Wiedemann-Steiner syndrome: Novel pathogenic variant and review of literature

Diagnosis and initial management of children presenting with premature loss of primary teeth associated with a systemic condition: A scoping review and development of clinical aid

BACKGROUND

Premature loss of primary teeth (PLPT) can be a rare presentation of systemic medical conditions. Premature loss of primary teeth may present a diagnostic dilemma to paediatric dentists.

AIMS

To identify systemic conditions associated with PLPT and develop a clinical aid.

DESIGN

OVID Medline, Embase and Web of Science were searched up to March 2023. Citation searching of review publications occurred. Exclusion occurred for conference abstracts, absence of PLPT and absence of English-language full text.

RESULTS

Seven hundred and ninety-one publications were identified via databases and 476 by citation searching of review articles. Removal of 390 duplicates occurred. Following the exclusion of 466 records on abstract review, 411 publications were sought for retrieval, of which 142 met inclusion criteria. Thirty-one systemic conditions were identified. For 19 conditions, only one publication was identified. The majority of publications, 91% (n = 129), were case reports or series. Most publications, 44% (n = 62), were related to hypophosphatasia, and 25% (n = 35) were related to Papillon-Lefèvre. Diagnostic features were synthesised, and a clinical aid was produced by an iterative consensus approach.

CONCLUSIONS

A diverse range of systemic diseases are associated with PLPT. Evidence quality, however, is low, with most diseases having a low number of supporting cases. This clinical aid supports paediatric dentists in differential diagnosis and onward referral.

The social phenotype associated with Wiedemann-Steiner syndrome: Autistic traits juxtaposed with high social drive and prosociality

The aim of this study was to provide a descriptive overview of the social characteristics associated with Wiedemann-Steiner syndrome (WSS). A total of 24 parents of children/adults with WSS (11F, mean age = 12.94 years, SD = 8.00) completed the Social Responsiveness Scale 2nd Edition (SRS-2); Colorado Learning Difficulties Questionnaire (CLDQ) and Strengths and Difficulties Questionnaire (SDQ). Almost half our sample reported a diagnosis of autism spectrum disorder (ASD) and 70% had intellectual disability. On the SDQ, over 90% of participants were rated in borderline/clinical ranges in Peer Problems, yet the majority fell within normal limits in Prosocial Behaviors. Most fell in the moderate/severe difficulties ranges across SRS-2 Social Cognition, Communication, and Restricted/Repetitive Behaviors scales (all >70%); whereas substantially less participants met these ranges for deficits in Social Awareness (50%) and Social Motivation (33.33%). A pattern of relatively strong prosocial skills and social drive in the context of difficulties with inflexible behaviors, social cognition, and communication was observed, regardless of gender, ASD or intellectual disability diagnosis. The social phenotype associated with WSS is characterized by some autistic features paired with unusually high social motivation and prosocial tendencies.

A de novo mutation of ADAMTS8 in a patient with Wiedemann-Steiner syndrome

BACKGROUND

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant disorder caused by mutations in the KMT2A gene and is usually characterized by hairy elbows, short stature, developmental delay, intellectual disability and obvious facial dysmorphism.

CASE PRESENTATION

Here, we report a 5-year-old girl with clinical features similar to WDSTS, including postnatal growth delay, retarded intellectual development, and ocular hypertelorism. Through whole-exome sequencing (WES), a frameshift variant of KMT2A was found in the patient but not in her parents' genomic DNA. By bioinformatics analysis, the KMT2A variant was demonstrated to be the top candidate pathogenic variant for the clinical phenotype consistent with WDSTS. Moreover, a duplication of exon 1 in ADAMTS8 (belonging to the zinc metalloproteinase family) was found in the genomic DNA of this patient, which may be responsible for the characteristics that are different from those of WDSTS, including early teething, rapid tooth replacement, and dysplastic enamel.

CONCLUSIONS

From the above results, we propose that in our patient, the frameshift variant in KMT2A is the main reason for the WDSTS phenotype, and the unreported mutation in ADAMTS8 may be the candidate reason for other characteristics that are different from those of WDSTS. Therefore, this study not only provides a new KMT2A variant associated with WDSTS but is also a reminder that combined mutations may be present in a case with more characteristics than those seen in WDSTS.

