Trisomy 12 mosaicism confirmed in multiple organs from a liveborn child

Challenging diagnoses of tetraploidy/diploidy and trisomy 12: utility of first-tier prenatal testing methods

Introduction: Chromosome mosaicism and low-grade mosaicism present a challenge for diagnosis in the era of SNP array and NGS. Tetraploidy is a rare numerical chromosomal abnormality characterized by the presence of four copies of each chromosome. The prevalence of tetraploidy/diploidy mosaicism cases is extremely rare in the human population. Accurate estimates of the frequency of this chromosomal anomaly are lacking due to its classification as an extremely rare and difficult-to-detect condition. Methods: In this report, we describe two cases involving challenging diagnoses of tetraploidy/diploidy and trisomy 12. We utilized advanced genetic testing techniques, including SNP array, to examine the chromosomal abnormalities in these cases. We compared the results from SNP array to conventional G band karyotyping to assess the utility of first-tier prenatal testing methods. Results:Our analysis revealed two cases of tetraploidy/diploidy and trisomy 12 with atypical presentations. SNP array analysis provided higher resolution and more precise information about the chromosomal anomalies in these cases compared to conventional G band karyotyping. Additionally, the prevalence of tetraploidy/diploidy mosaicism was confirmed to be extremely rare in the population. Discussion: Low-level mosaicism is difficult to diagnose, and in many cases, it has traditionally been identified through techniques such as G band karyotype or FISH. Microarray has become an invaluable diagnostic tool for detecting chromosomal abnormalities, offering high-resolution insights. However, it may not always be able to detect rare occurrences of tetraploidy or tetraploidy/diploidy mosaicism. As a result, it is recommended to perform a G band karyotype analysis after obtaining a negative microarray result before considering other diagnostic methods with a potentially higher yield of diagnosis. For the detection of low-level mosaicism, combined diagnostic methods should be considered. The diagnosis of mosaicism is a multistep process that can be time-consuming, often requiring the application of more than one diagnostic technique. This approach is crucial for accurate diagnosis and comprehensive patient care. Further research is warranted to better understand the underlying mechanisms of these rare chromosomal anomalies and to develop more effective diagnostic strategies for challenging cases.

Pigmentary mosaicism as a recurrent clinical manifestation in three new patients with mosaic trisomy 12 diagnosed postnatally: cases report and literature review

Background

To date, only twenty-one cases diagnosed postnatally with mosaic trisomy 12 have been reported. The most frequent phenotypic manifestations are developmental delay, dysmorphic facial features, congenital heart defects, digital alterations, and pigmentary disorders. In the present report, detailed clinical and genetic profiles of three unrelated new patients with mosaic trisomy 12 are described and compared with previously reported cases.

Case presentation

In the present report, we include the clinical, cytogenetic, and molecular description of three Mexican patients diagnosed postnatally with mosaic trisomy 12. At phenotypic level, the three patients present with developmental delay, dysmorphic facial features, congenital heart defects and skin pigmentary anomalies. Particularly, patient 1 showed unique eye alterations as bilateral distichiasis, triple rows of upper lashes, and digital abnormalities. In patient 2 redundant skin, severe hearing loss, and hypotonia were observed, and patient 3 presented with hypertelorism and telecanthus. Hyperpigmentation with disseminated pigmentary anomalies is a common trait in all of them. The cytogenetic study was carried out under the strict criteria of analysis, screening 50–100 metaphases from three different tissues, showing trisomy 12 mosaicism in at least one of the three different tissues analyzed. With SNParray, the presence of low-level mosaic copy number variants not previously detected by cytogenetics, and uniparental disomy of chromosome 12, was excluded. STR markers allowed to confirm the absence of uniparental disomy as well as to know the parental origin of supernumerary chromosome 12.

Conclusions

The detailed clinical, cytogenetic, and molecular description of these three new patients, contributes with relevant information to delineate more accurately a group of patients that show a heterogeneous phenotype, although sharing the same chromosomal alteration. The possibility of detecting mosaic trisomy 12 is directly associated with the sensitivity of the methodology applied to reveal the low-level chromosomal mosaicism, as well as with the possibility to perform the analysis in a suitable tissue.

Prenatal diagnosis of mosaicism for trisomy 12 in a single colony at amniocentesis in a pregnancy with a favorable outcome

OBJECTIVE

We present prenatal diagnosis of mosaicism for trisomy 12 in a single colony at amniocentesis with a favorable outcome.

