Trisomy 9: review and report of two new cases

Application of various genetic analysis techniques for detecting two rare cases of 9p duplication mosaicism during prenatal diagnosis

BACKGROUND

The identification of genetic mosaicism and the genetic counseling needed following its discovery have been challenging problems in the field of prenatal diagnosis. Herein, we describe the clinical phenotypes and various prenatal diagnostic processes used for two rare cases of 9p duplication mosaicism and review the prior literature in the field to evaluate the merits of different methods for diagnosing mosaic 9p duplication.

METHODS

We recorded ultrasound examinations, reported the screening and diagnosis pathways, and analyzed the mosaic levels of the two cases of 9p duplication using karyotype analysis, chromosomal microarray analysis (CMA), and fluorescence in situ hybridization analysis (FISH).

RESULTS

Case 1 had a normal clinical phenotype for tetrasomy 9p mosaicism, and Case 2 showed multiple malformations caused by both trisomy 9 and trisomy 9p mosaicism. Both cases were initially suspected after non-invasive prenatal screening (NIPT) based on cell-free DNA. The mosaic ratio of 9p duplication found via karyotyping was lower than what was discovered by CMA and FISH, in both cases. Contrary to previous findings, the mosaic level of trisomy 9 found by karyotype analysis was greater than what was found by CMA, in terms of complex mosaicism involving trisomy 9 and trisomy 9p, in Case 2.

CONCLUSION

NIPT can indicate 9p duplication mosaicism during prenatal screening. Different strengths and limitations existed in terms of diagnosing mosaic 9p duplication by karyotype analysis, CMA, and FISH. The combined use of various methods may be capable of more accurately determining break-points and mosaic levels of 9p duplication during prenatal diagnosis.

Case report: A case report and literature review of complete trisomy 9

Complete trisomy 9 is a rare and lethal chromosomal anomaly characterized by multisystem dysmorphism and central nervous system (CNS) malformations. This study presents a case of complete trisomy 9 with an unusual phenotypic association and investigates the genetic pathways involved in this chromosomal abnormality. Trisomy 9 leads to a wide range of organ abnormalities, and this research contributes to a better understanding of the phenotype associated with this rare aneuploidy. The literature on the phenotypes of fetuses with various systems affected by complete trisomy 9 was reviewed and summarized. Correct diagnosis and appropriate counseling based on the characteristics of previous reports of fetuses with trisomy 9 is essential in maternity care and clinical management. To provide guidance and help for clinical diagnosis, this study aimed to explore the clinical and genetic characteristics of trisomy 9 syndrome to improve clinicians' understanding of the disease.

The histone demthylase KDM3A protects the myocardium from ischemia/reperfusion injury via promotion of ETS1 expression

Our prior studies have characterized the participation of histone demethylase KDM3A in diabetic vascular remodeling, while its roles in myocardial ischemia/reperfusion (I/R) injury (MIRI) remain to be illustrated. Here we show that KDM3A was significantly downregulated in rat I/R and cellular hypoxia/reoxygenation (H/R) models. Subsequently, gain- and loss-of-function experiments were performed to investigate the effects of KDM3A in the settings of MIRI. KDM3A knockout exacerbated cardiac dysfunction and cardiomyocytes injury both in vivo and in vitro. The deteriorated mitochondrial apoptosis, reactive oxygen species, and inflammation were simultaneously observed. Conversely, KDM3A overexpression developed the ameliorated alternations in MIRI. Mechanistically, the MIRI-alleviating effects of KDM3A were associated with the enhancement of ETS1 expression. ChIP-PCR affirmed that KDM3A bound to the ETS1 promoter and removed dimethylation of histone H3 lysine 9 (H3K9me2), thus promoting ETS1 transcription. Our findings suggest that KDM3A is available for alleviating multi-etiologies of MIRI through the regulation of ETS1.

Prevention of cardiac injury requires a deeper mechanistic understanding of ischemia/reperfusion (I/R) episodes. Here, the authors find that the epigenetic modifier KDM3A plays a crucial role in myocardial I/R injury through its activation of the gene ETS1 and suggest boosting KDM3A expression could be a potential treatment strategy.

