Phenotypic spectrum and management issues in Kabuki syndrome

Clinical and molecular analysis of Guangxi patients with Kabuki syndrome and KMT2D mutations

Kabuki syndrome (KS) is a multiple congenital anomaly syndrome that is characterized by postnatal growth deficiency, hypotonia, short stature, mild-to-moderate intellectual disability, skeletal abnormalities, persistence of fetal fingertip pads, and distinct facial appearance. It is mainly caused by pathogenic/likely pathogenic variants in the KMT2D or KDM6A genes. Here, we described the clinical features of nine sporadic KS patients with considerable phenotypic heterogeneity. In addition to intellectual disability and short stature, our patients presented with a high prevalence of motor retardation and recurrent otitis media. We recommended that KS should be strongly considered in patients with motor delay, short stature, intellectual disability, language disorder and facial deformities. Nine KMT2D variants, four of which were novel, were identified by whole-exome sequencing. The variants included five nonsense variants, two frameshift variants, one missense variant, and one non-canonical splice site variant. In addition, we reviewed the mutation types of the pathogenic KMT2D variants in the ClinVar database. We also indicated that effective mRNA analysis, using biological materials from patients, is helpful in classifying the pathogenicity of atypical splice site variants. Pedigree segregation analysis may also provide valuable information for pathogenicity classification of novel missense variants. These findings extended the mutation spectrum of KMT2D and provided new insights into the understanding of genotype-phenotype correlations, which are helpful for accurate genetic counseling and treatment optimization.

Immune dysregulation in Kabuki syndrome: a case report of Evans syndrome and hypogammaglobulinemia

Kabuki syndrome (KS) is a rare multisystemic disease due to mutations in the KMT2D or KDM6A genes, which act as epigenetic modulators of different processes, including immune response. The syndrome is characterized by anomalies in multiple organ systems, and it is associated with autoimmune and inflammatory disorders, and an underlying immunological phenotype characterized by immunodeficiency and immune dysregulation. Up to 17% of KS patients present with immune thrombocytopenia characterized by a severe, chronic or relapsing course, and often associated to other hematological autoimmune diseases including autoimmune hemolytic anemia, eventually resulting in Evans syndrome (ES). A 23-year-old woman, clinically diagnosed with KS and presenting from the age of 3 years with ES was referred to the Rare Diseases Centre of our Pediatric Department for corticosteroid-induced hyperglycemia. Several ES relapses and recurrent respiratory infections in the previous years were reported. Severe hypogammaglobulinemia, splenomegaly and signs of chronic lung inflammation were diagnosed only at the time of our observation. Supportive treatment with amoxicillin-clavulanate prophylaxis and recombinant human hyaluronidase-facilitated subcutaneous immunoglobulin replacement were immediately started. In KS patients, the failure of B-cell development and the lack of autoreactive immune cells suppression can lead to immunodeficiency and autoimmunity that may be undiagnosed for a long time. Our patient's case is paradigmatic since she presented with preventable morbidity and severe lung disease years after disease onset. This case emphasizes the importance of suspecting immune dysregulation in KS. Pathogenesis and immunological complications of KS are discussed. Moreover, the need to perform immunologic evaluations is highlighted both at the time of KS diagnosis and during disease follow-up, in order to allow proper treatment while intercepting avoidable morbidity in these patients.

From Genotype to Phenotype-A Review of Kabuki Syndrome

Kabuki syndrome (KS) is a rare neuro-developmental disorder caused by variants in genes of histone modification, including KMT2D and KDM6A. This review assesses our current understanding of KS, which was originally named Niikawa-Kuroki syndrome, and aims to guide surveillance and medical care of affected individuals as well as identify gaps in knowledge and unmet patient needs. Ovid MEDLINE and EMBASE databases were searched from 1981 to 2021 to identify reports related to genotype and systems-based phenotype characterization of KS. A total of 2418 articles were retrieved, and 152 were included in this review, representing a total of 1369 individuals with KS. Genotype, phenotype, and the developmental and behavioral profile of KS are reviewed. There is a continuous clinical phenotype spectrum associated with KS with notable variability between affected individuals and an emerging genotype-phenotype correlation. The observed clinical variability may be attributable to differences in genotypes and/or unknown genetic and epigenetic factors. Clinical management is symptom oriented, fragmented, and lacks established clinical care standards. Additional research should focus on enhancing understanding of the burden of illness, the impact on quality of life, the adult phenotype, life expectancy and development of standard-of-care guidelines.