CASE REPORT

A 36-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+12[1]/46,XY[14]. In 15 colonies of cultured amniocytes, all three cells in one colony had the karyotype of 47,XY,+12, while the rest 14 colonies had the karyotype of 46,XY. The parental karyotypes were normal. Prenatal ultrasound findings were unremarkable. Polymorphic DNA marker analysis using the DNAs extracted from cultured amniocytes and parental bloods excluded uniparental disomy (UPD) 12. At 37 weeks of gestation, a healthy 2,828-g male baby was delivered with no phenotypic abnormality. The cord blood had a karyotype of 46,XY in 40/40 lymphocytes. Postnatal interphase fluorescence in situ hybridization (FISH) analysis on buccal cells and urinary cells revealed normal signals in 72/72 buccal cells, and trisomy 12 signals in 1/47 (2.1%) urinary cells compared with 0% (0/75 cells) of trisomy 12 signals in the normal control.

CONCLUSION

Mosaicism for trisomy 12 in a single colony at amniocentesis without UPD 12 and fetal ultrasound abnormalities can be associated with a favorable outcome.

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.

Prenatal diagnosis of mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis in a pregnancy with a favorable outcome

OBJECTIVE

We present prenatal diagnosis of mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis with a favorable outcome.

CASE REPORT

A 23-year-old woman underwent amniocentesis at 24 weeks of gestation because of congenital bowel dilation in the fetus. Amniocentesis revealed a karyotype of 48,XX,+11,+12[1]/46,XX[24]. In 25 colonies of cultured amniocytes, all five cells in one colony had the karyotype of 48,XX,+11,+12, while the rest 24 colonies had the karyotype of 46,XX. The parental karyotypes were normal. Repeat amniocentesis was performed at 26 weeks of gestation. Interphase fluorescence in situ hybridization (FISH), array comparative genomic hybridization (aCGH) and quantitative fluorescent polymerase chain reaction (QF-PCR) were applied on the uncultured amniocytes, and conventional cytogenetic analysis was applied on cultured amniocytes. Interphase FISH analysis showed no trisomy 11 signal and no trisomy 12 signal in 102 uncultured amniocytes. QF-PCR analysis excluded uniparental disomy (UPD) 11 and UPD 12. aCGH analysis showed no genomic imbalance. The cultured amniocytes at repeat amniocentesis had the karyotype of 46,XX in 13/13 colonies. At term, a healthy 3445-g female baby was delivered with no phenotypic abnormality except imperforate anus and a perianal fistula. The cord blood had a karyotype of 46,XX in 40/40 lymphocytes. Postnatal interphase FISH analysis of buccal cells and urinary cells revealed trisomies 11 and 12 signals in 11/111 (9.9%) buccal cells compared with 3% in normal control, and in 3/103 (2.9%) urinary cells compared with 0.98% in normal control.

CONCLUSION

Mosaicism for double trisomies of trisomy 11 and trisomy 12 in a single colony at amniocentesis without UPD 11 and UPD 12 can be associated with a favorable outcome.

Four children with postnatally diagnosed mosaic trisomy 12: Clinical features, literature review, and current diagnostic capabilities of genetic testing

Children or adults with mosaic trisomy 12 diagnosed postnatally are extremely rare. Only a small number of patients with this mosaicism have been reported in the literature. The clinical manifestation of mosaic trisomy 12 is variable, ranging from mild developmental delay to severe congenital anomaly and neonatal death. The trisomy 12 cells are not usually able to be detected by phytohemagglutinin stimulated peripheral blood chromosome analysis. The variability of phenotypes and the limited number of patients with this anomaly pose a challenge to predict the clinical outcomes. In this study, we present the phenotypes and laboratory findings in four patients and review the 11 previously reported patients with mosaic trisomy 12 diagnosed postnatally, as well as 11 patients with mosaic trisomy 12 diagnosed prenatally. The findings of this study provide useful information for laboratory diagnosis and clinical management of these patients.

Harmonizing Clinical Sequencing and Interpretation for the eMERGE III Network

The advancement of precision medicine requires new methods to coordinate and deliver genetic data from heterogeneous sources to physicians and patients. The eMERGE III Network enrolled >25,000 participants from biobank and prospective cohorts of predominantly healthy individuals for clinical genetic testing to determine clinically actionable findings. The network developed protocols linking together the 11 participant collection sites and 2 clinical genetic testing laboratories. DNA capture panels targeting 109 genes were used for testing of DNA and sample collection, data generation, interpretation, reporting, delivery, and storage were each harmonized. A compliant and secure network enabled ongoing review and reconciliation of clinical interpretations, while maintaining communication and data sharing between clinicians and investigators. A total of 202 individuals had positive diagnostic findings relevant to the indication for testing and 1,294 had additional/secondary findings of medical significance deemed to be returnable, establishing data return rates for other testing endeavors. This study accomplished integration of structured genomic results into multiple electronic health record (EHR) systems, setting the stage for clinical decision support to enable genomic medicine. Further, the established processes enable different sequencing sites to harmonize technical and interpretive aspects of sequencing tests, a critical achievement toward global standardization of genomic testing. The eMERGE protocols and tools are available for widespread dissemination.