Trisomy 9 mosaic syndrome: Sixteen additional patients with new and/or less commonly reported features, literature review, and suggested clinical guidelines

Trisomy 9 mosaic syndrome (T9M) is a rare condition characterized by multiorgan system involvement including craniofacial dysmorphisms, cardiac, genitourinary (GU), skeletal, and central nervous system (CNS) abnormalities. Although more than 100 cases have been reported in the literature, a comprehensive review has not been performed nor have clinical guidelines been established. Therefore, we describe the clinical features of 16 additional patients, review features of previously reported individuals, and suggest clinical guidelines. Our findings expand the clinical phenotype of T9M, including novel features of amblyopia, astigmatism, corectopia of pupil, posterior embryotoxon, and diaphragmatic eventration. Most patients had prenatal and perinatal issues, particularly from respiratory, growth, and feeding standpoints. Although small birth parameters were common, long-term growth trends varied widely. An association with advanced parental ages was also identified. The spectrum of growth and development was wide, ranging from nonverbal patients to those able to participate in educational programs with age-appropriate peers. The severity of clinical outcomes was unrelated to blood lymphocyte mosaicism levels. Microarray analysis had a higher diagnostic rate compared to standard karyotype analysis and should be utilized if this diagnosis is suspected. Future longitudinal studies will be key to monitor long-term outcomes of individuals with T9M and determine best practices for clinical management.

A rare case of postnatal mosaic trisomy 12 with severe congenital heart disease and literature review

Trisomy 12 is a rare autosomal aneuploidy. All postnatally diagnosed individuals with trisomy 12 have been mosaic for this chromosome abnormality. We herein report an infant girl presented at 2 weeks of age with severe congenital heart defect, tracheobronchomalacia, and dysmorphic features. All of the dysmorphic features of this patient fit into the known phenotype spectrum of mosaic trisomy 12, although this patient uniquely presented with macrocephaly. Tracheo-bronchomalacia has been described once previously but had a significant impact on this patient's clinical course. The patient passed away at 2-month-old due to cardiac and respiratory complications. Chromosomal single nucleotide polymorphism (SNP) microarray analysis on a peripheral blood sample from the patient revealed trisomy 12 in approximately 50% of cells. Concurrent fluorescence in situ hybridization analysis of uncultured blood cells detected a comparable level of trisomy 12 mosaicism. Compared to conventional cytogenetics, SNP microarray examines all nucleated cells without sampling bias, has an increased power to estimate mosaicism level, and can provide a quick assessment of the underlying mechanism. Here we demonstrate the utilization of SNP microarray in the clinical diagnosis of those once considered rare disorders but might have been missed by conventional cytogenetic techniques.

The genetics of congenital heart disease… understanding and improving long-term outcomes in congenital heart disease: a review for the general cardiologist and primary care physician

PURPOSE OF REVIEW

This review has two purposes: to provide an updated review of the genetic causes of congenital heart disease (CHD) and the clinical implications of these genetic mutations, and to provide a clinical algorithm for clinicians considering a genetics evaluation of a CHD patient.

RECENT FINDINGS

A large portion of congenital heart disease is thought to have a significant genetic contribution, and at this time a genetic cause can be identified in approximately 35% of patients. Through the advances made possible by next generation sequencing, many of the comorbidities that are frequently seen in patients with genetic congenital heart disease patients can be attributed to the genetic mutation that caused the congenital heart disease. These comorbidities are both cardiac and noncardiac and include: neurodevelopmental disability, pulmonary disease, heart failure, renal dysfunction, arrhythmia and an increased risk of malignancy. Identification of the genetic cause of congenital heart disease helps reduce patient morbidity and mortality by improving preventive and early intervention therapies to address these comorbidities.

SUMMARY

Through an understanding of the clinical implications of the genetic underpinning of congenital heart disease, clinicians can provide care tailored to an individual patient and continue to improve the outcomes of congenital heart disease patients.

Partial trisomy 9: prenatal diagnosis and recurrence within same family

Trisomy 9 can be suspected and confirmed in the prenatal period since the 11–13.6 weeks of screening. In cases of partial trisomy 9, the diagnosis is important especially to counseling the couple due to the increased likelihood of recurrence in subsequent pregnancies.