Novel variants and phenotypic heterogeneity in a cohort of 11 Chinese children with Wiedemann-Steiner syndrome

Objective: Wiedemann-Steiner syndrome (WSS) is a rare autosomal dominant disorder caused by deleterious heterozygous variants of the KMT2A gene. This study aims to describe the phenotypic and genotypic features of Chinese WSS patients, and assess therapeutic effects of recombinant human growth hormone (rhGH). Methods: Eleven Chinese children with WSS were enrolled in our cohort. Their clinical, imaging, biochemical and molecular findings were analyzed retrospectively. Moreover, the phenotypic features of 41 previously reported Chinese WSS patients were reviewed and included in our analysis. Results: In our cohort, the 11 WSS patients presented with classic clinical manifestations, but with different frequencies. The most common clinical features were short stature (90.9%) and developmental delay (90.9%), followed by intellectual disability (72.7%). The most frequent imaging features were patent ductus arteriosus (57.1%) and patent foramen ovale (42.9%) in cardiovascular system, and abnormal corpus callosum (50.0%) in the brain. In the set comprising 52 Chinese WSS patients, the most common clinical and imaging manifestations were developmental delay (84.6%), intellectual disability (84.6%), short stature (80.8%) and delayed bone age (68.0%), respectively. Eleven different variants, including three known and eight novel variants, of the KMT2A gene were identified in our 11 WSS patients without a hotspot variant. Two patients were treated with rhGH and yielded satisfactory height gains, but one developed acceleration of bone age. Conclusion: Our study adds 11 new patients with WSS, reveals different clinical characteristics in Chinese WSS patients, and extends the mutational spectrum of the KMT2A gene. Our study also shares the therapeutic effects of rhGH in two WSS patients without GH deficiency.

Anxiety in Wiedemann-Steiner syndrome

This study examined anxiety in Wiedemann-Steiner syndrome (WSS). Eighteen caregivers and participants with WSS completed the parent- and self-report versions of the Screen for Child Anxiety Related Disorder or the adapted version of the Screen for Adult Anxiety Related Disorder. Approximately 33.33% of parents and 65% of participants with WSS rated in the clinical range for overall anxiety. Across anxiety subtypes, parents primarily indicated concerns with Separation Anxiety (72%), which was also endorsed by the majority of participants with WSS (82%). The emergent trend showed Total Anxiety increased with age based on parent-informant ratings. The behavioral phenotype of WSS includes elevated anxiety. Clinical management should include incorporating early behavioral interventions to bolster emotion regulation given the observed risk of anxiety with age.

Phenotypic Variation in Two Siblings Affected with Shwachman-Diamond Syndrome: The Use of Expert Variant Interpreter (eVai) Suggests Clinical Relevance of a Variant in the KMT2A Gene

Introduction. Shwachman-Diamond Syndrome (SDS) is an autosomal-recessive disorder characterized by neutropenia, pancreatic exocrine insufficiency, skeletal dysplasia, and an increased risk for leukemic transformation. Biallelic mutations in the SBDS gene have been found in about 90% of patients. The clinical spectrum of SDS in patients is wide, and variability has been noticed between different patients, siblings, and even within the same patient over time. Herein, we present two SDS siblings (UPN42 and UPN43) carrying the same SBDS mutations and showing relevant differences in their phenotypic presentation. Study aim. We attempted to understand whether other germline variants, in addition to SBDS, could explain some of the clinical variability noticed between the siblings. Methods. Whole-exome sequencing (WES) was performed. Human Phenotype Ontology (HPO) terms were defined for each patient, and the WES data were analyzed using the eVai and DIVAs platforms. Results. In UPN43, we found and confirmed, using Sanger sequencing, a novel de novo variant (c.10663G > A, p.Gly3555Ser) in the KMT2A gene that is associated with autosomal-dominant Wiedemann−Steiner Syndrome. The variant is classified as pathogenic according to different in silico prediction tools. Interestingly, it was found to be related to some of the HPO terms that describe UPN43. Conclusions. We postulate that the KMT2A variant found in UPN43 has a concomitant and co-occurring clinical effect, in addition to SBDS mutation. This dual molecular effect, supported by in silico prediction, could help to understand some of the clinical variations found among the siblings. In the future, these new data are likely to be useful for personalized medicine and therapy for selected cases.