Mosaic Trisomy 12 Associated with Overgrowth Detected in Fibroblast Cell Lines

Mosaic trisomy 12 is a rare anomaly, and only 9 cases of live births with this condition have been reported in the literature. The clinical phenotype is variable, including neuropsychomotor developmental delay, congenital heart disease, microcephaly, cutaneous spots, facial asymmetry, prominent ears, hypotonia, retinopathy, and sensorineural hearing loss. A 2-year-old female presented with neuropsychomotor developmental delay, prominent forehead, dolichocephaly, patchy skin pigmentation, and unexpected overgrowth at birth. Cytogenetic analysis of her peripheral blood showed normal results, suggesting the presence of a chromosomal alteration in other tissues. Further studies using G-banding and FISH performed on fibroblasts from both hyper- and hypopigmented regions identified a 47,XX,+12/46,XX karyotype. To the best of our knowledge, no patients with mosaic trisomy 12 associated with overgrowth have been reported to date. Congenital overgrowth and neonatal overgrowth have been frequently linked to Pallister-Killian syndrome (PKS; OMIM 601803). This case suggests the possibility of an association of genes present in the 12p region with fetal overgrowth, considering that chromosomal duplications could lead to an increase in the production of aberrant transcripts and disturbing gene dosage effects. This case highlights the importance of cytogenetic analysis in different tissues to provide relevant information to the specific genotype/phenotype correlation.

Anatomy of trisomy 12

Trisomy 12 is a rare aneuploidy and fetuses with this defect tend to spontaneously abort. However, mosaicism allows this anomaly to manifest itself in live births. Due to the fact that mosaicism represents a common genetic abnormality, trisomy 12 is encountered more frequently than expected at a rate of 1 in 500 live births. Thus, it is imperative that medical practitioners are aware of this aneuploidy. Moreover, this genetic disorder may result from a complete or partial duplication of chromosome 12. A partial duplication may refer to a specific segment on the chromosome, or one of the arms. On the other hand, a complete duplication refers to duplication of both arms of chromosome 12. The combination of mosaicism and the variable duplication sites has led to variable phenotypes ranging from normal phenotype to Potter sequence to gross physical defects of the various organ systems. This article provides a review of the common anatomical variation of the different types of trisomy 12. This review revealed that further documentation is needed for trisomy 12q and complete trisomy 12 to clearly delineate the constellation of anomalies that characterize each genetic defect. Clin. Anat. 29:633-637, 2016. © 2016 Wiley Periodicals, Inc.

Constitutional and acquired autosomal aneuploidy

Chromosomal imbalances can result from numerical or structural anomalies. Numerical chromosomal abnormalities are often referred to as aneuploid conditions. This article focuses on the occurrence of constitutional and acquired autosomal aneuploidy in humans. Topics covered include frequency, mosaicism, phenotypic findings, and etiology. The article concludes with a consideration of anticipated advances that might allow for the development of screening tests and/or lead to improvements in our understanding and management of the role that aneuploidy plays in the aging process and acquisition of age-related and constitutional conditions.

Transient myeloproliferative disorder with trisomy 12

The authors report the first case of transient myeloproliferative disorder (TMD) in a neonate with trisomy 12. The clinical course consisted of respiratory distress since birth with probability of transient tachypnea of newborn, but routine investigation revealed total leukocyte count of 56000/microL with 91% blasts, which returned to normal spontaneously during the subsequent 3 weeks. GTG-banded karyotype from peripheral blood was done to detect any mutation, specifically trisomy 21, but the proband revealed trisomy 12 and denaturing polyacrylamide gel electrophoresis (PAGE) detected mutation in exon 2 of GATA1. The condition has been described in association with Down syndrome (trisomy 21) but never with trisomy 12. This case demonstrates the importance of knowing this entity so that it is not erroneously diagnosed as a leukemic process. This is extremely important because most cases of TMD resolve spontaneously within a few weeks to months and do not require treatment other than supportive measures. A search of the literature did not reveal any similar case.

A Rapid and Noninvasive Method for Detecting Tissue-Limited Mosaicism: Detection of i(12)(p10) in Buccal Smear from a Child with Pallister-Killian Syndrome

Pallister-Killian syndrome (PKS), a rare disorder, is characterized by tissue-limited or tissue-specific mosaicism. The characteristic chromosome abnormality associated with PKS is i(12p), which is seen predominantly in skin fibroblast cultures. Diagnosis of i(12p) has been carried out on buccal smears before and was shown to be an easy and feasible method. All previously published studies used alpha-satellite probes for the diagnosis and as such have several pitfalls. Our approach, using dual-color, locus-specific probes, has high specificity and sensitivity for the diagnosis of i(12p). Using statistical analysis, we have also confirmed that the signal pattern in interphase nuclei is consistent with isochromosome 12p.