Cardiac Failure in a Trisomy 9 Patient Undergoing Anesthesia: A Case Report

A 27-year-old female with Trisomy 9 mosaicism presented to Children's Hospital Colorado for outpatient dental surgery under general anesthesia. The patient's past medical history was also significant for premature birth, gastroesophageal reflux, scoliosis and kyphosis, obesity, and developmental delay. Per her mother's report, the patient had no cardiac issues. She had undergone multiple previous general anesthetics, some of which documented respiratory complications such as laryngospasm, bronchospasm, and possible aspiration. During this anesthetic, the patient became hypotensive on induction, with sluggish response to intravenous fluids, glycopyrrolate, and ephedrine. Her electrocardiogram demonstrated what appeared to be left bundle branch block at baseline, with possible ST segment changes after induction. Due to her abnormal reaction to the induction and subsequent treatment for hypotension, an echocardiogram was performed. The patient was found to have an ejection fraction of 25%-30%. The anesthetic was uneventful for the remainder of the procedure, and following recovery, the patient was admitted by the heart failure team for further care.

Report of a Case with Trisomy 9 Mosaicism

Trisomy 9 is a rare chromosome disorder with high neonatal mortality. It is often seen in mosaic form. Most patients who survive are severely mentally retarded. The main features of this syndrome are "bulbous" nose, microphthalmia, dislocated limbs, and other anomalies of skeletal, cardiac, genitourinary, and central nervous system. Most patients have developmental and cognitive impairment. Patients with mosaicism survive longer than non-mosaics, but it was believed that the degree of mosaicism in lymphocytes or fibroblasts does not associate with survival or degree of impairment. In this report, we present a 2.5-year-old male case of mosaic trisomy 9, to show the wide range of clinical findings in this chromosome disorder. The patient had cardiac anomalies, inguinal hernia, and undescendent testes. He had low-set slightly malformed ears, deeply-set malformed eyes, small palpebral fissures, micrognathia, developmental delay and unilateral optic hypoplasia. The most prominent facial anomaly in this patient was eye anomalies. Cytogenetic analysis with G banding showed karyotype 47XY,+9 in 44% of peripheral lymphocytes examined (47XY,+9[22], 46XY[28]). His parents' karyotypes were normal. Moderate developmental delay, which was detected in this patient shows that the range of motor and cognitive impairment in this chromosomal disorder is quite broad. This fact should be considered in genetic counseling as well as prenatal diagnosis of this chromosomal disorder.

Birth of a child with trisomy 9 mosaicism syndrome associated with paternal isodisomy 9: case of a positive noninvasive prenatal test result unconfirmed by invasive prenatal diagnosis

Background

Non-invasive prenatal testing (NIPT) is currently used as a frontline screening test to identify fetuses with common aneuploidies. Occasionally, incidental NIPT results are conveyed to the clinician suggestive of fetuses with rare chromosome disease syndromes. We describe a child with trisomy 9 (T9) mosaicism where the prenatal history reported a positive NIPT result for T9 that was unconfirmed by conventional prenatal diagnosis.

Methods

NIPT was performed by low coverage whole genome plasma DNA sequencing. Karyotyping and fluorescent in situ hybridization (FISH) analysis with chromosome 9p-ter and 9q-ter probes was used to determine the somatic cell level of T9 mosaicism in the fetus and child. Quantitative fluorescent PCR (Q-PCR) of highly polymorphic short tandem repeat (STR) chromosome 9 markers was also performed to investigate the nature of the T9 mosaicism and the parental origin.

Results

A 22 month old girl presented with severe developmental delay, congenital cerebral dysplasia and congenital heart disease consistent with phenotypes associated with T9 mosaicism syndrome. Review of the prenatal testing history revealed a positive NIPT result for chromosome T9. However, follow up confirmatory karyotyping and FISH analysis of fetal cells returned a normal karyotype. Post-natal studies of somatic cell T9 mosaicism by FISH detected levels of approximately 20 % in blood and buccal cells. Q-PCR STR analysis of family DNA samples suggested that the T9 mosaicism originated by post-zygotic trisomic rescue of a paternal meiotic II chromosome 9 non-disjunction error resulting in the formation of two distinct somatic cell lines in the proband, one with paternal isodisomy 9 and one with T9.