KMT2A: Umbrella Gene for Multiple Diseases

KMT2A (Lysine methyltransferase 2A) is a member of the epigenetic machinery, encoding a lysine methyltransferase responsible for the transcriptional activation through lysine 4 of histone 3 (H3K4) methylation. KMT2A has a crucial role in gene expression, thus it is associated to pathological conditions when found mutated. KMT2A germinal mutations are associated to Wiedemann–Steiner syndrome and also in patients with initial clinical diagnosis of several other chromatinopathies (i.e., Coffin–Siris syndromes, Kabuki syndrome, Cornelia De Lange syndrome, Rubinstein–Taybi syndrome), sharing an overlapping phenotype. On the other hand, KMT2A somatic mutations have been reported in several tumors, mainly blood malignancies. Due to its evolutionary conservation, the role of KMT2A in embryonic development, hematopoiesis and neurodevelopment has been explored in different animal models, and in recent decades, epigenetic treatments for disorders linked to KMT2A dysfunction have been extensively investigated. To note, pharmaceutical compounds acting on tumors characterized by KMT2A mutations have been formulated, and even nutritional interventions for chromatinopathies have become the object of study due to the role of microbiota in epigenetic regulation.

Clinical Utility of a Unique Genome-Wide DNA Methylation Signature for KMT2A-Related Syndrome

Wiedemann–Steiner syndrome (WDSTS) is a Mendelian syndromic intellectual disability (ID) condition associated with hypertrichosis cubiti, short stature, and characteristic facies caused by pathogenic variants in the KMT2A gene. Clinical features can be inconclusive in mild and unusual WDSTS presentations with variable ID (mild to severe), facies (typical or not) and other associated malformations (bone, cerebral, renal, cardiac and ophthalmological anomalies). Interpretation and classification of rare KMT2A variants can be challenging. A genome-wide DNA methylation episignature for KMT2A-related syndrome could allow functional classification of variants and provide insights into the pathophysiology of WDSTS. Therefore, we assessed genome-wide DNA methylation profiles in a cohort of 60 patients with clinical diagnosis for WDSTS or Kabuki and identified a unique highly sensitive and specific DNA methylation episignature as a molecular biomarker of WDSTS. WDSTS episignature enabled classification of variants of uncertain significance in the KMT2A gene as well as confirmation of diagnosis in patients with clinical presentation of WDSTS without known genetic variants. The changes in the methylation profile resulting from KMT2A mutations involve global reduction in methylation in various genes, including homeobox gene promoters. These findings provide novel insights into the molecular etiology of WDSTS and explain the broad phenotypic spectrum of the disease.

Severe Hip Dysplasia in Wiedemann-Steiner Syndrome Treated with Bilateral Bernese Periacetabular Osteotomy: A Case Report

CASE

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant disorder with many phenotypic characteristics, including multiple orthopaedic manifestations. Of these, symptomatic significant hip dysplasia has been variably noted. Nonetheless, few reports detail surgical treatment for these patients, including hip preservation for those with hip dysplasia.

CONCLUSION

Periacetabular osteotomy allows for the correction of severe hip dysplasia in patients with WDSTS. With proper recognition and timely intervention, adequate care may be provided for these patients.

Case report: 11-ketotestosterone may potentiate advanced bone age as seen in some cases of Wiedemann-Steiner Syndrome

CONTEXT

Wiedemann-Steiner Syndrome (WSS) is a genetic disorder associated with an array of clinical phenotypes, including advanced bone age and short stature. 11-ketotestosterone (11KT) is a member of the group known as 11-oxygenated C19 androgens that are implicated in premature adrenarche.

