will be higher in carriers, than in people with normal karyotype. The prevalence of chromosomal aberrations related to translocation was 4.5 times higher in Reciprocal carrier group than in Robertsonian translocation carrier group. Among maternal and paternal carrier groups, the embryos from female carriers had the lowest euploidy rate, unbalanced translocation rate 4.7 times higher than in the male carrier group and higher total aneuploidy rates.

De novo Balanced Robertsonian Translocation rob(22;22)(q10;q10) in a Woman with Recurrent Pregnancy Loss: A Rare Case

BACKGROUND

Recurrent pregnancy loss (RPL), one of the most common complications of pregnancy, is responsible for significant emotional distress to the couple desiring to conceive. In almost 50% of the cases, the etiology remains unknown. The frequency of chromosomal structural rearrangements associated with a history of RPL in couples varies between 2% to 8%. Robertsonian translocations (ROBs) have an estimated incidence rate of 1/1000 births, making this type of rearrangement the most common structural chromosomal abnormalities seen in the general population. According to the literature, there are few RPL cases with rob (22;22).

CASE PRESENTATION

This case is a Syrian female offered to the Orient Hospital (Damascus, Syria), having RPL in the first trimester, no fetal malformations, and/or no neonatal death. She had a balanced chromosomal translocation involved the both short arms of chromosome 22. Banding cytogenetics, refined by array-proven multicolor banding (aMCB) revealed a rob (22; 22)(q10;q10). Her husband had a normal karyotype. Interestingly, chromosomal analysis was performed for her other family members and it revealed normal karyotype for all people, which indicates that translocation is of de novo origin. However, the couple did not have any living offspring after seven years of marriage.

CONCLUSION

The present case was a case of RPL occurring due to rob (22;22). However, the rob(22;22)(q10;10) is the cause of recurrent abortions. Couples with the history of RPL should be suggested to do cytogenetic analysis in order to estimate whether they have chromosomal rearrangement. This diagnostic approach is of great significance to figure out what causes RPL.