Characterization of the Beckwith-Wiedemann spectrum: Diagnosis and management

Molecular Basis and Diagnostic Approach to Isolated and Syndromic Lateralized Overgrowth in Childhood

OBJECTIVE

To demonstrate a high-yield molecular diagnostic workflow for lateralized overgrowth (LO), a congenital condition with abnormal enlargement of body parts, and to classify it by molecular genetics.

STUDY DESIGN

We categorized 186 retrospective cases of LO diagnosed between 2003 and 2023 into suspected Beckwith-Wiedemann spectrum, PIK3CA-related overgrowth spectrum (PROS), vascular overgrowth, or isolated LO, based on initial clinical assessments, to determine the appropriate first-tier molecular tests and tissue for analysis. Patients underwent testing for 11p15 epigenetic abnormalities or somatic variants in genes related to PI3K/AKT/mTOR, vascular proliferation, and RAS-MAPK cascades using blood or skin DNA. For cases with negative initial tests, a sequential cascade molecular approach was employed to improve diagnostic yield.

RESULTS

This approach led to a molecular diagnosis in 54% of cases, 89% of cases consistent with initial clinical suspicions, and 11% reclassified. Beckwith-Wiedemann spectrum was the most common cause, with 43% of cases exhibiting 11p15 abnormalities. PIK3CA-related overgrowth spectrum had the highest confirmation rate, with 74% of clinically diagnosed patients showing a PIK3CA variant. Vascular overgrowth demonstrated significant clinical overlap with other syndromes. A molecular diagnosis of isolated LO proved challenging, with only 21% of cases classifiable into a specific condition.

CONCLUSIONS

LO is underdiagnosed from a molecular viewpoint and to date has had no diagnostic guidelines, which is crucial for addressing potential cancer predisposition, enabling precision medicine treatments, and guiding management. This study sheds light on the molecular etiology of LO, highlighting the importance of a tailored diagnostic approach and of selecting appropriate testing to achieve the highest diagnostic yield.

Single-nucleus multiomic analysis of Beckwith-Wiedemann syndrome liver reveals PPARA signaling enrichment and metabolic dysfunction

Beckwith-Wiedemann Syndrome (BWS) is an epigenetic overgrowth syndrome caused by methylation changes in the human 11p15 chromosomal locus. Patients with BWS exhibit tissue overgrowth, as well as an increased risk of childhood neoplasms in the liver and kidney. To understand the impact of these 11p15 changes, specifically in the liver, we performed single-nucleus RNA sequencing (snRNA-seq) and single-nucleus assay for transposase-accessible chromatin with sequencing (snATAC-seq) to generate paired, cell-type-specific transcriptional and chromatin accessibility profiles of both BWS-liver and nonBWS-liver nontumorous tissue. Our integrated RNA+ATACseq multiomic approach uncovered hepatocyte-specific enrichment and activation of the peroxisome proliferator-activated receptor α (PPARA) - a liver metabolic regulator. To confirm our findings, we utilized a BWS-induced pluripotent stem cell (iPSC) model, where cells were differentiated into hepatocytes. Our data demonstrates the dysregulation of lipid metabolism in BWS-liver, which coincided with observed upregulation of PPARA during hepatocyte differentiation. BWS liver cells exhibited decreased neutral lipids and increased fatty acid β-oxidation, relative to controls. We also observed increased reactive oxygen species (ROS) byproducts in the form of peroxidated lipids in BWS hepatocytes, which coincided with increased oxidative DNA damage. This study proposes a putative mechanism for overgrowth and cancer predisposition in BWS liver due to perturbed metabolism.

Joint effects of CD8A and ICOS in Long QT Syndrome (LQTS) and Beckwith-Wiedemann Syndrome (BWS)

BACKGROUND

Long QT Syndrome (LQTS) and Beckwith-Wiedemann Syndrome (BWS) are complex disorders with unclear origins, underscoring the need for in-depth molecular investigations into their mechanisms. The main aim of this study is to identify the shared key genes between LQTS and BWS, shedding light on potential common molecular pathways underlying these syndromes.

METHODS

The LQTS and BWS datasets are available for download from the GEO database. Differential expression genes (DEGs) were identified. Weighted gene co-expression network analysis (WGCNA) was used to detect significant modules and central genes. Gene enrichment analysis was performed. CIBERSORT was used for immune cell infiltration analysis. The predictive protein interaction (PPI) network of core genes was constructed using STRING, and miRNAs regulating central genes were screened using TargetScan.

RESULTS

Five hundred DEGs associated with Long QT Syndrome and Beckwith-Wiedemann Syndrome were identified. GSEA analysis revealed enrichment in pathways such as T cell receptor signaling, MAPK signaling, and adrenergic signaling in cardiac myocytes. Immune cell infiltration indicated higher levels of memory B cells and naive CD4 T cells. Four core genes (CD8A, ICOS, CTLA4, LCK) were identified, with CD8A and ICOS showing low expression in the syndromes and high expression in normal samples, suggesting potential inverse regulatory roles.

CONCLUSION

The expression of CD8A and ICOS is low in long QT syndrome and Beckwith-Wiedemann syndrome, indicating their potential as key genes in the pathogenesis of these syndromes. The identification of shared key genes between LQTS and BWS provides insights into common molecular mechanisms underlying these disorders, potentially facilitating the development of targeted therapeutic strategies.

Expanded phenotype and cancer risk in patients with Beckwith-Wiedemann spectrum caused by CDKN1C variants

Beckwith-Wiedemann spectrum (BWSp) is caused by genetic and epigenetic alterations on chromosome 11 that regulate cell growth and division. Considering the diverse phenotypic landscape in BWSp, the characterization of the CDKN1C molecular subtype remains relatively limited. Here, we investigate the role of CDKN1C in the broader BWSp phenotype. Notably, patients with CDKN1C variants appear to exhibit a different tumor risk than other BWSp molecular subtypes. We performed a comprehensive literature review using the search term "CDKN1C Beckwith" to identify 113 cases of patients with molecularly confirmed CDKN1C-BWSp. We then assessed the genotype and phenotype in a novel cohort of patients with CDKN1C-BWSp enrolled in the BWS Research Registry. Cardinal and suggestive features were evaluated for all patients reported, and tumor risk was established based on available reports. The most common phenotypes included macroglossia, omphalocele, and ear creases/pits. Tumor types reported from the literature included neuroblastoma, acute lymphocytic leukemia, superficial spreading melanoma, and intratubular germ cell neoplasia. Overall, this study identifies unique features associated with CDKN1C variants in BWSp, enabling more accurate clinical management. The absence of Wilms tumor and hepatoblastoma suggests that screening for these tumors may not be necessary, while the neuroblastoma risk warrants appropriate screening recommendations.

A rare case of extremely low birth weight infant with Beckwith-Wiedemann syndrome

INTRODUCTION

Beckwith-Wiedemann syndrome (BWS) manifests distinctive features, such as macroglossia, overgrowth, and abdominal wall defects. In this report, we describe a case of BWS in an extremely low birth weight infant diagnosed at three months after birth because of the intensive care for low birth weight.

PRESENTATION OF CASE

A female infant was delivered at 24 weeks and 6 days of gestation with a weight of 845 g. After birth, significant small intestinal intra-umbilical prolapse was observed, and abdominal wall closure using a sutureless method was performed on day zero. Careful neonatal management was performed; however, an episode of bloody stools led to a diagnosis of intestinal volvulus due to intestinal malrotation. At 119 days of age, the Ladd procedure was performed. Notably, during anaesthesia induction, features suggestive of BWS were observed, leading to its diagnosis.

DISCUSSION

Early diagnosis of BWS is vital because of its association with tumors. However, because she was an extremely low birth weight infant who required oral intubation and supine management for respiratory control, nevus flammeus and macroglossia were not observed. Therefore, BWS was not diagnosed for approximately three months after birth. It is important to recognize that omphalocele in extremely low birth weight infants is a risk factor for delayed diagnosis of BWS.

CONCLUSION

Timely diagnosis of BWS is critical because of its association with tumors and varied clinical presentations. Early screening, especially for tumors, and awareness among surgical practitioners can aid in timely interventions and improved patient outcomes.