Bate palmas mutant mice as a model of Kabuki syndrome: Higher susceptibility to infections and vocalization impairments?

The recessive mutant mouse bate palmas (bapa) arose from N-ethyl-N-nitrosourea mutagenesis. Previous studies of our group revealed some behavioral impairments and a mutation in the lysine (K)-specific methyltransferase 2D (Kmt2d) gene. Because mutations in the KMT2D gene in humans are mainly responsible for Kabuki syndrome, this study was proposed to validate bapa mice as a model of Kabuki syndrome. Besides other symptoms, Kabuki syndrome is characterized by increased susceptibility to infections and speech impairments, usually diagnosed in the early childhood. Thus, juvenile male and female bapa mice were studied in different developmental stages (prepubertal period and puberty). To induce sickness behavior and to study infection susceptibility responses, lipopolysaccharide (LPS) was used. To study oral communication, ultrasonic vocalizations were evaluated. Behavioral (open-field test) and central (astrocytic glial fibrillary acidic protein [GFAP] and tyrosine hydroxylase [TH]) evaluations were also performed. Control and bapa female mice emitted 31-kHz ultrasounds on prepubertal period when exploring a novel environment, a frequency not yet described for mice, being defined as 31-kHz exploratory vocalizations. Males, LPS, and puberty inhibited these vocalizations. Bapa mice presented increased motor/exploratory behaviors on prepubertal period due to increased striatal TH expression, revealing striatal dopaminergic system hyperactivity. Combining open-field behavior and GFAP expression, bapa mice did not develop LPS tolerance, that is, they remained expressing signs of sickness behavior after LPS challenge, being more susceptible to infectious/inflammatory processes. It was concluded that bapa mice is a robust experimental model of Kabuki syndrome.

Singleton exome sequencing of 90 fetuses with ultrasound anomalies revealing novel disease-causing variants and genotype-phenotype correlations

Exome sequencing has been increasingly implemented in prenatal genetic testing for fetuses with morphological abnormalities but normal rapid aneuploidy detection and microarray analysis. We present a retrospective study of 90 fetuses with different abnormal ultrasound findings, in which we employed the singleton exome sequencing (sES; 75 fetuses) or to a lesser extent (15 fetuses) a multigene panel analysis of 6713 genes as a primary tool for the detection of monogenic diseases. The detection rate of pathogenic or likely pathogenic variants in this study was 34.4%. The highest diagnostic rate of 56% was in fetuses with multiple anomalies, followed by cases with skeletal or renal abnormalities (diagnostic rate of 50%, respectively). We report 20 novel disease-causing variants in different known disease-associated genes and new genotype-phenotype associations for the genes KMT2D, MN1, CDK10, and EXOC3L2. Based on our data, we postulate that sES of fetal index cases with a concurrent sampling of parental probes for targeted testing of the origin of detected fetal variants could be a suitable tool to obtain reliable and rapid prenatal results, particularly in situations where a trio analysis is not possible.

Reprogramming of the epigenome in neurodevelopmental disorders

The etiology of neurodevelopmental disorders (NDDs) remains a challenge for researchers. Human brain development is tightly regulated and sensitive to cellular alterations caused by endogenous or exogenous factors. Intriguingly, the surge of clinical sequencing studies has revealed that many of these disorders are monogenic and monoallelic. Notably, chromatin regulation has emerged as highly dysregulated in NDDs, with many syndromes demonstrating phenotypic overlap, such as intellectual disabilities, with one another. Here we discuss epigenetic writers, erasers, readers, remodelers, and even histones mutated in NDD patients, predicted to affect gene regulation. Moreover, this review focuses on disorders associated with mutations in enzymes involved in histone acetylation and methylation, and it highlights syndromes involving chromatin remodeling complexes. Finally, we explore recently discovered histone germline mutations and their pathogenic outcome on neurological function. Epigenetic regulators are mutated at every level of chromatin organization. Throughout this review, we discuss mechanistic investigations, as well as various animal and iPSC models of these disorders and their usefulness in determining pathomechanism and potential therapeutics. Understanding the mechanism of these mutations will illuminate common pathways between disorders. Ultimately, classifying these disorders based on their effects on the epigenome will not only aid in prognosis in patients but will aid in understanding the role of epigenetic machinery throughout neurodevelopment.