CASE DESCRIPTION

Case 1: The patient is a 3 year and 11-month-old female diagnosed with WSS due to deletion of KMT2A detected on CGH microarray. At two years and 11 months, imaging revealed an advanced bone age. We obtained an 11KT level on this patient. 11KT in case 1 was elevated at 26.3 ng/dL, while the normal reference range is 7.3-10.9 ng/dL and the reference interval for premature adrenarche is 12.3-22.9 ng/dL, The repeat 11KT at follow up (chronological age 4 years and 6 months) was still elevated at 33.8 ng/dL Case 2: A second child with WSS and a 5kb intragenic KMT2A deletion was evaluated at 11 months of age; his 11KT was 4.5 ng/dL.

CONCLUSIONS

The elevated 11KT may indicate maturational changes related to increasing adrenal gland androgenic activation and may explain the advanced bone age seen in some patients with WSS. To our knowledge, this is the first case report that describes 11KT as a bioactive androgen potentially causing bone age advancement in WSS. Lack of elevation of 11KT in the second child who is an infant suggests increasing androgenic precursors and metabolites related to premature adrenarche may need to be longitudinally followed.

Sleep disturbances correlate with behavioral problems among individuals with Wiedemann-Steiner syndrome

Wiedemann-Steiner syndrome (WSS) is a rare genetic disorder caused by mutation in KMT2A and characterized by neurodevelopmental delay. This study is the first prospective investigation to examine the sleep and behavioral phenotypes among those with WSS through parent-informant screening inventories. A total of 24 parents of children/adults with WSS (11F, Mean age = 12.71 years, SD = 8.17) completed the Strengths and Difficulties Questionnaire (SDQ) and 22 of these caregivers also completed the Modified Simonds and Parraga Sleep Questionnaire (MSPSQ). On average, the majority of those with WSS (83%) were rated to show borderline to clinical level of behavioral difficulties on the SDQ. Approximately 83% were rated in these ranges for hyperactivity, 63% for emotional problems, and 50% for conduct problems. When applying prior published clinical cut-off for risk of sleep disturbance among those with neurodevelopmental disorders, over 80% of our sample exceeded this limit on the MSPSQ. Largely, caregivers' ratings suggested restless sleep, rigid bedtime rituals, sleep reluctance and breathing through the mouth in sleep were most consistent problems observed. Partial correlations between sleep and behavioral domains showed elevated emotional problems were associated with parasomnia characteristics after controlling for age. Daytime drowsiness and activity were associated with more hyperactivity. Those with more night waking problems and delayed sleep onset were rated to show more severe conduct problems. Overall, these findings suggest dysfunctional sleep behaviors, hyperactivity, and affective problems are part of the neurobehavioral phenotype of WSS. Routine clinical care for those affected by WSS should include close monitoring of sleep and overactive behaviors.

Wiedemann–Steiner Syndrome with a Pathogenic Variant in KMT2A from Taiwan

Wiedemann–Steiner syndrome (WSS) is a rare genetic disorder. Patients with WSS have characteristics of growth retardation, facial dysmorphism, hypertrichosis cubiti (HC), and neurodevelopmental delays. WSS is in an autosomal dominant inherited pattern caused by a mutation of the KMT2A gene (NM_001197104.2). In this article, we discuss a 5-year-old boy who has mild intellectual disability (ID), hypotonia, HC, hypertrichosis on the back, dysmorphic facies, psychomotor retardation, and growth delay. Trio-based whole-exome sequencing (trio-WES) was carried out on this patient and his parents, confirming the variants with Sanger sequencing. Trio-WES showed a de novo mutation of the KMT2A gene (NM_001197104.2: c.4696G>A, p.Gly1566Arg). On the basis of the clinical features and the results of the WES, WSS was diagnosed. Therefore, medical professionals should consider a diagnosis of WSS if patients have growth retardation and development delay as well as hirsutism, particularly HC.