Whole-exome sequencing reveals causative genetic variants for several overgrowth syndromes in molecularly negative Beckwith-Wiedemann spectrum

Background Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder caused by (epi)genetic alterations at 11p15. Because approximately 20% of patients test negative via molecular testing of peripheral blood leukocytes, the concept of Beckwith-Wiedemann spectrum (BWSp) was established to encompass a broader cohort with diverse and overlapping phenotypes. The prevalence of other overgrowth syndromes concealed within molecularly negative BWSp remains unexplored. Methods We conducted whole-exome sequencing (WES) on 69 singleton patients exhibiting molecularly negative BWSp. Variants were confirmed by Sanger sequencing or quantitative genomic PCR. We compared BWSp scores and clinical features between groups with classical BWS (cBWS), atypical BWS or isolated lateralised overgrowth (aBWS+ILO) and overgrowth syndromes identified via WES. Results Ten patients, one classified as aBWS and nine as cBWS, showed causative gene variants for Simpson-Golabi-Behmel syndrome (five patients), Sotos syndrome (two), Imagawa-Matsumoto syndrome (one), glycosylphosphatidylinositol biosynthesis defect 11 (one) or 8q duplication/9p deletion (one). BWSp scores did not distinguish between cBWS and other overgrowth syndromes. Birth weight and height in other overgrowth syndromes were significantly larger than in aBWS+ILO and cBWS, with varying intergroup frequencies of clinical features. Conclusion Molecularly negative BWSp encapsulates other syndromes, and considering both WES and clinical features may facilitate accurate diagnosis.

Clinical Case of Mild Tatton-Brown-Rahman Syndrome Caused by a Nonsense Variant in DNMT3A Gene

Tatton-Brown-Rahman syndrome is a rare autosomal dominant hereditary disease caused by pathogenic variants in the DNMT3A gene, which is an important participant in epigenetic regulation, especially during embryonic development, and is highly expressed in all tissues. The main features of the syndrome are high growth, macrocephaly, intellectual disability, and facial dysmorphic features. We present a clinical case of Tatton-Brown-Rahman syndrome in a ten-year-old boy with macrocephaly with learning difficulties, progressive eye impairment, and fatigue suspected by a deep learning-based diagnosis assistance system, Face2Gene. The proband underwent whole-exome sequencing, which revealed a recurrent nonsense variant in the 12th exon of the DNMT3A, leading to the formation of a premature stop codon-NM_022552.5:c.1443C>A (p.Tyr481Ter), in a heterozygous state. This variant was not found in parents, confirming its de novo status. The patient case described here contributes to the understanding of the clinical diversity of Tatton-Brown-Raman syndrome with a mild clinical presentation that expands the phenotypic spectrum of the syndrome. We report the first recurrent nonsense variant in the DNMT3A gene, suggesting a mutational hot-spot. Differential diagnoses of this syndrome with Sotos syndrome, Weaver syndrome, and Cowden syndrome, as well as molecular confirmation, are extremely important, since the presence of certain types of pathogenic variants in the DNMT3A gene significantly increases the risk of developing acute myeloid leukemia.

GestaltMML: Enhancing Rare Genetic Disease Diagnosis through Multimodal Machine Learning Combining Facial Images and Clinical Texts

Individuals with suspected rare genetic disorders often undergo multiple clinical evaluations, imaging studies, laboratory tests and genetic tests, to find a possible answer over a prolonged period of time. Addressing this "diagnostic odyssey" thus has substantial clinical, psychosocial, and economic benefits. Many rare genetic diseases have distinctive facial features, which can be used by artificial intelligence algorithms to facilitate clinical diagnosis, in prioritizing candidate diseases to be further examined by lab tests or genetic assays, or in helping the phenotype-driven reinterpretation of genome/exome sequencing data. Existing methods using frontal facial photos were built on conventional Convolutional Neural Networks (CNNs), rely exclusively on facial images, and cannot capture non-facial phenotypic traits and demographic information essential for guiding accurate diagnoses. Here we introduce GestaltMML, a multimodal machine learning (MML) approach solely based on the Transformer architecture. It integrates facial images, demographic information (age, sex, ethnicity), and clinical notes (optionally, a list of Human Phenotype Ontology terms) to improve prediction accuracy. Furthermore, we also evaluated GestaltMML on a diverse range of datasets, including 528 diseases from the GestaltMatcher Database, several in-house datasets of Beckwith-Wiedemann syndrome (BWS, over-growth syndrome with distinct facial features), Sotos syndrome (overgrowth syndrome with overlapping features with BWS), NAA10-related neurodevelopmental syndrome, Cornelia de Lange syndrome (multiple malformation syndrome), and KBG syndrome (multiple malformation syndrome). Our results suggest that GestaltMML effectively incorporates multiple modalities of data, greatly narrowing candidate genetic diagnoses of rare diseases and may facilitate the reinterpretation of genome/exome sequencing data.

Hallmark discoveries in the biology of Wilms tumour

The modern study of Wilms tumour was prompted nearly 50 years ago, when Alfred Knudson proposed the 'two-hit' model of tumour development. Since then, the efforts of researchers worldwide have substantially expanded our knowledge of Wilms tumour biology, including major advances in genetics - from cloning the first Wilms tumour gene to high-throughput studies that have revealed the genetic landscape of this tumour. These discoveries improve understanding of the embryonal origin of Wilms tumour, familial occurrences and associated syndromic conditions. Many efforts have been made to find and clinically apply prognostic biomarkers to Wilms tumour, for which outcomes are generally favourable, but treatment of some affected individuals remains challenging. Challenges are also posed by the intratumoural heterogeneity of biomarkers. Furthermore, preclinical models of Wilms tumour, from cell lines to organoid cultures, have evolved. Despite these many achievements, much still remains to be discovered: further molecular understanding of relapse in Wilms tumour and of the multiple origins of bilateral Wilms tumour are two examples of areas under active investigation. International collaboration, especially when large tumour series are required to obtain robust data, will help to answer some of the remaining unresolved questions.

Cancer predisposition signaling in Beckwith-Wiedemann Syndrome drives Wilms tumor development

BACKGROUND

Wilms tumor (WT) exhibits structural and epigenetic changes at chromosome 11p15, which also cause Beckwith-Wiedemann Syndrome (BWS). Children diagnosed with BWS have increased risk for WT. The aim of this study is to identify the molecular signaling signatures in BWS driving these tumors.

METHODS

We performed whole exome sequencing, methylation array analysis, and gene expression analysis on BWS-WT samples. Our data were compared to publicly available nonBWS data. We categorized WT from BWS and nonBWS patients by assessment of 11p15 methylation status and defined 5 groups- control kidney, BWS-nontumor kidney, BWS-WT, normal-11p15 nonBWS-WT, altered-11p15 nonBWS-WT.

RESULTS

BWS-WT samples showed single nucleotide variants in BCORL1, ASXL1, ATM and AXL but absence of recurrent gene mutations associated with sporadic WT. We defined a narrow methylation range stratifying nonBWS-WT samples. BWS-WT and altered-11p15 nonBWS-WT showed enrichment of common and unique molecular signatures based on global differential methylation and gene expression analysis. CTNNB1 overexpression and broad range of interactions were seen in the BWS-WT interactome study.

CONCLUSION

While WT predisposition in BWS is well-established, as are 11p15 alterations in nonBWS-WT, this study focused on stratifying tumor genomics by 11p15 status. Further investigation of our findings may identify novel therapeutic targets in WT oncogenesis.

Beckwith-Wiedemann syndrome mimicking the classical form of congenital adrenal hyperplasia in newborn screening

Beckwith-Wiedemann syndrome (BWS) is a common genetic congenital disease characterized by somatic overgrowth and its broad clinical spectrum includes pre- and post-natal macrosomia, macroglossia, visceromegaly, increased risk of neonatal hypoglycemia, and development of embryonic tumors. BWS occurs due to genetic/epigenetic changes involving growth-regulating genes, located on region 11p15, with an important genotype-phenotype correlation. Congenital adrenal hyperplasia (CAH) comprises a spectrum of autosomal recessive diseases presenting a variety of clinical manifestations due to a deficiency in one of the enzymes involved in cortisol secretion. Early diagnosis based on newborn screening prevents the adrenal crisis and early infant death. However, high 17-hydroxyprogesterone (17-OHP) levels can occur in newborns or premature infants without CAH, in situations of stress due to maternal or neonatal factors. Here, we report new cases of false-positive diagnosis of 21-hydroxylase deficiency during newborn screening - two girls and one boy with BWS. Methylation-specific multiplex ligation-dependent probe amplification revealed a gain of methylation in the H19 differentially methylated region. Notably, all three cases showed a complete normalization of biochemical changes, highlighting the transient nature of these hormonal findings that imitate the classical form of CAH. This report sheds light on a new cause of false-positive 21-hydroxylase deficiency diagnosis during newborn screening: Beckwith-Wiedemann syndrome.