Conclusion

This study shows that NIPT may also be a useful screening technology to increase prenatal detection rates of rare fetal chromosome disease syndromes.

New report of two patients with mosaic trisomy 9 presenting unusual features and longer survival

CONTEXT

Mosaic trisomy 9 is considered to be a rare chromosomal abnormality with limited survival. Our objective was to report on two patients with mosaic trisomy 9 presenting unusual findings and prolonged survival.

CASE REPORTS

The first patient was a boy aged six years and five months presenting weight of 14.5 kg (< P3), height of 112 cm (P10), head circumference of 49 cm (P2), prominent forehead, triangular and asymmetric face, thin lips, right microtia with overfolded helix, small hands, micropenis (< P10), small testes and hallux valgus. His lymphocyte karyotype was mos 47,XY,+9[4]/46,XY[50]. Additional cytogenetic assessment of the skin showed normal results. The second patient was a two-year-old girl who was initially assessed at five months of age, when she presented weight of 5.3 kg (< P3), height of 61.5 cm (P2-P10), head circumference of 40.5 cm (P25), sparse hair, micrognathia, right ear with overfolded helix and preauricular pit, triphalangeal thumbs and sacral dimple. She also had a history of congenital heart disease, hearing loss, hypotonia, delayed neuropsychomotor development and swallowing disorder. Her lymphocyte karyotype was mos 47,XX,+9[3]/46,XX[69]. Both patients had unusual clinical findings (the first, hemifacial hypoplasia associated with microtia, with a phenotype of oculo-auriculo-vertebral spectrum, and the second, triphalangeal thumbs and hearing loss) and survival greater than what is usually described in the literature (< 1 year). Further reports will be critical for delineating the clinical features and determining the evolution of patients with mosaic trisomy 9.

Modeling abnormal early development with induced pluripotent stem cells from aneuploid syndromes

Many human diseases share a developmental origin that manifests during childhood or maturity. Aneuploid syndromes are caused by supernumerary or reduced number of chromosomes and represent an extreme example of developmental disease, as they have devastating consequences before and after birth. Investigating how alterations in gene dosage drive these conditions is relevant because it might help treat some clinical aspects. It may also provide explanations as to how quantitative differences in gene expression determine phenotypic diversity and disease susceptibility among natural populations. Here, we aimed to produce induced pluripotent stem cell (iPSC) lines that can be used to improve our understanding of aneuploid syndromes. We have generated iPSCs from monosomy X [Turner syndrome (TS)], trisomy 8 (Warkany syndrome 2), trisomy 13 (Patau syndrome) and partial trisomy 11;22 (Emanuel syndrome), using either skin fibroblasts from affected individuals or amniocytes from antenatal diagnostic tests. These cell lines stably maintain the karyotype of the donors and behave like embryonic stem cells in all tested assays. TS iPSCs were used for further studies including global gene expression analysis and tissue-specific directed differentiation. Multiple clones displayed lower levels of the pseudoautosomal genes ASMTL and PPP2R3B than the controls. Moreover, they could be transformed into neural-like, hepatocyte-like and heart-like cells, but displayed insufficient up-regulation of the pseudoautosomal placental gene CSF2RA during embryoid body formation. These data support that abnormal organogenesis and early lethality in TS are not caused by a tissue-specific differentiation blockade, but rather involves other abnormalities including impaired placentation.

Mosaic trisomy 9 at amniocentesis: prenatal diagnosis and molecular genetic analyses

OBJECTIVE

To present prenatal diagnosis and molecular genetic analyses of mosaic trisomy 9.