Expanding the genotypic and phenotypic spectrum in a diverse cohort of 104 individuals with Wiedemann-Steiner syndrome

Wiedemann-Steiner syndrome (WSS) is an autosomal dominant disorder caused by monoallelic variants in KMT2A and characterized by intellectual disability and hypertrichosis. We performed a retrospective, multicenter, observational study of 104 individuals with WSS from five continents to characterize the clinical and molecular spectrum of WSS in diverse populations, to identify physical features that may be more prevalent in White versus Black Indigenous People of Color individuals, to delineate genotype-phenotype correlations, to define developmental milestones, to describe the syndrome through adulthood, and to examine clinicians' differential diagnoses. Sixty-nine of the 82 variants (84%) observed in the study were not previously reported in the literature. Common clinical features identified in the cohort included: developmental delay or intellectual disability (97%), constipation (63.8%), failure to thrive (67.7%), feeding difficulties (66.3%), hypertrichosis cubiti (57%), short stature (57.8%), and vertebral anomalies (46.9%). The median ages at walking and first words were 20 months and 18 months, respectively. Hypotonia was associated with loss of function (LoF) variants, and seizures were associated with non-LoF variants. This study identifies genotype-phenotype correlations as well as race-facial feature associations in an ethnically diverse cohort, and accurately defines developmental trajectories, medical comorbidities, and long-term outcomes in individuals with WSS.

Wiedemann-Steiner syndrome: A case report

Wiedemann-Steiner syndrome (WDSTS) is an exceptionally rare autosomal dominant syndrome with considerable phenotypical variation. Clinical features include dysmorphic facial and skeletal features, growth deficiency, developmental delay, hypertrichosis cubiti and various dental features. We present a 7-year-old female with premature exfoliation of primary teeth and premature eruption of permanent teeth.

Wiedemann-Steiner Syndrome as a Differential Diagnosis of Cornelia de Lange Syndrome Using Targeted Next-Generation Sequencing: A Case Report

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant disorder with a variable clinical phenotype including synophrys, hypertelorism, thick eyebrows, long eyelashes, wide nasal bridge, long philtrum, hypertrichosis, growth retardation, and intellectual disability. Cornelia de Lange syndrome (CdLS) is a rare disease characterized by synophrys, long eyelashes, limb abnormalities, generalized hirsutism, growth retardation, and intellectual disability. In both WDSTS and CdLS, the malformations are due to transcriptome disturbance caused by defects in the genes encoding the components of chromatin regulation and transcription process. The overlapping features in these two syndromes may complicate the original diagnosis of a patient. Here, we report on a Wiedemann-Steiner patient found to have a de novo pathogenic KMT2A variation who had been clinically suspected as CdLS. We suggest that targeted next-generation sequencing is a feasible tool for the precise diagnosis of patients who have phenotypically and clinically overlapping features of CdLS and WDSTS.

Expanding the phenotype of Wiedemann-Steiner syndrome: Craniovertebral junction anomalies

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant condition caused by heterozygous loss of function variants in the KMT2A (MLL) gene, encoding a lysine N-methyltransferase that mediates a histone methylation pattern specific for epigenetic transcriptional activation. WDSTS is characterized by a distinctive facial phenotype, hypertrichosis, short stature, developmental delay, intellectual disability, congenital malformations, and skeletal anomalies. Recently, a few patients have been reported having abnormal skeletal development of the cervical spine. Here we describe 11 such individuals, all with KMT2A de novo loss-of-function variants: 10 showed craniovertebral junction anomalies, while an 11th patient had a cervical abnormality in C7. By evaluating clinical and diagnostic imaging data we characterized these anomalies, which consist primarily of fused cervical vertebrae, C1 and C2 abnormalities, small foramen magnum and Chiari malformation type I. Craniovertebral anomalies in WDSTS patients have been largely disregarded so far, but the increasing number of reports suggests that they may be an intrinsic feature of this syndrome. Specific investigation strategies should be considered for early identification and prevention of craniovertebral junction complications in WDSTS patients.

Wiedemann–Steiner Syndrome: A Rare Differential Diagnosis of Neurodevelopmental Delay and Dysmorphic Features

Wiedemann–Steiner syndrome (WSS) is a rare genetic disorder characterized by dysmorphic features, neurodevelopmental delay, growth retardation, and hypertrichosis cubiti. It is caused by pathogenic variants in the KMT2A gene. Here, we report a child with WSS presented with neurodevelopmental delay. Genetic analysis revealed a heterozygous c.2312dupC (p.Ser774Valfs*11) variant at the KMT2A gene that was classified as pathogenic in dbSNP (rs1057518649). To the best of our knowledge, this is the first patient of WSS from Turkey. This case draws attention to the diagnosis of WSS in children with neurodevelopmental delay.