Human Reproduction and Disturbed Genomic Imprinting

Genomic imprinting is a specific mode of gene regulation which particularly accounts for the factors involved in development. Its disturbance affects the fetus, the course of pregnancy and even the health of the mother. In children, aberrant imprinting signatures are associated with imprinting disorders (ImpDis). These alterations also affect the function of the placenta, which has consequences for the course of the pregnancy. The molecular causes of ImpDis comprise changes at the DNA level and methylation disturbances (imprinting defects/ImpDefs), and there is an increasing number of reports of both pathogenic fetal and maternal DNA variants causing ImpDefs. These ImpDefs can be inherited, but prediction of the pregnancy complications caused is difficult, as they can cause miscarriages, aneuploidies, health issues for the mother and ImpDis in the child. Due to the complexity of imprinting regulation, each pregnancy or patient with suspected altered genomic imprinting requires a specific workup to identify the precise molecular cause and also careful clinical documentation. This review will cover the current knowledge on the molecular causes of aberrant imprinting signatures and illustrate the need to identify this basis as the prerequisite for personalized genetic and reproductive counselling of families.

First-time application of droplet digital PCR for methylation testing of the 11p15.5 imprinting regions

BACKGROUND

Beckwith-Wiedemann syndrome and Silver-Russel syndrome are two imprinting disorders caused by opposite molecular alterations in 11p15.5. With the current diagnostic tests, their molecular diagnosis is challenging due to molecular heterogeneity and mosaic occurrence of the most frequent alterations. As the determination of precise (epi)genotype of patients is relevant as the basis for a personalized treatment, different approaches are needed to increase the sensitivity of diagnostic testing of imprinting disorders.

METHODS

We established methylation-specific droplet digital PCR approaches (MS-ddPCR) for the two imprinting centers in 11p15.5, and analyzed patients with paternal uniparental disomy of chromosome 11p15.5 (upd(11)pat) and other imprinting defects in the region. The results were compared to those from MS-MLPA (multiplex ligation-dependent probe amplification) and MS-pyrosequencing.

RESULTS

MS-ddPCR confirmed the molecular alterations in all patients and the results matched well with MS-MLPA. The results of MS-pyrosequencing varied between different runs, whereas MS-ddPCR results were reproducible.

CONCLUSION

We show for the first time that MS-ddPCR is a reliable and easy applicable method for determination of MS-associated changes in imprinting disorders. It is therefore an additional tool for multimethod diagnostics of imprinting disorders suitable to improve the diagnostic yield.

Prevalence of Beckwith Wiedemann Syndrome and Risk of Embryonal Tumors in Children Born with Omphalocele

AIM OF THE STUDY

Children with omphalocele have an increased prevalence of Beckwith Wiedemann syndrome (BWS) and thus a suspected increased risk of developing embryonal tumors, e.g. Wilms tumor, hepatoblastoma, neuroblastoma and rhabdomyosarcoma. The aim of this study was to examine the prevalence of BWS and the risk of embryonal tumors amongst patients born with omphalocele.

METHODS

A population-based cohort was used, including all children born in Sweden 1/1 1997-31/12 2016. Patients with omphalocele were identified through the Swedish National Patient Register and the Swedish Medical Birth Register. For each case of omphalocele ten age and sex matched individuals unexposed for omphalocele were randomly selected for comparison. Data on BWS and embryonal tumors were collected from the Swedish National Patient Register and the Swedish National Cancer Register.

MAIN RESULTS

Out of 207 cases of omphalocele, 15 (7.2%) were diagnosed with BWS. None of the children with omphalocele had yet developed any kind of embryonal tumor (median follow-up time 8 years). None of the 2070 controls were diagnosed with BWS but 3 (0.1%) of them had developed embryonal tumors during a median follow-up time of 10 years.

CONCLUSIONS

In this study the prevalence of BWS amongst children born with omphalocele is in the lower range of previously reported figures. Also, the prevalence of embryonal tumors amongst children with BWS is lower than expected and the risk of embryonal tumors in children with omphalocele and BWS might not be as high as previously stated. This must be taken into consideration when counseling parents prenatally.

TYPE OF STUDY

National register cohort study.

LEVEL OF EVIDENCE

II.

Beckwith-Wiedemann Syndrome in Newborn of Mother with HELLP Syndrome/Preeclampsia: An Analysis of Literature and Case Report with Fetal Growth Restriction and Absence of CDKN1C Typical Pathogenic Genetic Variation

Beckwith-Wiedemann Syndrome (BWS) is an imprinting disorder, which manifests by overgrowth and predisposition to embryonal tumors. The evidence on the relationship between maternal complications such as HELLP (hemolysis, elevated liver enzymes, and low platelet count) and preeclampsia and the development of BWS in offspring is scarce. A comprehensive clinical evaluation, with genetic testing focused on screening for mutations in the CDKN1C gene, which is commonly associated with BWS, was conducted in a newborn diagnosed with BWS born to a mother with a history of preeclampsia and HELLP syndrome. The case study revealed typical clinical manifestations of BWS in the newborn, including hemihyperplasia, macroglossia, midfacial hypoplasia, omphalocele, and hypoglycemia. Surprisingly, the infant also exhibited fetal growth restriction, a finding less commonly observed in BWS cases. Genetic analysis, however, showed no mutations in the CDKN1C gene, which contrasts with the majority of BWS cases. This case report highlights the complex nature of BWS and its potential association with maternal complications such as preeclampsia and HELLP syndrome. The atypical presence of fetal growth restriction in the newborn and the absence of CDKN1C gene mutations have not been reported to date in BWS.

Occurrence of Hepatoblastomas in Patients with Beckwith-Wiedemann Spectrum (BWSp)

Patients with Beckwith-Wiedemann syndrome (BWS), an epigenetic imprinting disorder involving alterations in genes at the 11p15 chromosomal location, are predisposed to develop hepatoblastomas (HBs), which are rare embryonal liver tumors. Tumors can develop after a BWS diagnosis or, conversely, can be the presenting feature leading to a subsequent diagnosis. While HBs are the cardinal tumors of BWS, not all patients with the BWS spectrum will develop HBs. This observation has led to many hypotheses, including genotype-associated risk, tissue mosaicism, and tumor-specific second hits. To explore these hypotheses, we present the largest cohort of patients with BWS and HBs to date. Our cohort comprised 16 cases, and we broadened our sample size by searching the literature for all cases of BWS with HBs. From these isolated case studies, we amassed another 34 cases, bringing the total number to 50 cases of BWS-HB. We observed that paternal uniparental isodisomy (upd(11)pat) was the most common genotype, representing 38% of cases. The next most common genotype was IC2 LOM, representing 14% of cases. Five patients had clinical BWS without a molecular diagnosis. To investigate the potential mechanism of HBs in BWS, we analyzed normal liver and HB samples from eight cases and isolated tumor samples from another two cases. These samples underwent methylation testing, and 90% of our tumor samples underwent targeted cancer next-generation sequencing (NGS) panels. These matched samples provided novel insights into the oncogenesis of HBs in BWS. We found that 100% of the HBs that underwent NGS panel testing had variants in the CTNNB1 gene. We further identified three distinct groups of BWS-HB patients based on epigenotype. We also demonstrated epigenotype mosaicism, where 11p15 alterations can differ between the blood, HB, and normal liver. In light of this epigenotype mosaicism, tumor risk assessment based on blood profiling may not be accurate. Therefore, universal screening is recommended for all patients with BWS.

Investigation of 11p15.5 Methylation Defects Associated with Beckwith-Wiedemann Spectrum and Embryonic Tumor Risk in Lateralized Overgrowth Patients

The Beckwith-Wiedemann spectrum (BWSp) ranges from isolated lateralized overgrowth (ILO) to classic phenotypes. In this broad clinical spectrum, an epigenetic alteration on chromosome 11p15.5 can be detected. The risk for embryonal tumors is high, especially in patients with lateralized overgrowth (LO). The aim of this study is to investigate epigenetic alterations in 11p15.5 and tumor risk in 87 children with LO. The methylation level of 11p15.5 was examined in the blood of all patients and in skin samples or buccal swabs from 40 patients with negative blood tests; 63.2% of patients were compatible with the ILO phenotype, 18.4% were atypical, and 18.4% were classic. The molecular diagnosis rate was 81.2% for the atypical and classic phenotypes, and 10.9% for the ILO phenotype. In patients with epigenetic alterations, LO was statistically significantly more severe than in test negatives. Tumors developed in six (6.9%) of the total 87 patients with LO; four belonged to the atypical or classical phenotype (12.5%) and two to ILO (3.5%). Three of the four patients with atypical/classical phenotypes had pUPD11, one had IC1-GOM alteration, and two ILO patients were negative. We conclude that LO patients should be monitored for tumor risk even if their epigenetic tests are negative.