MATERIALS, METHODS AND RESULTS

A 35-year-old woman, gravida 3, para 1, underwent amniocentesis at 17 weeks of gestation because of her advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+9[3]/46,XX[6]. Repeat amniocentesis at 19 weeks of gestation revealed a karyotype of 47,XX,+9[6]/46,XX[19]. At 22 weeks of gestation, she was referred to a tertiary medical center for genetic counseling, and amniocentesis revealed a karyotype of 47,XX,+9[2]/46,XX[22]. Array comparative genomic hybridization analysis of uncultured amniocytes revealed no genomic imbalance in chromosome 9. However, interphase fluorescence in situ hybridization analysis of uncultured amniocytes showed that nine (18%) of 50 cells were trisomic for chromosome 9. Polymorphic DNA marker analyses also revealed a diallelic pattern with unequal biparental inheritance of chromosome 9 and a dosage ratio of 1:18 (paternal allele:maternal allele) in the uncultured amniocytes and a dosage ratio of 1:36 in the cultured amniocytes, indicating that the euploid cell line had maternal uniparental isodisomy for chromosome 9. Level II ultrasound demonstrated bilateral ventriculomegaly. The pregnancy was subsequently terminated, and a malformed fetus was delivered. Postnatal cytogenetic and polymorphic DNA marker analyses of the fetal and extraembryonic tissues confirmed the prenatal diagnosis.

CONCLUSION

Mosaic trisomy 9 carries a high risk of fetal abnormalities warranting detailed sonographic investigation of congenital malformations. Mosaic trisomy 9 can be associated with maternal uniparental disomy for chromosome 9 in euploid cell lines. Array comparative genomic hybridization is limited for the detection of low-level mosaicism.

Trisomy 9 mosaicism diagnosed in utero

We present three cases of trisomy 9 mosaicism diagnosed by amniocentesis with ongoing pregnancies after referral to our center due to fetal abnormalities. Two cases were associated with severe fetal growth restriction (FGR), each of which resulted in an intrauterine fetal demise (IUFD) in the third trimester. The other case involved mild FGR with a congenital diaphragmatic hernia and resulted in a live birth with severe development delay. A major prenatal finding of trisomy 9 mosaicism is FGR. Fetuses with trisomy 9 mosaicism can rarely survive in the case of severe FGR.

Antenatal detection of mosaic trisomy 9 by ultrasound: a case report and literature review

This paper presents a fetus with mosaic trisomy 9 diagnosed by chorionic villus sampling and confirmed by cordocentesis, and compares this case with published cases in order better to define the ultrasound markers confined to trisomy 9 syndrome. Detailed fetal ultrasound examination was carried out, revealing shortened femur, placental cysts and oligohydramnios. All published trisomy 9 cases with abnormal ultrasound findings were extracted from the MEDLINE database in the period from 1973 to 2002. We found 12 non-mosaic and 13 mosaic cases, including our case. The most frequent ultrasound abnormalities included characteristic cardiac, skeletal, craniofacial and central nervous system malformations. Intrauterine growth restriction and single umbilical artery were prevalent non-specific findings in both non-mosaic and mosaic groups. Parental chromosomal variations, as in our case, were not uncommon findings. When a fetus shows structural anomalies suggesting the presence of trisomy 9, karyotyping should be performed on both chorionic villi or amniocytes and fetal blood lymphocytes to enable a correct diagnosis to be made.

Phenotypical manifestations of partial trisomy 9 and monosomy 4 in two siblings

In this case report, we describe two siblings with a previously unreported partial monosomy 4q and partial trisomy 9q. The sibling karyotypes were determined to be 46,XX,der(4)t(4;9)(q33;q33)pat and 46,XY,der(4)t(4;9)-(q33;q33)pat. The siblings share several common pathological features, including VSD, PDA, low-set ears and digit anomalies as well as features consistent with Pierre-Robin syndrome and hydrocephalus. We review previously reported phenotypes associated with monosomy 4q and partial trisomy 9q and discuss potential mechanisms for these morphological insults with particular emphasis on neuropathology.

[Mosaic trisomy 9: report of a new case with a long-term survival]

INTRODUCTION

Trisomy 9 is an uncommon chromosome abnormality that may be seen in a mosaic or non-mosaic state.

OBJECTIVE

To better define the phenotype and prognosis of this disorder we report a new case of mosaic trisomy 9 with a long-term survival.

CLINICAL REPORT

We present the case of a female patient, born from the first pregnancy of a healthy couple. Fetal ultrasounds disclosed intrauterine growth retardation and oligohydramnios. Cesarean section was performed in the 34th week. Birth weight was 1,478 g. Neonatal examination showed: dolichocephaly; hypotelorism, microphthalmia, short palpebral fissures; broad-based nose with bulbous tip; micrognathia; low-set malformed ears; abnormal hands and feet; no other malformations. The initial karyotype determination was normal (46,XX). At 17 months of age, a second karyotype was requested because the patient developed severe psychomotor retardation. Chromosome analysis showed mosaic trisomy 9 (46,XX/47,XX, + 9). Six months later, a single upper central incisor was noted. To our knowledge, this feature has not been reported previously in the trisomy 9. The patient is now 4 years old. She shows severe psychomotor retardation, but no other complications.