Expanding the phenotype associated to KMT2A variants: overlapping clinical signs between Wiedemann-Steiner and Rubinstein-Taybi syndromes

Lysine-specific methyltransferase 2A (KMT2A) is responsible for methylation of histone H3 (K4H3me) and contributes to chromatin remodeling, acting as "writer" of the epigenetic machinery. Mutations in KMT2A were first reported in Wiedemann-Steiner syndrome (WDSTS). More recently, KMT2A variants have been described in probands with a specific clinical diagnosis comprised in the so-called chromatinopathies. Such conditions, including WDSTS, are a group of overlapping disorders caused by mutations in genes coding for the epigenetic machinery. Among them, Rubinstein-Taybi syndrome (RSTS) is mainly caused by heterozygous pathogenic variants in CREBBP or EP300. In this work, we used next generation sequencing (either by custom-made panel or by whole exome) to identify alternative causative genes in individuals with a RSTS-like phenotype negative to CREBBP and EP300 mutational screening. In six patients we identified different novel unreported variants in KMT2A gene. The identified variants are de novo in at least four out of six tested individuals and all of them display some typical RSTS phenotypic features but also WDSTS specific signs. This study reinforces the concept that germline variants affecting the epigenetic machinery lead to a shared molecular effect (alteration of the chromatin state) determining superimposable clinical conditions.

Physical Therapy Management of Wiedemann-Steiner Syndrome From Birth to 3 Years

PURPOSE

To investigate Wiedemann-Steiner syndrome (WSS), its correlation to hypotonia and developmental delay, and to determine the relative intervention strategies that may be useful during early intervention from birth to 3 years.

METHODS

A literature search using PEDro and PubMed was conducted using key words "Wiedemann-Steiner syndrome," "hypotonia," and "developmental delay" and a case study is presented.

RESULTS

A 36-month-old child with WSS received PT intervention beginning at 2 months old. Addition of orthotics and treadmill walking was added at 13 and 19 months, respectively. The child progressed through developmental sequences from rolling, sitting, standing, and walking although consistently scored with motor delay of -2 SD.

CONCLUSIONS

Fifty-seven percent of children diagnosed with WSS have hypotonia, and 90% have developmental delay. The diagnosis of WSS should require physical therapy services through early intervention programs due to its high correlation with motor developmental delay and disability. Determination of progress should be measured with achievement of function rather than norm-referenced outcome measures.Video Abstract: For more insights from the authors, access Supplemental Digital Content 1, available at: http://links.lww.com/PPT/A292.

Clinical and molecular spectrum of Wiedemann-Steiner syndrome, an emerging member of the chromatinopathy family

Wiedemann-Steiner syndrome (OMIM #605130) is a rare congenital malformation syndrome characterized by hypertrichosis cubiti associated with short stature; consistent facial features, including long eyelashes, thick or arched eyebrows with a lateral flare, wide nasal bridge, and downslanting and vertically narrow palpebral fissures; mild to moderate intellectual disability; behavioral difficulties; and hypertrichosis on the back. It is caused by heterozygous pathogenic variants in KMT2A. This gene has an established role in histone methylation, which explains the overlap of Wiedemann-Steiner syndrome with other chromatinopathies, a heterogeneous group of syndromic conditions that share a common trigger: The disruption of one of the genes involved in chromatin modification, leading to dysfunction of the epigenetic machinery.

Genetic Disorders in Prenatal Onset Syndromic Short Stature Identified by Exome Sequencing

OBJECTIVE

To perform a prospective genetic investigation using whole exome sequencing of a group of patients with syndromic short stature born small for gestational age of unknown cause.

STUDY DESIGN

For whole exome sequencing analysis, we selected 44 children born small for gestational age with persistent short stature, and additional features, such as dysmorphic face, major malformation, developmental delay, and/or intellectual disability. Seven patients had negative candidate gene testing based on clinical suspicion and 37 patients had syndromic conditions of unknown etiology.