Partial Glossectomy Combined With Radiofrequency Ablation for Macroglossia in Beckwith-Wiedemann Syndrome

OBJECTIVE

As the most common feature of Beckwith-Wiedemann syndrome (BWS), macroglossia may influence the quality of life, maxillofacial growth, and speech development of children. The retrospective study aimed to investigate the therapeutic effect of partial glossectomy combined with radiofrequency ablation (RFA) for macroglossia patients in BWS.

METHODS

A retrospective study was conducted in BWS-derived macroglossia patients who underwent partial glossectomy combined with RFA from May 2019 to January 2021. In total, 35 patients consisting of 17 males and 18 females met the inclusion criteria and underwent surgery by the same plastic surgeon. Demographic characteristics, BWS features, operation details, preoperative and postoperative outcomes, satisfaction evaluations, and subgroup analysis were collected and assessed.

RESULTS

Of the 35 patients involved, the average age at the time of surgery was 14.05±8.08 months, and the average surgery duration was 48.17±6.72 minutes. Only 1 patient suffered ventral tongue wound dehiscence, and the rest of the patients did not develop any other complications. The severity and frequency of tongue protrusion, drooling, snoring, and feeding difficulty were significantly ameliorated. The patient's parents showed satisfaction towards the overall surgery, tongue's appearance, and tongue's motor function. Tongue's height decreased from 32.09±1.16 mm before the operation to 29.29±1.33 mm after the operation.

CONCLUSION

The partial glossectomy combined RFA exerts a safe, effective and viable technique to treat BWS-derived macroglossia.

Implications of an Underlying Beckwith-Wiedemann Syndrome for Wilms Tumor Treatment Strategies

Beckwith-Wiedemann Syndrome (BWS) is a pediatric overgrowth disorder involving a predisposition to embryonal tumors. Most of the tumors associated with BWS occur in the first 8-10 years of life, and the most common is Wilms tumor (WT). BWS clinical heterogeneity includes subtle overgrowth features or even silent phenotypes, and WT may be the presenting symptom of BWS. WT in BWS individuals exhibit distinct characteristics from those of sporadic WT, and the management of these patients needs a peculiar approach. The most important feature is a higher risk of developing bilateral disease at some time in the course of the illness (synchronous bilateral disease at diagnosis or metachronous recurrence after initial presentation with unilateral disease). Accordingly, neoadjuvant chemotherapy is the recommended approach also for BWS patients with unilateral WT to facilitate nephron-sparing surgical approaches. This review emphasizes the importance of early BWS recognition, particularly if a WT has already occurred, as this will result in an urgent consideration of first-line cancer therapy.

Familial Beckwith-Wiedemann syndrome in a multigenerational family: Forty years of careful phenotyping

Beckwith-Wiedemann Spectrum (BWSp) is an overgrowth and cancer predisposition disorder characterized by a wide spectrum of phenotypic manifestations including macroglossia, abdominal wall defects, neonatal hypoglycemia, and predisposition to embryonal tumors. In 1981, Best and Hoekstra reported four patients with BWSp in a single family which suggested autosomal dominant inheritance, but standard clinical testing for BWSp was not available during this time. Meticulous phenotyping of this family has occurred over the past 40 years of follow-up with additional family members being identified and samples collected for genetic testing. Genetic testing revealed a pathogenic mutation in CDKN1C, consistent with the most common cause of familial BWSp. CDKN1C mutations account for just 5% of sporadic cases of BWSp. Here, we report the variable presentation of BWSp across the individuals affected by the CDKN1C mutation and other extended family members spanning multiple generations, all examined by the same physician. Additional phenotypes thought to be atypical in patients with BWSp were reported which included cardiac abnormalities. The incidence of tumors was documented in extended family members and included rhabdomyosarcoma, astrocytoma, and thyroid carcinoma, which have previously been reported in patients with BWSp. These observations suggest that in addition to the inheritance of the CDKN1C variant, there are modifying factors in this family driving the phenotypic spectrum observed. Alternative theories are suggested to explain the etiology of clinical variability including diffused mosaicism, anticipation, and the presence of additional variants tracking in the family. This study highlights the necessity of long-term follow-up in patients with BWSp and consideration of individual familial characteristics in the context of phenotype and/or (epi)genotype associations.

Performance Metrics of the Scoring System for the Diagnosis of the Beckwith-Wiedemann Spectrum (BWSp) and Its Correlation with Cancer Development

Different scoring systems for the clinical diagnosis of the Beckwith-Wiedemann spectrum (BWSp) have been developed over time, the most recent being the international consensus score. Here we try to validate and provide data on the performance metrics of these scoring systems of the 2018 international consensus and the previous ones, relating them to BWSp features, molecular tests, and the probability of cancer development in a cohort of 831 patients. The consensus scoring system had the best performance (sensitivity 0.85 and specificity 0.43). In our cohort, the diagnostic yield of tests on blood-extracted DNA was low in patients with a low consensus score (~20% with a score = 2), and the score did not correlate with cancer development. We observed hepatoblastoma (HB) in 4.3% of patients with UPD(11)pat and Wilms tumor in 1.9% of patients with isolated lateralized overgrowth (ILO). We validated the efficacy of the currently used consensus score for BWSp clinical diagnosis. Based on our observation, a first-tier analysis of tissue-extracted DNA in patients with <4 points may be considered. We discourage the use of the consensus score value as an indicator of the probability of cancer development. Moreover, we suggest considering cancer screening for negative patients with ILO (risk ~2%) and HB screening for patients with UPD(11)pat (risk ~4%).

[Preterm with Macroglossia and Persistent Hypoglycemia - Beckwith-Wiedemann Syndrome]

Beckwith-Wiedemann syndrome (BWS) is a genetic disease with phenotypic variability and the following signs: macroglossia, asymmetry, lateralised overgrowth, overgrowth of the internal organs, abdominal wall defects, neonatal hypoglycemia and increased risk of embryonic tumours. The prevalence is reported as being between 1 in 10,000 and 1 in 21,000 live births. The disease is caused by molecular changes in gene clusters on the short arm of chromosome 11 region P15.5. We present the case of a female, born preterm at 32 0/7 weeks. A UPD(11)pat-mutation was diagnosed postnatally. The particular feature of her case was an early tongue reduction surgery which was necessary because of drinking and breathing difficulties. Long-lasting hypoglycemia was difficult to treat.

Histopathologic Features of Adrenal Cortical Carcinoma

Adrenal cortical carcinoma (ACC) is a rare and aggressive malignancy that poses challenging issues regarding the diagnostic workup. Indeed, no presurgical technique or clinical parameters can reliably distinguish between adrenal cortical adenomas, which are more frequent and have a favorable outcome, and ACC, and the final diagnosis largely relies on histopathologic analysis of the surgical specimen. However, even the pathologic assessment of malignancy in an adrenal cortical lesion is not straightforward and requires a combined evaluation of multiple histopathologic features. Starting from the Weiss score, which was developed in 1984, several histopathologic scoring systems have been designed to tackle the difficulties of ACC diagnosis. Dealing with specific histopathologic variants (eg, Liss-Weiss-Bisceglia scoring system for oncocytic ACC) or patient characteristics (eg, Wieneke index in the pediatric setting), these scores remarkably improved the diagnostic workup of ACC and its subtypes. Nevertheless, cases with misleading features or discordant correlations between pathologic findings and clinical behavior still occur. Owing to multicentric collaborative studies integrating morphologic features with ancillary immunohistochemical markers and molecular analysis, ACC has eventually emerged as a multifaceted, heterogenous malignancy, and, while innovative and promising approaches are currently being tested, the future clinical management of patients with ACC will mainly rely on personalized medicine and target-therapy protocols. At the dawn of the new Fifth World Health Organization classification of endocrine tumors, this review will tackle ACC from the pathologist's perspective, thus focusing on the main available diagnostic, prognostic, and predictive tissue-tethered features and biomarkers and providing relevant clinical and molecular correlates.