COMMENTS

It is important to be aware of the possibility that mosaicism may exist in a patient with normal blood karyotype and abnormal phenotype. We conclude that a great number of cells is needed in order to obtain a correct karyotype diagnosis. Correct diagnosis is essential to define the prognosis and provide accurate genetic counselling.

Genetic syndromes and prenatally detected renal anomalies

Renal anomalies are frequently detected on the routine second trimester scan offered to all pregnant women in the UK. These anomalies may be isolated but can also be associated with other congenital anomalies. Many combinations of ultrasound scan findings constitute recognised genetic entities. Knowledge of these conditions is essential for adequate management of the pregnancy and subsequent balanced parental counselling. This short review discusses the common genetic syndromes associated with the renal abnormalities identified on the antenatal ultrasound scan, and also provides an overview of renal symptoms in chromosome imbalances and after teratogenic influences.

Prenatal diagnosis of trisomy 9

Fetal trisomy 9, especially its nonmosaic form, is a rare chromosomal abnormality and there are only 8 cases reported to have been sonographically detected in the prenatal period. We report a case of nonmosaic fetal trisomy 9, mimicking trisomy 13 on sonographic findings at 32 weeks' gestation. Although the incidence of trisomy 9 is rare, diagnosing trisomy 9 is important because the sonographic features are similar to those of trisomies 13 and 18, and cannot to be identified by routine fluorescencein situ hybridization. Because nonmosaic trisomy 9 is universally lethal, correct diagnosis and appropriate counseling is essential in patient care and clinical management.

Phenotypical variation in cousins with the identical partial trisomy 9 (pter-q22.2) and 7 (q35-qter) at 16 and 23 weeks gestation

From the study of numerical and structural chromosomal abnormalities, there is convincing evidence and accumulating information of a direct karyotype to phenotype correlation. Knowledge of phenotypic consequences of a specific chromosomal imbalance is important for genetic counseling and prenatal diagnosis. However, for unbalanced non-Robertsonian translocations a precise karyotype to phenotype correlation is difficult to predict for several reasons: (I) unbalanced non-Robertsonian translocations are rare, (II) the published case reports are often not age-matched, (III) varying breakpoints result in different lengths of the monosomic and trisomic segments and therefore the phenotype will depend on additional genes present or the loss of coding regions, and (IV) the combination of the same trisomy with different monosomies, or vice versa, can result in diverging phenotypes. Therefore, the study of the karyotype to phenotype correlation in affected relatives of the same age and the identical unbalanced translocation provides a good model to investigate phenotypic consequences of a specific genetic imbalance. We report of two second trimester fetuses with the identical major partial trisomy 9 (9pter-9q22.2) and minor partial trisomy 7 (q35-qter) resulting from a familial translocation (7;9)(q35;q22.2)mat. One fetus presented with a Dandy-Walker malformation, polymicrogyria, and mild dysmorphic features, whereas the other fetus showed unilateral cleft lip and palate without cerebral anomalies. Potential mechanisms for this different phenotypic expression of the same unbalanced translocation resulting in partial trisomy 9 and 7 in the two cousins and possible consequences for genetic counseling and prenatal diagnosis are discussed.

Prenatal ultrasound findings in complete trisomy 9

OBJECTIVE

To report on the prenatal ultrasound findings associated with complete trisomy 9.

METHODS

Cases of complete trisomy 9 diagnosed prenatally were identified by reviewing the reports from two large cytogenetics laboratories serving tertiary referral centers for prenatal diagnosis. Information on prenatal ultrasound findings and outcome was obtained in all cases.

