Trisomy 7 mosaicism prenatally misdiagnosed and maternal uniparental disomy in a child with pigmentary mosaicism and Russell- Silver syndrome

Prenatal diagnosis of a trisomy 7 mosaic case: CMA, CNV-seq, karyotyping, interphase FISH, and MS-MLPA, which technique to choose?

OBJECTIVE

This study aims to perform a prenatal genetic diagnosis of a high-risk fetus with trisomy 7 identified by noninvasive prenatal testing (NIPT) and to evaluate the efficacy of different genetic testing techniques for prenatal diagnosis of trisomy mosaicism.

METHODS

For prenatal diagnosis of a pregnant woman with a high risk of trisomy 7 suggested by NIPT, karyotyping and chromosomal microarray analysis (CMA) were performed on an amniotic fluid sample. Low-depth whole-genome copy number variation sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) were used to clarify the results further. In addition, methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) was performed to analyze the possibility of uniparental disomy(UPD).

RESULTS

Amniotic fluid karyotype analysis revealed a 46, XX result. Approximately 20% mosaic trisomy 7 was detected according to the CMA result. About 16% and 4% of mosaicism was detected by CNV-seq and FISH, respectively. MS-MLPA showed no methylation abnormalities. The fetal ultrasound did not show any detectable abnormalities except for mild intrauterine growth retardation seen at 39 weeks of gestation. After receiving genetic counseling, the expectant mother decided to continue the pregnancy, and follow-up within three months of delivery was normal.

CONCLUSION

In high-risk NIPT diagnosis, a combination of cytogenetic and molecular genetic techniques proves fruitful in detecting low-level mosaicism. Furthermore, the exclusion of UPD on chromosome 7 remains crucial when NIPT indicates a positive prenatal diagnosis of trisomy 7.

Pregnancy outcome of confined placental mosaicism: meta-analysis of cohort studies

OBJECTIVE

This study aimed to assess the rate of adverse obstetrical and neonatal outcomes in pregnancies diagnosed with confined placental mosaicism relative to that of unaffected controls.

DATA SOURCES

Web-based databases were searched using relevant key words, and articles published from 1980 to February 2022 were retrieved.

STUDY ELIGIBILITY CRITERIA

Observational studies in English language including ≥10 cases of singleton pregnancies with diagnosis of confined placental mosaicism were included. The diagnosis was established after detection of any chromosomal abnormality at chorionic villus sampling for any indication, followed by normal karyotype from amniotic fluid or neonatal leukocyte culture.

METHODS

Two authors independently screened the references for eligibility, data extraction, and assessment of methodological quality using the Newcastle-Ottawa scale. All available obstetrical and neonatal outcomes were recorded. Random-effect meta-analysis was performed to estimate pooled odds ratios and 95% confidence intervals of available outcomes in pregnancies with and without confined placental mosaicism. Statistical heterogeneity was evaluated with I2 statistics (International Prospective Register of Systematic Reviews registration number: CRD42021260319).

RESULTS

Of the 80 articles reviewed, 8 retrospective matched-cohort studies (708 cases of confined placental mosaicism and 11,599 unaffected controls) compared cases with and without confined placental mosaicism and were included in the meta-analysis. The risk of delivering small-for-gestational-age neonates was significantly increased in confined placental mosaicism pregnancies according to crude analysis (odds ratio, 2.45; 95% confidence interval, 1.23-4.89; I2=72%) and to sensitivity analysis of high-quality studies (odds ratio, 3.65; 95% confidence interval, 2.43-5.57; I2=0%). Similarly, confined placental mosaicism resulted in an increased risk of birthweight below the third centile (odds ratio, 5.33; 95% confidence interval, 1.19-24.19; I2= 83%). Subgroup analysis revealed that the risk of delivering small-for-gestational-age neonates was 3-fold higher for confined placental mosaicism excluding trisomy 16, and 11-fold higher for cases including trisomy 16 only vs unaffected controls, respectively. No difference was found in the risk of low birthweight and preterm birth (at <37 weeks' gestation). Other outcomes were insufficiently reported, therefore they were not analyzed.

CONCLUSION

Pregnant women prenatally diagnosed with confined placental mosaicism have an increased risk of impaired fetal growth, suggesting the need for intensified antenatal surveillance.

Prenatal diagnosis of mosaicism for double aneuploidy of 47,XXY and trisomy 7 (48,XXY,+7) at amniocentesis in a pregnancy with a favorable outcome

OBJECTIVE

We present prenatal diagnosis of mosaicism for double aneuploidy of 47, XXY and trisomy 7 (48,XXY,+7) at amniocentesis in a pregnancy with a favorable outcome.