Beckwith-Wiedemann syndrome with long QT caused by a deletion involving KCNQ1 but not KCNQ1OT1:TSS-DMR

Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder with characteristic features, such as overgrowth, macroglossia, and exomphalos. Hypomethylation of the KCNQ1OT1:TSS-differentially methylated region (DMR) on the 11p15.5 imprinted region is the most common etiology of BWS. KCNQ1 on 11p15.5 is expressed from the maternally inherited allele in most tissues, but is biparentally expressed in the heart, and maternal KCNQ1 transcription is required to establish the maternal DNA imprint in the KCNQ1OT1:TSS-DMR. Loss of function variants in KCNQ1 result in long QT syndrome type 1 (LQT1). To date, eight patients with BWS due to KCNQ1 splice variants or structural abnormalities involving KCNQ1 but not the KCNQ1OT1:TSS-DMR have been reported (KCNQ1-BWS), and four of them had LQT1. We report a Japanese boy with BWS and LQT1 presenting with extreme hypomethylation of the KCNQ1OT1:TSS-DMR caused by a de novo 215-kb deletion including KCNQ1 but not the KCNQ1OT1:TSS-DMR on the maternal allele. He was born by emergency cesarean section due to suspicion of placental abruption at 30 weeks of gestation. His birth weight and length were +1.6 SD and +1.0 SD, respectively. His placental weight was +3.9 SD, and histological examination of his placenta was consistent with mesenchymal dysplasia. He had BWS clinical features, including macroglossia, ear creases and pits, body asymmetry, and rectus abdominis muscle dehiscence, and BWS was therefore diagnosed. LQT1 was first noticed at three months in a preoperative examination for lingual frenectomy. The summarized data of our patient and the previously reported eight patients in KCNQ1-BWS showed more frequent and earlier preterm births and smaller sized birth weight in KCNQ1-BWS cases than those with BWS caused by epimutation of the KCNQ1OT1:TSS-DMR. In addition, in five of nine patients with KCNQ1-BWS, LQT1 was detected, and two of them were identified at school age. In our patient and in another single case with LQT1, the LQT1 was not detected early despite neonatal ECG monitoring. For BWS patients with extreme hypomethylation of the KCNQ1OT1:TSS-DMR, searching for CNVs involving KCNQ1 and mutation screening for KCNQ1 should be considered together with periodic ECG monitoring. (338/500 words).

Placental Mesenchymal Dysplasia and Beckwith-Wiedemann Syndrome

Placental mesenchymal dysplasia (PMD) is characterized by placentomegaly, aneurysmally dilated chorionic plate vessels, thrombosis of the dilated vessels, and large grapelike vesicles, and is often mistaken for partial or complete hydatidiform mole with a coexisting normal fetus. Androgenetic/biparental mosaicism (ABM) has been found in many PMD cases. Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder with complex and diverse phenotypes and an increased risk of developing embryonal tumors. There are five major causative alterations: loss of methylation of imprinting control region 2 (KCNQ1OT1:TSS-DMR) (ICR2-LOM), gain of methylation at ICR1 (H19/IGF2:IG-DMR) (ICR1-GOM), paternal uniparental disomy of 11 (pUPD11), loss-of-function variants of the CDKN1C gene, and paternal duplication of 11p15. Additional minor alterations include genetic variants within ICR1, paternal uniparental diploidy/biparental diploidy mosaicism (PUDM, also called ABM), and genetic variants of KCNQ1. ABM (PUDM) is found in both conditions, and approximately 20% of fetuses from PMD cases are BWS and vice versa, suggesting a molecular link. PMD and BWS share some molecular characteristics in some cases, but not in others. These findings raise questions concerning the timing of the occurrence of the molecularly abnormal cells during the postfertilization period and the effects of these abnormalities on cell fates after implantation.

Molecular networks of hepatoblastoma predisposition and oncogenesis in Beckwith-Wiedemann syndrome

Beckwith-Wiedemann Syndrome (BWS) is the most common human overgrowth disorder caused by structural and epigenetic changes to chromosome 11p15. Patients with BWS are predisposed to developing hepatoblastoma (HB). To better understand the mechanism of HB oncogenesis in this cancer predisposition background, we performed the first multi-dimensional study of HB samples collected from patients diagnosed with BWS. This multi-omic investigation of seven BWS HB and five matched nontumor BWS liver samples from 7 unique patients included examination of whole exome sequences, messenger RNA/microRNA expression, and methylation levels to elucidate the genomic, transcriptomic, and epigenomic landscape of BWS-associated HB. We compared the transcriptional profiles of the BWS samples, both HB and nontumor, to that of control livers. Genes differentially expressed across BWS tissues were identified as BWS HB predisposition factors; this gene group included cell cycle regulators, chromatin organizers, and WNT, mitogen-activated protein kinase (MAPK), and phosphoinositide 3-kinase (PI3K)/AKT members. We also compared transcriptional changes associated with non-syndromic HB carrying BWS-like 11p15 alterations compared to those without, as well as to BWS HB. Through this analysis, we identified factors specific to 11p15-altered HB oncogenesis, termed the BWS oncogenesis network. We propose that 11p15 alterations drive HB oncogenesis by initially dysregulating cell-cycle regulators and chromatin organizers, including histone deacetylase 1 (HDAC1), ATP-dependent helicase X, and F-Box and WD repeat domain containing 7. Furthermore, we found oncogenic factors such as dickkopf WNT signaling pathway inhibitor 1 and 4, WNT16, forkhead box O3 (FOXO3), and MAPK10 are differentially expressed in 11p15-altered HB in both the BWS and non-syndromic backgrounds. These genes warrant further investigation as diagnostic or therapeutic targets.

Clinical and molecular characterization of patients affected by Beckwith-Wiedemann spectrum conceived through assisted reproduction techniques

The prevalence of Beckwith–Wiedemann spectrum (BWSp) is tenfold increased in children conceived through assisted reproductive techniques (ART). More than 90% of ART‐BWSp patients reported so far display imprinting center 2 loss‐of‐methylations (IC2‐LoM), versus 50% of naturally conceived BWSp patients. We describe a cohort of 74 ART‐BWSp patients comparing their features with a cohort of naturally conceived BWSp patients, with the ART‐BWSp patients previously described in literature, and with the general population of children born from ART. We found that the distribution of UPD(11)pat was not significantly different in ART and naturally conceived patients. We observed 68.9% of IC2‐LoM and 16.2% of mosaic UPD(11)pat in our ART cohort, that strongly differ from the figure reported in other cohorts so far. Since UPD(11)pat likely results from post‐fertilization recombination events, our findings allows to hypothesize that more complex molecular mechanisms, besides methylation disturbances, may underlie BWSp increased risk in ART pregnancies. Moreover, comparing the clinical features of ART and non‐ART BWSp patients, we found that ART‐BWSp patients might have a milder phenotype. Finally, our data show a progressive increase in the prevalence of BWSp over time, paralleling that of ART usage in the last decades.

Molecular Basis of Beckwith–Wiedemann Syndrome Spectrum with Associated Tumors and Consequences for Clinical Practice

Simple Summary

Beckwith–Wiedemann syndrome (BWS, OMIM 130650) is an inborn overgrowth disorder caused by molecular alterations in chromosome 11p15.5. These molecular changes affect so-called imprinted genes, i.e., genes which underlie a complex regulation which is linked to the parental origin of the gene copy. Thus, either the maternal gene copy is expressed or the paternal, but this balanced regulation is prone to disturbances. In fact, different types of molecular variants have been identified in BWS, resulting in a variable phenotype; thus, it was consented that the syndromic entity was extended to the Beckwith–Wiedemann spectrum (BWSp). Some molecular subgroups of BWSp are associated with an increased embryonic tumor risk and have different likelihoods for specific tumors. Therefore, the precise determination of the molecular subgroup is needed for precise monitoring and treatment, but the molecular diagnostic procedure has several limitations and challenges which have to be considered.

Abstract

Beckwith–Wiedemann syndrome (BWS, OMIM 130650) is a congenital imprinting condition with a heterogenous clinical presentation of overgrowth and an increased childhood cancer risk (mainly nephroblastoma, hepatoblastoma or neuroblastoma). Due to the varying clinical presentation encompassing classical, clinical BWS without a molecular diagnosis and BWS-related phenotypes with an 11p15.5 molecular anomaly, the syndromic entity was extended to the Beckwith–Wiedemann spectrum (BWSp). The tumor risk of up to 30% depends on the molecular subtype of BWSp with causative genetic or epigenetic alterations in the chromosomal region 11p15.5. The molecular diagnosis of BWSp can be challenging for several reasons, including the range of causative molecular mechanisms which are frequently mosaic. The molecular basis of tumor formation appears to relate to stalled cellular differentiation in certain organs that predisposes persisting embryonic cells to accumulate additional molecular defects, which then results in a range of embryonal tumors. The molecular subtype of BWSp not only influences the overall risk of neoplasia, but also the likelihood of specific embryonal tumors.