RESULTS

Of the 44 patients, 15 (34%) had pathogenic/likely pathogenic variants in genes already associated with growth disturbance: COL2A1 (n = 2), SRCAP (n = 2), AFF4, ACTG1, ANKRD11, BCL11B, BRCA1, CDKN1C, GINS1, INPP5K, KIF11, KMT2A, and POC1A (n = 1 each). Most of the genes found to be deleterious participate in fundamental cellular processes, such as cell replication and DNA repair.

CONCLUSIONS

The rarity and heterogeneity of syndromic short stature make the clinical diagnosis difficult. Whole exome sequencing allows the diagnosis of previously undiagnosed patients with syndromic short stature.

Wiedemann-Steiner syndrome with a novel pathogenic variant in KMT2A: a case report

Case Description:

We report the case of a one-year-old girl who was diagnosed with Wiedemann-Steiner Syndrome based on the identification of a novel de novo frameshift mutation in the KMT2A gene by whole exome sequencing and supported by her clinical features.

Clinical Findings:

KMT2A mutations cause Wiedemann-Steiner Syndrome, a very rare genetic disorder characterized by congenital hypertrichosis, short stature, intellectual disability, and distinct facial features.

Treatment and Outcome:

Whole exome sequencing identified a novel frameshift variant: c. 4177dupA (p.Ile1393Asnfs * 14) in KMT2A; this change generates an alteration of the specific binding to non-methylated CpG motifs of the DNA to the protein. The genotype and phenotype of the patient were compared with those of earlier reported patients in the literature.

Clinical Relevance:

In diseases with low frequency, it is necessary to establish a genotype-phenotype correlation that allows the establishment of therapeutic and follow-up goals. The phenotype comparation with other reported cases did not show differences attributable to sex or age among patients with Wiedemann-Steiner Syndrome. Whole exome sequencing allows identifying causality in conditions with high clinical and genetic heterogeneity like hypertrichosis.

Exploring by whole exome sequencing patients with initial diagnosis of Rubinstein-Taybi syndrome: the interconnections of epigenetic machinery disorders

Rubinstein-Taybi syndrome (RSTS) is an autosomal-dominant neurodevelopmental disease affecting 1:125,000 newborns characterized by intellectual disability, growth retardation, facial dysmorphisms and skeletal abnormalities. RSTS is caused by mutations in genes encoding for writers of the epigenetic machinery: CREBBP (~ 60%) or its homologous EP300 (~ 10%). No causative mutation is identified in up to 30% of patients. We performed whole-exome sequencing (WES) on eight RSTS-like individuals who had normal high-resolution array CGH testing and were CREBBP- and EP300-mutation -negative, to identify the molecular cause. In four cases, we identified putatively causal variants in three genes (ASXL1, KMT2D and KMT2A) encoding members of the epigenetic machinery known to be associated with the Bohring-Opitz, Kabuki and Wiedemann-Steiner syndromes. Each variant is novel, de novo, fulfills the ACMG criteria and is predicted to result in loss-of-function leading to haploinsufficiency of the epi-gene. In two of the remaining cases, homozygous/compound heterozygous variants in XYLT2 and PLCB4 genes, respectively, associated with spondyloocular and auriculocondylar 2 syndromes and in the latter an additional candidate variant in XRN2, a gene yet unrelated to any disease, were detected, but their pathogenicity remains uncertain. These results underscore the broad clinical spectrum of Mendelian disorders of the epigenetic apparatus and the high rate of WES disclosure of the genetic basis in cases which may pose a challenge for phenotype encompassing distinct syndromes. The overlapping features of distinct intellectual disability syndromes reflect common pathogenic molecular mechanisms affecting the complex regulation of balance between open and closed chromatin.