RESULTS

Nine cases of complete trisomy 9 were identified. The diagnosis was made in the first trimester in four cases, in the second trimester in three and in the third trimester in two. Two fetuses underwent first-trimester ultrasound screening for aneuploidy and the nuchal translucency thickness was increased in both. All five fetuses detected in the second and third trimesters had several fetal anomalies including Dandy-Walker malformation in four cases, facial dysmorphism in four, genitourinary anomalies in three, congenital heart defects in three, ventriculomegaly in three, abnormal hands in two and megacisterna magna in one. Four fetuses were growth-restricted at the time of ultrasound evaluation. However, the two cases diagnosed in the third trimester had routine second-trimester anomaly scans reported as normal. There were no survivors in this series.

CONCLUSION

Fetuses with complete trisomy 9 have multiple anomalies that can be readily detected prenatally by ultrasound. These mainly include, but are not restricted to, craniofacial, cardiovascular, musculoskeletal and genitourinary malformations. However, findings can be subtle and therefore missed at the routine second-trimester scan.

Mosaic trisomy 9 and lobar holoprosencephaly

The main features of trisomy 9 syndrome in mosaic and non-mosaic forms have been thoroughly described. Characteristic traits are low-set malformed ears, micrognathia, broad nose with bulbous tip, abnormal brain, congenital heart defects, abnormal hands and feet, genital abnormalities, and early death. We report a case of mosaic trisomy 9 with holoprosencephaly (HPE). The propositi was born at 37 weeks, with intra-uterine growth retardation, hypotelorism and single nostril, ventricular septal defect, anterior placement of anus, clenched hands with thumb adduction and ulnar deviation. Facial anomalies characteristic of trisomy 9 included deeply set eyes and short palpebral fissures, flat face with maxillary hypoplasia, small mouth, and low-set posteriorly angulated ears. Cytogenetic analysis showed mosaic trisomy 9 with 17% trisomic cells. Pathology confirmed lobar HPE. In literature, isolated arrhinia, related to the HPE spectrum, was reported in one case of mosaic trisomy 9. Our case raises the question of the causative role of trisomy 9 in full blown HPE.

Low incidence of UPD in spontaneous abortions beyond the 5th gestational week

Approximately 15-20% of all clinically recognised pregnancies abort, most commonly between 8-12 gestational weeks. While the majority of early pregnancy losses is attributed to cytogenetic abnormalities, the aetiology of approximately 40% of early abortions remains unclear. To determine additional factors causing spontaneous abortions we retrospectively searched for uniparental disomies (UPD) in 77 cytogenetically normal diploid spontaneous abortions. In all cases an unbalanced chromosome anomaly was ruled out by cytogenetic investigation of chorionic/amniotic membranes and/or chorionic villi. For UPD screening microsatellite analyses were performed on DNA of abortion specimens and parental blood using highly polymorphic markers showing UPD in two cases. The distribution of markers analysed indicated maternal heterodisomy for chromosome 9 (UPhD(9)mat) in case 1 and paternal isodisomy for chromosome 21 (UPiD(21)pat) in case 2. The originating mechanism suggested was monosomy complementation in UPiD(21)pat and trisomy rescue in UPhD(9)mat. In the case of UPhD(9)mat purulent chorioamnionitis was noted and a distinctly growth retarded embryo of 3 cm crown-rump length showing no gross external malformations. Histological analysis in the case of UPiD(21)pat suggested a primary anlage defect. Our results indicate that less than 3% of genetically unexplained pregnancy wastage is associated with total chromosome UPD. UPD may contribute to anlage defects of human conception. Chromosome aneuploidy correction can occur in very early cleavage stages. More research, however, ought to be performed into placental mosaicism to further clarify timing and mechanisms involved in foetal UPD.

A case of maternal uniparental disomy of chromosome 9 diagnosed prenatally and the related problem of residual trisomy

Non-mosaic trisomy 9 was found in a chorionic villus (CV) sample taken from a 43-year-old woman referred for prenatal chromosome analysis due to advanced maternal age. Follow-up amniocentesis revealed level 2 mosaicism for trisomy 9. Trisomy 9 was not detected at fetal blood sampling. Molecular analysis of fetal (amniocyte) DNA showed maternal uniparental heterodisomy (UPD) for chromosome 9. Two crossovers resulted in a region of isodisomy in the distal long arm. Trisomy rescue of a meiosis 1 segregation error seems to have been responsible for the uniparental disomy of chromosome 9. The pregnancy continued and neonatal blood testing showed a mosaic trisomy 9 karyotype, i.e. 4/50 cells analysed. Clinical postnatal follow-up for a period of 1 year has documented only minor facial dysmorphism and skeletal abnormalities. Development appears unremarkable. This case is the second report of maternal uniparental disomy for chromosome 9 detected prenatally and is the first case followed up post-term. This report highlights the difficulty of making informed prognostic assessments in such cases despite extensive laboratory investigation.