The embryo battle against adverse genomes: Are de novo terminal deletions the rescue of unfavorable zygotic imbalances?

De novo distal deletions are structural variants considered to be already present in the zygote. However, investigations especially in the prenatal setting have documented that they are often in mosaic with cell lines in which the same deleted chromosome shows different types of aberrations such as: 1) neutral copy variants with loss of heterozygosity that replace the deleted region with equivalent portions of the homologous chromosome and create distal uniparental disomy (UPD); 2) derivative chromosomes where the deleted one ends with the distal region of another chromosome or has the shape of a ring; 3) U-type mirror dicentric or inv-dup del rearrangements. Unstable dicentrics had already been entailed as causative of terminal deletions even when no trace of the reciprocal inv-dup del had been detected. To clarify the mechanism of origin of distal deletions, we examined PubMed using as keywords: complex/mosaic chromosomal deletions, distal UPD, U-type dicentrics, inv-dup del chromosomes, excluding the recurrent inv-dup del(8p)s which are known to originate by NAHR at the maternal meiosis. The literature has shown that U-type dicentrics leading to nearly complete trisomy and therefore incompatible with zygotic survival underlie many types of de novo unbalanced rearrangements, including terminal deletions. In the early embryo, the position of the postzygotic breaks of the dicentric, the different ways of acquiring telomeres by the broken portions and the selection of the most favorable cell lines in the different tissues determine the prevalence of one or the other rearrangement. Multiple lines with simple terminal deletions, inv-dup dels, unbalanced translocations and segmental UPDs can coexist in various mosaic combinations although it is rare to identify them all in the blood. Regarding the origin of the dicentric, among the 30 cases of non-recurrent inv-dup del with sufficient genotyping information, paternal origin was markedly prevalent with consistently identical polymorphisms within the duplication region, regardless of parental origin. The non-random parental origin made any postzygotic origin unlikely and suggested the occurrence of these dicentrics mainly in spermatogenesis. This study strengthens the evidence that non-recurrent de novo structural rearrangements are often secondary to the rescue of a zygotic genome incompatible with embryo survival.

Revisiting the Threshold for Cancer Genetics Referral in Patients With Wilms Tumor

The Oncology Grand Rounds series is designed to place original reports published in the Journal into clinical context. A case presentation is followed by a description of diagnostic and management challenges, a review of the relevant literature, and a summary of the authors' suggested management approaches. The goal of this series is to help readers better understand how to apply the results of key studies, including those published in the Journal of Clinical Oncology , to patients seen in their own clinical practice.

Epimutation in inherited metabolic disorders: the influence of aberrant transcription in adjacent genes

Epigenetic diseases can be produced by a stable alteration, called an epimutation, in DNA methylation, in which epigenome alterations are directly involved in the underlying molecular mechanisms of the disease. This review focuses on the epigenetics of two inherited metabolic diseases, epi-cblC, an inherited metabolic disorder of cobalamin (vitamin B₁₂) metabolism, and alpha-thalassemia type α-ZF, an inherited disorder of α2-globin synthesis, with a particular interest in the role of aberrant antisense transcription of flanking genes in the generation of epimutations in CpG islands of gene promoters. In both disorders, the epimutation is triggered by an aberrant antisense transcription through the promoter, which produces an H3K36me3 histone mark involved in the recruitment of DNA methyltransferases. It results from diverse genetic alterations. In alpha-thalassemia type α-ZF, a deletion removes HBA1 and HBQ1 genes and juxtaposes the antisense LUC7L gene to the HBA2 gene. In epi-cblC, the epimutation in the MMACHC promoter is produced by mutations in the antisense flanking gene PRDX1, which induces a prolonged antisense transcription through the MMACHC promoter. The presence of the epimutation in sperm, its transgenerational inheritance via the mutated PRDX1, and the high expression of PRDX1 in spermatogonia but its nearly undetectable transcription in spermatids and spermatocytes, suggest that the epimutation could be maintained during germline reprogramming and despite removal of aberrant transcription. The epivariation seen in the MMACHC promoter (0.95 × 10^-3) is highly frequent compared to epivariations affecting other genes of the Online Catalog of Human Genes and Genetic Disorders in an epigenome-wide dataset of 23,116 individuals. This and the comparison of epigrams of two monozygotic twins suggest that the aberrant transcription could also be influenced by post-zygotic environmental exposures.

Lateralized and Segmental Overgrowth in Children

Congenital disorders of lateralized or segmental overgrowth (LO) are heterogeneous conditions with increased tissue growth in a body region. LO can affect every region, be localized or extensive, involve one or several embryonic tissues, showing variable severity, from mild forms with minor body asymmetry to severe ones with progressive tissue growth and related relevant complications. Recently, next-generation sequencing approaches have increased the knowledge on the molecular defects in LO, allowing classifying them based on the deranged cellular signaling pathway. LO is caused by either genetic or epigenetic somatic anomalies affecting cell proliferation. Most LOs are classifiable in the Beckwith-Wiedemann spectrum (BWSp), PI3KCA/AKT-related overgrowth spectrum (PROS/AROS), mosaic RASopathies, PTEN Hamartoma Tumor Syndrome, mosaic activating variants in angiogenesis pathways, and isolated LO (ILO). These disorders overlap over common phenotypes, making their appraisal and distinction challenging. The latter is crucial, as specific management strategies are key: some LO is associated with increased cancer risk making imperative tumor screening since childhood. Interestingly, some LO shares molecular mechanisms with cancer: recent advances in tumor biological pathway druggability and growth downregulation offer new avenues for the treatment of the most severe and complicated LO.

Characteristics Associated with Tumor Development in Individuals Diagnosed with Beckwith-Wiedemann Spectrum: Novel Tumor-(epi)Genotype-Phenotype Associations in the BWSp Population

Beckwith–Wiedemann Spectrum (BWSp) is the most common epigenetic childhood cancer predisposition disorder. BWSp is caused by (epi)genetic changes affecting the BWS critical region on chromosome 11p15. Clinically, BWSp represents complex molecular and phenotypic heterogeneity resulting in a range of presentations from Classic BWS to milder features. The previously reported tumor risk based on Classic BWS cohorts is 8–10% and routine tumor screening has been recommended. This work investigated the tumor risk and correlation with phenotype within a cohort of patients from Classic BWS to BWSp using a mixed-methods approach to explore phenotype and epigenotype profiles associated with tumor development through statistical analyses with post-hoc retrospective case series review. We demonstrated that tumor risk across BWSp differs from Classic BWS and that certain phenotypic features are associated with specific epigenetic causes; nephromegaly and/or hyperinsulinism appear associated with cancer in some patients. We also demonstrated that prenatal and perinatal factors that are not currently part of the BWSp classification may factor into tumor risk. Additionally, blood testing results are not necessarily synonymous with tissue testing results. Together, it appears that the current understanding from Classic BWS of (epi)genetics and phenotype correlations with tumors is not represented in the BWSp. Further study is needed in this complex population.

The Role of Long Non-coding RNAs in Human Imprinting Disorders: Prospective Therapeutic Targets

Genomic imprinting is a term used for an intergenerational epigenetic inheritance and involves a subset of genes expressed in a parent-of-origin-dependent way. Imprinted genes are expressed preferentially from either the paternally or maternally inherited allele. Long non-coding RNAs play essential roles in regulating this allele-specific expression. In several well-studied imprinting clusters, long non-coding RNAs have been found to be essential in regulating temporal- and spatial-specific establishment and maintenance of imprinting patterns. Furthermore, recent insights into the epigenetic pathological mechanisms underlying human genomic imprinting disorders suggest that allele-specific expressed imprinted long non-coding RNAs serve as an upstream regulator of the expression of other protein-coding or non-coding imprinted genes in the same cluster. Aberrantly expressed long non-coding RNAs result in bi-allelic expression or silencing of neighboring imprinted genes. Here, we review the emerging roles of long non-coding RNAs in regulating the expression of imprinted genes, especially in human imprinting disorders, and discuss three strategies targeting the central long non-coding RNA UBE3A-ATS for the purpose of developing therapies for the imprinting disorders Prader-Willi syndrome and Angelman syndrome. In summary, a better understanding of long non-coding RNA-related mechanisms is key to the development of potential therapeutic targets for human imprinting disorders.