CASE REPORT

A 33-year-old woman underwent amniocentesis at 17 weeks of gestation because of an increased risk for Down syndrome in maternal serum screening. Amniocentesis revealed a karyotype of 48,XXY,+7[8]/46,XY[16]. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes revealed the result of arr [GRCh37] (7) × 3 [0.54], (X) × 2 [0.52], (Y) × 1, compatible with trisomy 7 mosaicism and Klinefelter syndrome mosaicism. The parental karyotypes and prenatal ultrasound findings were normal. Repeat amniocentesis performed at 23 weeks of gestation revealed a karyotype of 48,XXY,+7[13]/46,XY[7]. Simultaneous molecular cytogenetic analyses on uncultured amniocytes revealed 30% mosaicism for 48,XXY,+7 by aCGH and 37% (37/100 cells) mosaicism for trisomy 7 and disomy X by interphase fluorescence in situ hybridization (FISH) analysis. Polymorphic DNA marker analysis excluded uniparental disomy (UPD) 7 and indicated a maternal origin of the chromosome aberration. The pregnancy was continued to 39 weeks of gestation, and a 3070-g healthy male baby was delivered. The cord blood had a karyotype of 46,XY, the umbilical cord had a karyotype of 48,XXY,+7[3]/46,XY[37], and the placenta had a karyotype of 48,XXY,+7. At age one month, the neonate was phenotypically normal, and interphase FISH analysis revealed 4.8% (5/105 cells) mosaicism on buccal mucosal cells and 8.9% (8/90 cells) mosaicism on urinary cells for trisomy 7 and disomy X, compared with 2% in normal control. Interphase FISH analysis on buccal mucosal cells at age two months revealed normal findings in 100/100 cells.

CONCLUSION

Mosaic 48,XXY,+7 at amniocentesis without UPD 7 can be associated with a favorable fetal outcome. Cytogenetic discrepancy between cultured amniocytes and uncultured amniocytes may occur in mosaic 48,XXY,+7 at amniocentesis.

Ontogenetic and Pathogenetic Views on Somatic Chromosomal Mosaicism

Intercellular karyotypic variability has been a focus of genetic research for more than 50 years. It has been repeatedly shown that chromosome heterogeneity manifesting as chromosomal mosaicism is associated with a variety of human diseases. Due to the ability of changing dynamically throughout the ontogeny, chromosomal mosaicism may mediate genome/chromosome instability and intercellular diversity in health and disease in a bottleneck fashion. However, the ubiquity of negligibly small populations of cells with abnormal karyotypes results in difficulties of the interpretation and detection, which may be nonetheless solved by post-genomic cytogenomic technologies. In the post-genomic era, it has become possible to uncover molecular and cellular pathways to genome/chromosome instability (chromosomal mosaicism or heterogeneity) using advanced whole-genome scanning technologies and bioinformatic tools. Furthermore, the opportunities to determine the effect of chromosomal abnormalities on the cellular phenotype seem to be useful for uncovering the intrinsic consequences of chromosomal mosaicism. Accordingly, a post-genomic review of chromosomal mosaicism in the ontogenetic and pathogenetic contexts appears to be required. Here, we review chromosomal mosaicism in its widest sense and discuss further directions of cyto(post)genomic research dedicated to chromosomal heterogeneity.

Pigmentary mosaicism: a review of original literature and recommendations for future handling

Background

Pigmentary mosaicism is a term that describes varied patterns of pigmentation in the skin caused by genetic heterogeneity of the skin cells. In a substantial number of cases, pigmentary mosaicism is observed alongside extracutaneous abnormalities typically involving the central nervous system and the musculoskeletal system. We have compiled information on previous cases of pigmentary mosaicism aiming to optimize the handling of patients with this condition. Our study is based on a database search in PubMed containing papers written in English, published between January 1985 and April 2017. The search yielded 174 relevant and original articles, detailing a total number of 651 patients.

Results

Forty-three percent of the patients exhibited hyperpigmentation, 50% exhibited hypopigmentation, and 7% exhibited a combination of hyperpigmentation and hypopigmentation. Fifty-six percent exhibited extracutaneous manifestations. The presence of extracutaneous manifestations in each subgroup varied: 32% in patients with hyperpigmentation, 73% in patients with hypopigmentation, and 83% in patients with combined hyperpigmentation and hypopigmentation. Cytogenetic analyses were performed in 40% of the patients: peripheral blood lymphocytes were analysed in 48%, skin fibroblasts in 5%, and both analyses were performed in 40%. In the remaining 7% the analysed cell type was not specified. Forty-two percent of the tested patients exhibited an abnormal karyotype; 84% of those presented a mosaic state and 16% presented a non-mosaic structural or numerical abnormality. In patients with extracutaneous manifestations, 43% of the cytogenetically tested patients exhibited an abnormal karyotype. In patients without extracutaneous manifestations, 32% of the cytogenetically tested patients exhibited an abnormal karyotype.