Rare trisomy mosaicism diagnosed in amniocytes, involving an autosome other than chromosomes 13, 18, 20, and 21: karyotype/phenotype correlations

In order to determine the significance of trisomy mosaicism of an autosome other than chromosomes 13, 18, 20, and 21, 151 such cases diagnosed prenatally through amniocentesis were reviewed. These rare trisomy mosaicism cases include 54 from 17 cytogenetic laboratories, 34 from a previous North American mosaicism survey, and 63 from published reports. All were cases of true mosaicism with information available on pregnancy outcome, and with no evidence of biased ascertainment. There were 11 cases of 46/47, +2; 2 of 46/47, +3; 2 of 46/47, +4; 5 of 46/47, +5; 3 of 46/47, +6; 8 of 46/47, +7; 14 of 46/47, +8; 25 of 46/47, +9; 2 of 46/47, +11; 23 of 46/47, +12; 5 of 46/47, +14; 11 of 46/47, +15; 21 of 46/47, +16; 7 of 46/47, +17; 1 of 46/47, +19; and 11 of 46/47, +22. As to the risk of an abnormal outcome, the data showed a very high risk (> 60 per cent) for 46/47, +2, 46/47, +16, and 46/47, +22; a high risk (40-59 per cent) for 46/47, +5, 46/47, +9, 46/47, +14, and 46/47, +15; a moderately high risk (20-39 per cent) for 46/47, +12; a moderate risk (up to 19 per cent) for 46/47, +7 and 46/47, +7 and 46/47, +8; a low risk for 46/47, +17; and an undetermined risk, due to lack of cases, for the remaining autosomal trisomy mosaics. Most cases were evaluated at birth or at termination, so subtle abnormalities may have escaped detection and developmental retardation was not evaluated at all. Comparison of the phenotypes of prenatally diagnosed abnormal cases and postnatally diagnosed cases with the same diagnosis showed considerable concordance. Since the majority of anomalies noted are prenatally detectable with ultrasound, an ultrasound examination should be performed in all prenatally diagnosed cases. In cytogenetic confirmation studies, the data showed much higher confirmation rates in cases with abnormal outcomes than in cases with normal outcomes [81 per cent vs. 55 per cent for fibroblasts (from skin, fetal tissue, and/or cord); 88 per cent vs. 46 per cent for placental cells; 22 per cent vs. 10 per cent for blood cells]. The confirmation rate reached 85 per cent when both fibroblasts and placental tissues were studied in the same case (with trisomic cells found in one or the other, or both). Therefore, one must emphasize that both fibroblasts and placental tissues should be studied. Except for 46/47, +8 and 46/47, +9, PUBS is of limited value for prenatal diagnosis of rate trisomy mosaicism. DNA studies for UPD are suggested for certain chromosomes with established imprinting effects, such as chromosomes 7, 11, 14, and 15, and perhaps for chromosomes 2 and 16, where imprinting effects are likely.

Mosaic vs. nonmosaic trisomy 9: report of a liveborn infant evaluated by fluorescence in situ hybridization and review of the literature

We report on a newborn infant with multiple congenital anomalies and apparent nonmosaic trisomy 9 in the blood (by conventional cytogenetic studies) who died shortly after birth. Clinical observations at birth and autopsy are compared with phenotypes of mosaic and nonmosaic trisomy 9 cases reported previously. Unlike the initial cytogenetic analysis, fluorescence in situ hybridization (FISH) studies of metaphase and interphase blood cells and skin fibroblasts detected the presence of euploid and trisomy 9 cells. These results suggest that earlier reports of trisomy 9, which relied on conventional chromosome analysis of a few metaphase cells and/or only one tissue type, may not have excluded mosaicism, and that trisomy 9 may be viable only in the mosaic state.