Epigenetic mosaicism and cell burden in Beckwith-Wiedemann Syndrome due to loss of methylation at imprinting control region 2

Beckwith–Wiedemann syndrome (BWS) is a rare overgrowth disorder caused by epigenetic alterations on Chromosome 11p15.5. Most molecular changes are sporadic and are thought to occur in a mosaic pattern. Thereby, the distribution of affected cells differs between tissues for each individual, which can complicate genotype–phenotype correlations. In two of the BWS molecular subtypes, tissue mosaicism has been demonstrated; however, mosaicism has not been specifically studied in the most common cause of BWS, loss of methylation (LOM) at KCNQ1OT1:TSS differentially methylated region (DMR) imprinting center 2 (IC2) LOM. The increased prevalence of twinning associated with the IC2 LOM subtype and the discordant phenotypes between the twins previously led to the proposal of diffused epigenetic mosaicism, leading to asymmetric distribution of affected cells during embryonic development. In this study, we evaluated the level of methylation detected in 64 samples collected from 30 individuals with IC2 LOM. We demonstrate that the IC2 LOM defect can occur in mosaic and nonmosaic patterns, and tissues from the same individual can show variable patterns, which suggests that this asymmetric distribution occurs during development. We further suggest that the clinical phenotype in individuals with BWS IC2 LOM is correlated with the epigenetic burden of affected cells in each tissue type. This series is the first report to demonstrate tissue mosaicism within the IC2 LOM epigenotype, and consideration of this mosaicism is necessary to understanding the pathogenesis of BWS.

Prospective study of epigenetic alterations responsible for isolated hemihyperplasia/hemihypoplasia and their association with leg length discrepancy

Background

Hemihyperplasia and hemihypoplasia result in leg length discrepancy (LLD) by causing skeletal asymmetry. Beckwith–Wiedemann syndrome (BWS) and Silver–Russell syndrome (SRS) are opposite growth-affecting disorders caused by opposite epigenetic alterations at the same chromosomal locus, 11p15, to induce hemihyperplasia and hemihypoplasia, respectively. Because of their somatic mosaicism, BWS and SRS show a wide spectrum of clinical phenotypes. We evaluated the underlying epigenetic alterations and potential epigenotype-phenotype correlations, focusing on LLD, in a group of individuals with isolated hemihyperplasia/hemihypoplasia.

Results

We prospectively collected paired blood-tissue samples from 30 patients with isolated hemihyperplasia/hemihypoplasia who underwent surgery for LLD. Methylation-specific multiplex-ligation-dependent probe amplification assay (MS-MLPA) and bisulfite pyrosequencing for differentially methylated regions 1 and 2 (DMR1 and DMR2) on chromosome 11p15 were performed using the patient samples. Samples from patients showing no abnormalities in MS-MLPA or bisulfite pyrosequencing were analyzed by single nucleotide polymorphism (SNP) microarray and CDKN1C Sanger sequencing. We introduced a metric named as the methylation difference, defined as the difference in DNA methylation levels between DMR1 and DMR2. The correlation between the methylation difference and the predicted LLD at skeletal maturity, calculated using a multiplier method, was evaluated. Predicted LLD was standardized for stature. Ten patients (33%) showed epigenetic alterations in MS-MLPA and bisulfite pyrosequencing. Of these, six and four patients had epigenetic alterations related to BWS and SRS, respectively. The clinical diagnosis of hemihyperplasia/hemihypoplasia was not compatible with the epigenetic alterations in four of these ten patients. No patients showed abnormalities in SNP array or their CDKN1C sequences. The standardized predicted LLD was moderately correlated with the methylation difference using fat tissue (r = 0.53; p = 0.002) and skin tissue (r = 0.50; p = 0.005) in all patients.

Conclusions

Isolated hemihyperplasia and hemihypoplasia can occur as a spectrum of BWS and SRS. Although the accurate differentiation between isolated hemihyperplasia and isolated hemihypoplasia is important in tumor surveillance planning, it is often difficult to clinically differentiate these two diseases without epigenetic tests. Epigenetic tests may play a role in the prediction of LLD, which would aid in treatment planning.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02042-6.

Temple syndrome and Kagami-Ogata syndrome: clinical presentations, genotypes, models and mechanisms

Temple syndrome (TS) and Kagami-Ogata syndrome (KOS) are imprinting disorders caused by absence or overexpression of genes within a single imprinted cluster on human chromosome 14q32. TS most frequently arises from maternal UPD14 or epimutations/deletions on the paternal chromosome, whereas KOS most frequently arises from paternal UPD14 or epimutations/deletions on the maternal chromosome. In this review, we describe the clinical symptoms and genetic/epigenetic features of this imprinted region. The locus encompasses paternally expressed protein-coding genes (DLK1, RTL1 and DIO3) and maternally expressed lncRNAs (MEG3/GTL2, RTL1as and MEG8), as well as numerous miRNAs and snoRNAs. Control of expression is complex, with three differentially methylated regions regulating germline, placental and tissue-specific transcription. The strong conserved synteny between mouse chromosome 12aF1 and human chromosome 14q32 has enabled the use of mouse models to elucidate imprinting mechanisms and decipher the contribution of genes to the symptoms of TS and KOS. In this review, we describe relevant mouse models and highlight their value to better inform treatment options for long-term management of TS and KOS patients.

Imaging for Staging of Pediatric Abdominal Tumors: An Update, From the AJR Special Series on Cancer Staging

The three most common pediatric solid tumors of the abdomen are neuroblastoma, Wilms tumor, and hepatoblastoma. These embryonal tumors most commonly present in the first decade of life. Each tumor has unique imaging findings, including locoregional presentation and patterns of distant spread. Neuroblastoma, Wilms tumor, and hepatoblastoma have unique staging systems that rely heavily on imaging and influence surgical and oncologic management. The staging systems include image-defined risk factors for neuroblastoma, the Children's Oncology Group staging system for Wilms tumor, and the pretreatment extent of tumor system (PRETEXT) for hepatoblastoma. It is important for radiologists to be aware of these staging systems to optimize image acquisition and interpretation. This article provides a practical and clinically oriented approach to the role of imaging in the staging of these common embryonal tumors of childhood. The selection among imaging modalities, key findings for determining tumor stage, and the role of imaging in posttreatment response evaluation and surveil-lance are discussed. Recent updates to the relevant staging systems are highlighted with attention to imaging findings of particular prognostic importance. The information presented will help radiologists tailor the imaging approach to the individual patient and guide optimal oncologic management.

The role of CTCF in the organization of the centromeric 11p15 imprinted domain interactome

DNA methylation, chromatin-binding proteins, and DNA looping are common components regulating genomic imprinting which leads to parent-specific monoallelic gene expression. Loss of methylation (LOM) at the human imprinting center 2 (IC2) on chromosome 11p15 is the most common cause of the imprinting overgrowth disorder Beckwith-Wiedemann Syndrome (BWS). Here, we report a familial transmission of a 7.6 kB deletion that ablates the core promoter of KCNQ1. This structural alteration leads to IC2 LOM and causes recurrent BWS. We find that occupancy of the chromatin organizer CTCF is disrupted proximal to the deletion, which causes chromatin architecture changes both in cis and in trans. We also profile the chromatin architecture of IC2 in patients with sporadic BWS caused by isolated LOM to identify conserved features of IC2 regulatory disruption. A strong interaction between CTCF sites around KCNQ1 and CDKN1C likely drive their expression on the maternal allele, while a weaker interaction involving the imprinting control region element may impede this connection and mediate gene silencing on the paternal allele. We present an imprinting model in which KCNQ1 transcription is necessary for appropriate CTCF binding and a novel chromatin conformation to drive allele-specific gene expression.

Isolated- and Beckwith-Wiedemann syndrome related- lateralised overgrowth (hemihypertrophy): Clinical and molecular correlations in 94 individuals

The congenital imprinting disorder, Beckwith-Wiedemann syndrome (BWS) is associated with variable clinical features including hemihypertrophy/lateralised overgrowth (LO) and embryonal tumour predisposition. BWS-associated (epi)genetic alterations occur in a subset of patients with isolated LO (ILO), leading to the concept of BWS spectrum disorder (BWSp). We investigated the relationship between clinical features and molecular diagnostic results in a cohort with LO using the BWSp international consensus group (BWSICG) clinical scoring system. Clinical/molecular findings in 94 previously-unreported patients with LO referred for BWSp molecular studies were reviewed retrospectively. The BWSICG score was assigned and diagnostic rate calculated. BWSp-associated (epi)genetic alteration was identified in 15/94 (16%). The molecular diagnostic rate by MS-MLPA (blood DNA) for BWS-related molecular findings in patients with LO was positively correlated with the BWSICG score. 3/48 with ILO had a molecular alteration. No individuals with ILO had developed an embryonal tumour at last follow up. Among a cohort of individuals with LO referred for BWSp molecular testing, the BWSICG score correlated with diagnostic yield. The embryonal tumour risk in children with ILO and negative molecular testing appeared very low, however longer- and more complete follow up is required to better define tumour risks in this group.