Conclusion

We recommend a uniform parlance when describing the clinical picture of pigmentary mosaicism. Based on the results found in this review, we recommend that patients with pigmentary mosaicism undergo physical examination, highlighting with Wood’s light, and karyotyping from peripheral blood lymphocytes and skin fibroblasts. It is important that both patients with and without extracutaneous manifestations are tested cytogenetically, as the frequency of abnormal karyotype in the two groups seems comparable. According to the results only a minor part of patients, especially those without extracutaneous manifestations, are tested today reflecting a need for change in clinical practice.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0778-6) contains supplementary material, which is available to authorized users.

Formation of upd(7)mat by trisomic rescue: SNP array typing provides new insights in chromosomal nondisjunction

Background

Maternal uniparental disomy (UPD) of chromosome 7 (upd(7)mat) accounts for approximately 10% of patients with Silver-Russell syndrome (SRS). For upd(7)mat and trisomy 7, a significant number of mechanisms have been proposed to explain the postzygotic formation of these chromosomal compositions, but all have been based on as small number of cases. To obtain the ratio of isodisomy and heterodisomy in UPDs (hUPD, iUPD) and to determine the underlying formation mechanisms, we analysed a large cohort of upd(7)mat patients (n = 73) by SNP array typing. Based on these data, we discuss the UPDs and their underlying trisomy 7 formation mechanisms.

Results

A whole chromosome 7 maternal iUPD was confirmed in 28.8%, a mixture or complete maternal hUPD in 71.2% of patients.

Conclusions

We could demonstrate that nondisjunction mechanism affecting chromosome 7 are similar to that of the chromosomes more frequently involved in trisomy (and/or UPD), and that mechanisms other than trisomic rescue have a lower significance than previously suspected. Furthermore, we suggest SNP array typing for future parent- and cell-stage-of origin studies in human aneuploidies as they allow the definite classification of trisomies and UPDs, and provide information on recombinational events and their suggested association with aneuploidy formation.

Do you know this syndrome? Dyspigmentation along the Blaschko lines caused by trisomy 7 mosaicism

Dyspigmentation along the Blaschko lines is strongly suggestive of a mosaic skin disorder. We report a 9-year-old male patient who presented with swirls and streaks of both hypo and hyperpigmentation involving the entire body. Additionally, he had hypertrichosis, musculoskeletal and minor neurodevelopment abnormalities but no intellectual disability. Cultured fibroblast displayed trisomy 7 mosaicism, which can explain this pigmentary phenotype. Widespread dyspigmentation associated with involvement of other organs should prompt systemic examination to detect additional anomalies and genetic evaluation should be considered, even with normal fetal karyotype.

Examinations of maternal uniparental disomy and epimutations for chromosomes 6, 14, 16 and 20 in Silver-Russell syndrome-like phenotypes

Background

Silver-Russell syndrome (SRS) is a growth retardation disorder with a very broad molecular and clinical spectrum. Whereas the association of SRS with imprinting disturbances of chromosomes 11p15.5 and 7 is generally accepted, there are controversial discussions on the involvement of other molecular changes. The recent reports on the occurrence of maternal uniparental disomies of chromosomes 6, 16 and 20 (upd(6, 16, 20)mat), as well as 14q32 imprint alterations in patients with SRS phenotypes raise the question on the involvement of these mutations in the etiology of SRS.

Methods

A cohort of 54 growth retarded patients with SRS features was screened for aberrant methylation patterns of chromsomes 6, 14, 16 and 20.

Results

One carrier of a 14q32 epimutation was identified whereas epimutations and maternal UPD for chromosomes 6, 16 and 20 were excluded.

Conclusions

Our data and those from the literature confirm that 14q32 disturbances significantly contribute to the mutation spectrum in this cohort. Furthermore, maternal uniparental disomy of chromosomes 6, 16 and 20 can be observed, but are rare. In case they occur they can be regarded as causative for clinical features.

Neonatal Silver-Russell syndrome with maternal uniparental heterodisomy, trisomy 7 mosaicism, and dysplasia of the cerebellum

OBJECTIVES

We report here the unusual association of Silver-Russell syndrome (SRS) and cerebellar dysplasia with trisomy 7 mosaicism and maternal uniparental disomy of chromosome 7 [UPD(7)m].

METHODS

Low-level trisomy 7 mosaicism was diagnosed prenatally on amniocytes, and UPD(7)m was confirmed after birth.

RESULTS

Medical examination at birth showed dysmorphic facial features of SRS. Cytogenetic analysis on several tissues and cells confirmed mosaic trisomy 7. Unusual severe psychomotor retardation, hypotonia, and choreoathetoid movement were noted at 6 months. Brain magnetic resonance imaging showed both cerebellar hypoplasia and dysplasia.

CONCLUSIONS

This unusual association of SRS and dysplasia of the cerebellum might be related to the presence of the trisomy 7 mosaicism on the cerebellum. Our observation strengthens the hypothesis that the phenotype observed in patients with SRS with UPD(7)m might also result from an undetected low level of trisomy 7 mosaicism that could best be revealed by performing cytogenetic investigations.