Personalized Genetic Diagnosis of Congenital Heart Defects in Newborns

Congenital heart disease is a group of pathologies characterized by structural malformations of the heart or great vessels. These alterations occur during the embryonic period and are the most frequently observed severe congenital malformations, the main cause of neonatal mortality due to malformation, and the second most frequent congenital malformations overall after malformations of the central nervous system. The severity of different types of congenital heart disease varies depending on the combination of associated anatomical defects. The causes of these malformations are usually considered multifactorial, but genetic variants play a key role. Currently, use of high-throughput genetic technologies allows identification of pathogenic aneuploidies, deletions/duplications of large segments, as well as rare single nucleotide variants. The high incidence of congenital heart disease as well as the associated complications makes it necessary to establish a diagnosis as early as possible to adopt the most appropriate measures in a personalized approach. In this review, we provide an exhaustive update of the genetic bases of the most frequent congenital heart diseases as well as other syndromes associated with congenital heart defects, and how genetic data can be translated to clinical practice in a personalized approach.

Kabuki Syndrome-Clinical Review with Molecular Aspects

Kabuki syndrome (KS) is a rare developmental disorder principally comprised of developmental delay, hypotonia and a clearly defined dysmorphism: elongation of the structures surrounding the eyes, a shortened and depressed nose, thinning of the upper lip and thickening of the lower lip, large and prominent ears, hypertrichosis and scoliosis. Other characteristics include poor physical growth, cardiac, gastrointestinal and renal anomalies as well as variable behavioral issues, including autistic features. De novo or inherited pathogenic/likely pathogenic variants in the KMT2D gene are the most common cause of KS and account for up to 75% of patients. Variants in KDM6A cause up to 5% of cases (X-linked dominant inheritance), while the etiology of about 20% of cases remains unknown. Current KS diagnostic criteria include hypotonia during infancy, developmental delay and/or intellectual disability, typical dysmorphism and confirmed pathogenic/likely pathogenic variant in KMT2D or KDM6A. Care for KS patients includes the control of physical and psychomotor development during childhood, rehabilitation and multi-specialist care. This paper reviews the current clinical knowledge, provides molecular and scientific links and sheds light on the treatment of Kabuki syndrome individuals.

Congenital Hypothyroidism: A 2020-2021 Consensus Guidelines Update-An ENDO-European Reference Network Initiative Endorsed by the European Society for Pediatric Endocrinology and the European Society for Endocrinology

Background: An ENDO-European Reference Network (ERN) initiative was launched that was endorsed by the European Society for Pediatric Endocrinology and the European Society for Endocrinology with 22 participants from the ENDO-ERN and the two societies. The aim was to update the practice guidelines for the diagnosis and management of congenital hypothyroidism (CH). A systematic literature search was conducted to identify key articles on neonatal screening, diagnosis, and management of primary and central CH. The evidence-based guidelines were graded with the Grading of Recommendations, Assessment, Development and Evaluation system, describing both the strength of recommendations and the quality of evidence. In the absence of sufficient evidence, conclusions were based on expert opinion. Summary: The recommendations include the various neonatal screening approaches for CH as well as the etiology (also genetics), diagnostics, treatment, and prognosis of both primary and central CH. When CH is diagnosed, the expert panel recommends the immediate start of correctly dosed levothyroxine treatment and frequent follow-up including laboratory testing to keep thyroid hormone levels in their target ranges, timely assessment of the need to continue treatment, attention for neurodevelopment and neurosensory functions, and, if necessary, consulting other health professionals, and education of the child and family about CH. Harmonization of diagnostics, treatment, and follow-up will optimize patient outcomes. Lastly, all individuals with CH are entitled to a well-planned transition of care from pediatrics to adult medicine. Conclusions: This consensus guidelines update should be used to further optimize detection, diagnosis, treatment, and follow-up of children with all forms of CH in the light of the most recent evidence. It should be helpful in convincing health authorities of the benefits of neonatal screening for CH. Further epidemiological and experimental studies are needed to understand the increased incidence of this condition.

Facial Dysmorphisms, Macrodontia, Focal Epilepsy, and Thinning of the Corpus Callosum: A Rare Mild Form of Kabuki Syndrome

Kabuki syndrome (KS) is a rare genetic condition with multiple congenital abnormalities and developmental delay. The cardinal manifestations of KS include characteristic facial features, intellectual disability, skeletal defects, dermatoglyphic abnormalities, and postnatal growth deficiencies. Cardiac and urological malformations are commonly present in patient with KS, as well as language deficits and immunological abnormalities. Here, we reported a case of a child with an atypical form of KS, associated with macrodontia, corpus callosum dysmorphism, focal epilepsy responsive to antiepileptic treatment, and a novel KMT2D gene missense variant, c.2413C > T, never reported to date.