Phenotypically concordant but epigenetically discordant monozygotic dichorionic diamniotic twins with Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder caused by (epi)genetic alterations. The incidence of monozygotic (MZ) twins in BWS is higher than in the general population. Most MZ twins with BWS are female and have phenotypical discordance: one twin is clinically diagnosed with BWS, while the other shows a mild or normal phenotype. The most frequent (epi)genetic alteration in MZ twins is loss of methylation of imprinting control region 2 (ICR2-LOM) at 11p15.5. Intriguingly, ICR2-LOM is usually found in the peripheral blood leukocytes (PBL) of both twins, even if they are clinically discordant. Here, we present a rare pair of MZ dichorionic diamniotic female twins with BWS and concordant phenotypes (a Beckwith-Wiedemann spectrum score of 5 in each twin). Molecular analysis of genomic DNA from PBL revealed ICR2-LOM in one twin but not the other. Our analyses suggest that ICR2-LOM occurred between days 1 and 3 after fertilization, followed by twinning. We speculate that during embryogenesis, ICR2-LOM cells were distributed to the hematopoietic stem cells in different ratios in the two fetuses, and also to commonly affected tissues, such as the tongue, in similar ratios, although we were unable to analyze any tissues other than PBL.

Prenatal molecular testing and diagnosis of Beckwith-Wiedemann syndrome

OBJECTIVE

The objective of this study was to describe molecular findings and phenotypic features among individuals referred for prenatal Beckwith-Wiedemann syndrome (BWS) testing.

METHODS

Molecular diagnostic testing was performed using a sensitive quantitative real-time PCR-based assay capable of detecting mosaic methylation to the level of 3% at IC1 and IC2. Sanger sequencing of CDKN1C was performed in cases with normal methylation.

RESULTS

Of the 94 patients tested, a molecular diagnosis was identified for 25.5% of cases; 70.9% of diagnosed cases had loss of methylation at IC2, 4.2% had gain of methylation at IC1, 12.5% had paternal uniparental isodisomy, and 12.5% had CDKN1C loss-of-function variants. Methylation level changes in prenatal cases were significantly greater than changes identified in cases tested after birth. Cases with a prenatal molecular diagnosis had a significantly greater number of BWS-associated phenotypic features. The presence of either macroglossia or placentomegaly was most predictive of a BWS diagnosis.

CONCLUSION

Our results support the consensus statement advocating BWS molecular testing for all patients with one or more BWS-associated prenatal features and suggest that low-level mosaic methylation changes may be uncommon among prenatal BWS diagnoses.

Pediatric Cushing syndrome: An early sign of an underling cancer predisposition syndrome

Beckwith-Wiedemann syndrome (BWS) is a genetic overgrowth and cancer predisposition syndrome that can be associated with a spectrum of clinical features including isolated lateralized overgrowth, macrosomia, macroglossia, organomegaly, omphalocele/umbilical hernia, and distinct facial features. Because of a range of clinical presentations and molecular defects involving Chromosome 11p15, many cases will fall within what is now being defined as the Beckwith-Wiedemann spectrum (BWSp). Cushing syndrome (CS) in infants is a rare neuroendocrinological disease associated with hypercortisolism that has rarely been reported in patients with BWS. Here, we describe the first case of a 5-month-old male with CS secondary to paternal uniparental disomy of Chromosome 11p without additional clinical signs or symptoms of BWS. This case continues to expand the phenotypic spectrum of BWSp.

The number of the CTCF binding sites of the H19/IGF2:IG-DMR correlates with DNA methylation and expression imprinting in a humanized mouse model

The reciprocal parent of origin-specific expression of H19 and IGF2 is controlled by the H19/IGF2:IG-DMR (IC1), whose maternal allele is unmethylated and acts as a CTCF-dependent insulator. In humans, internal IC1 deletions are associated with Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS), depending on their parental origin. These genetic mutations result in aberrant DNA methylation, deregulation of IGF2/H19 and disease with incomplete penetrance. However, the mechanism linking the microdeletions to altered molecular and clinical phenotypes remains unclear. To address this issue, we have previously generated and characterized two knock-in mouse lines with the human wild-type (hIC1wt) or mutant (hIC1∆2.2) IC1 allele replacing the endogenous mouse IC1 (mIC1). Here, we report an additional knock-in line carrying a mutant hIC1 allele with an internal 1.8 kb deletion (hIC1∆1.8). The phenotype of these mice is different from that of the hIC1∆2.2-carrying mice, partially resembling hIC1wt animals. Indeed, proper H19 and Igf2 imprinting and normal growth phenotype were evident in the mice with maternal transmission of hIC1Δ1.8, while low DNA methylation and non-viable phenotype characterize its paternal transmission. In contrast to hIC1wt, E15.5 embryos that paternally inherit hIC1Δ1.8 displayed variegated hIC1 methylation. In addition, increased Igf2 expression, correlating with increased body weight, was found in one third of these mice. Chromatin immunoprecipitation experiments in mouse embryonic stem cells carrying the three different hIC1 alleles demonstrate that the number of CTCF target sites influences its binding to hIC1, indicating that in the mouse, CTCF binding is key to determining hIC1 methylation and Igf2 expression.

Clinical and Molecular Diagnosis of Beckwith-Wiedemann Syndrome with Single- or Multi-Locus Imprinting Disturbance

Beckwith-Wiedemann syndrome (BWS) is a clinically and genetically heterogeneous overgrowth disease. BWS is caused by (epi)genetic defects at the 11p15 chromosomal region, which harbors two clusters of imprinted genes, IGF2/H19 and CDKN1C/KCNQ1OT1, regulated by differential methylation of imprinting control regions, H19/IGF2:IG DMR and KCNQ1OT1:TSS DMR, respectively. A subset of BWS patients show multi-locus imprinting disturbances (MLID), with methylation defects extended to other imprinted genes in addition to the disease-specific locus. Specific (epi)genotype-phenotype correlations have been defined in order to help clinicians in the classification of patients and referring them to a timely diagnosis and a tailored follow-up. However, specific phenotypic correlations have not been identified among MLID patients, thus causing a debate on the usefulness of multi-locus testing in clinical diagnosis. Finally, the high incidence of BWS monozygotic twins with discordant phenotypes, the high frequency of BWS among babies conceived by assisted reproductive technologies, and the female prevalence among BWS-MLID cases provide new insights into the timing of imprint establishment during embryo development. In this review, we provide an overview on the clinical and molecular diagnosis of single- and multi-locus BWS in pre- and post-natal settings, and a comprehensive analysis of the literature in order to define possible (epi)genotype-phenotype correlations in MLID patients.

Familial Beckwith-Wiedemann syndrome: Prenatal manifestation and a possible expansion of the phenotype

We describe a case of Beckwith-Wiedemann syndrome (BWS) demonstrating pre- and post-natal intra-familial variability. Our first encounter with the family occurred in the 1990s following the birth of 3 affected offspring. The first two pregnancies presented with exomphalos and elevated second trimester maternal serum alpha-fetoprotein (msAFP, 3.43 and 4.01 MOM, respectively) as well as elevated maternal human chorionic gonadotrophin (mhCG, 4.33 and 8.8 MOM, respectively). The diagnosis of BWS was confirmed postnatally in both cases. The third ongoing pregnancy presented only with elevated mhCG (7.09 MOM) and no malformation. Nonetheless BWS was suspected. The diagnosis was confirmed postnatally with clinical manifestations including macroglossia and cleft palate. Two affected female siblings were also diagnosed with Mullerian agenesis in adulthood. Suspecting a common genetic etiology, sequencing of the CDKN1C gene revealed a maternally inherited, likely pathogenic variant (NM_000076.2: c.367_385del; p.(Ala123Serfs*143)) causative of BWS. Chromosomal microarray and whole exome sequencing did not reveal any other pathogenic variant that would explain the Mullerian agenesis. One of the affected females underwent successful preimplantation genetic testing (PGT) with a surrogate and gave birth to a healthy female. To the best of our knowledge, this is the first report of Mullerian agenesis as a possible rare expansion of the BWS phenotype. In addition, this case highlights the potential role of abnormal second trimester biochemical markers (msAFP, mHCG) as possible indicators of BWS, especially in familial cases.