The progression of Wiedemann-Steiner syndrome in adulthood and two novel variants in the KMT2A gene

Wiedemann-Steiner syndrome is a genetic condition associated with dysmorphic facies, hypertrichosis, short stature, developmental delay, and intellectual disability. Congenital malformations of the cerebral, cardiac, renal, and optic structures have also been reported. Because the majority of reported individuals with this condition have been under age 20, the long-term prognosis is not well defined. Here we report on two further unrelated individuals diagnosed with Wiedemann-Steiner syndrome, one of whom is in her third decade of life. In addition, both individuals have novel KMT2A mutations. The information provided below about the outcome in Wiedemann-Steiner syndrome is important for families of affected individuals.

RNA Sequencing and Pathway Analysis Identify Important Pathways Involved in Hypertrichosis and Intellectual Disability in Patients with Wiedemann-Steiner Syndrome

A growing number of histone modifiers are involved in human neurodevelopmental disorders, suggesting that proper regulation of chromatin state is essential for the development of the central nervous system. Among them, heterozygous de novo variants in KMT2A, a gene coding for histone methyltransferase, have been associated with Wiedemann-Steiner syndrome (WSS), a rare developmental disorder mainly characterized by intellectual disability (ID) and hypertrichosis. As KMT2A is known to regulate the expression of multiple target genes through methylation of lysine 4 of histone 3 (H3K4me), we sought to investigate the transcriptomic consequences of KMT2A variants involved in WSS. Using fibroblasts from four WSS patients harboring loss-of-function KMT2A variants, we performed RNA sequencing and identified a number of genes for which transcription was altered in KMT2A-mutated cells compared to the control ones. Strikingly, analysis of the pathways and biological functions significantly deregulated between patients with WSS and healthy individuals revealed a number of processes predicted to be altered that are relevant for hypertrichosis and intellectual disability, the cardinal signs of this disease.

Wiedemann-Steiner syndrome as a major cause of syndromic intellectual disability: A study of 33 French cases

Wiedemann-Steiner syndrome (WSS) is a rare syndromic condition in which intellectual disability (ID) is associated with hypertrichosis cubiti, short stature, and characteristic facies. Following the identification of the causative gene (KMT2A) in 2012, only 31 cases of WSS have been described precisely in the literature. We report on 33 French individuals with a KMT2A mutation confirmed by targeted gene sequencing, high-throughput sequencing or exome sequencing. Patients' molecular and clinical features were recorded and compared with the literature data. On the molecular level, we found 29 novel mutations. We observed autosomal dominant transmission of WSS in 3 families and mosaicism in one family. Clinically, we observed a broad phenotypic spectrum with regard to ID (mild to severe), the facies (typical or not of WSS) and associated malformations (bone, cerebral, renal, cardiac and ophthalmological anomalies). Hypertrichosis cubiti that was supposed to be pathognomonic in the literature was found only in 61% of our cases. This is the largest series of WSS cases yet described to date. A majority of patients exhibited suggestive features, but others were less characteristic, only identified by molecular diagnosis. The prevalence of WSS was higher than expected in patients with ID, suggesting than KMT2A is a major gene in ID.

Molecular and cellular issues of KMT2A variants involved in Wiedemann-Steiner syndrome

Variants in KMT2A, encoding the histone methyltransferase KMT2A, are a growing cause of intellectual disability (ID). Up to now, the majority of KMT2A variants are non-sense and frameshift variants causing a typical form of Wiedemann-Steiner syndrome. We studied KMT2A gene in a cohort of 200 patients with unexplained syndromic and non-syndromic ID and identified four novel variants, one splice and three missense variants, possibly deleterious. We used primary cells from the patients and molecular approaches to determine the deleterious effects of those variants on KMT2A expression and function. For the putative splice variant c.11322-1G>A, we showed that it led to only one nucleotide deletion and loss of the C-terminal part of the protein. For two studied KMT2A missense variants, c.3460C>T (p.(Arg1154Trp)) and c.8558T>G (p.(Met2853Arg)), located at the cysteine-rich CXXC domain and the transactivation domain of the protein, respectively, we found altered KMT2A target genes expression in patient's fibroblasts compared to controls. Furthermore, we found a disturbed subcellular distribution of KMT2A for the c.3460C>T mutant. Taken together, our results demonstrated the deleterious impact of the splice variant and of the missense variants located at two different functional domains and suggested reduction of KMT2A function as the disease-causing mechanism.