Using Xenopus to analyze neurocristopathies like Kabuki syndrome

Neurocristopathies are human congenital syndromes that arise from defects in neural crest (NC) development and are typically associated with malformations of the craniofacial skeleton. Genetic analyses have been very successful in identifying pathogenic mutations, however, model organisms are required to characterize how these mutations affect embryonic development thereby leading to complex clinical conditions. The African clawed frog Xenopus laevis provides a broad range of in vivo and in vitro tools allowing for a detailed characterization of NC development. Due to the conserved nature of craniofacial morphogenesis in vertebrates, Xenopus is an efficient and versatile system to dissect the morphological and cellular phenotypes as well as the signaling events leading to NC defects. Here, we review a set of techniques and resources how Xenopus can be used as a disease model to investigate the pathogenesis of Kabuki syndrome and neurocristopathies in a wider sense.

Comparative meta-analysis of Kabuki syndrome with and without hyperinsulinaemic hypoglycaemia

BACKGROUND AND OBJECTIVE

Kabuki syndrome (KS), caused by pathogenic variants in KMT2D or KDM6A, is associated with hyperinsulinaemic hypoglycaemia (HH) in 0.3%-4% of patients. We characterized the clinical, biochemical and molecular data of children with KS and HH compared to children with KS without HH in a multicentre meta-analysis.

METHODS

Data of seven new and 17 already published children with KS and HH were compared to 373 recently published KS patients without HH regarding molecular and clinical characteristics.

RESULTS

Seven new patients were identified with seven different pathogenic variants in KDM6A (n = 4) or KMT2D (n = 3). All presented with HH on the first day of life and were responsive to diazoxide. KS was diagnosed between 9 months and 14 years of age. In the meta-analysis, 24 KS patients with HH had a significantly higher frequency of variants in KDM6A compared to 373 KS patients without HH (50% vs 11.5%, P < .001), and KDM6A-KS was more likely to be associated with HH than KMT2D-KS (21.8% vs. 3.5%, P < .001). Sex distribution and other phenotypic features did not differ between KS with and without HH.

CONCLUSION

The higher incidence of HH in KDM6A-KS compared to KMT2D-KS indicates that KDM6A loss of function variants predispose more specifically to beta cell dysfunction compared to KMT2D variants. As difficulties to assign syndromic characteristics to KS in early infancy often lead to delayed diagnosis, genetic testing for KS should be considered in children with HH, especially in the presence of other extrapancreatic/syndromic features.

De novo missense variants in the RAP1B gene identified in two patients with syndromic thrombocytopenia

We present two independent cases of syndromic thrombocytopenia with multiple malformations, microcephaly, learning difficulties, dysmorphism and other features. Exome sequencing identified two novel de novo heterozygous variants in these patients, c.35G>T p.(Gly12Val) and c.178G>C p.(Gly60Arg), in the RAP1B gene (NM_001010942.2). These variants have not been described previously as germline variants, however functional studies in literature strongly suggest a clinical implication of these two activating hot spot positions. We hypothesize that pathogenic missense variants in the RAP1B gene cause congenital syndromic thrombocytopenia with a spectrum of associated malformations and dysmorphism, possibly through a gain of function mechanism.

EpigenCentral: Portal for DNA methylation data analysis and classification in rare diseases

Epigenetic processes play a key role in regulating gene expression. Genetic variants that disrupt chromatin-modifying proteins are associated with a broad range of diseases, some of which have specific epigenetic patterns, such as aberrant DNA methylation (DNAm), which may be used as disease biomarkers. While much of the epigenetic research has focused on cancer, there is a paucity of resources devoted to neurodevelopmental disorders (NDDs), which include autism spectrum disorder and many rare, clinically overlapping syndromes. To address this challenge, we created EpigenCentral, a free web resource for biomedical researchers, molecular diagnostic laboratories, and clinical practitioners to perform the interactive classification and analysis of DNAm data related to NDDs. It allows users to search for known disease-associated patterns in their DNAm data, classify genetic variants as pathogenic or benign to assist in molecular diagnostics, or analyze patterns of differential methylation in their data through a simple web form. EpigenCentral is freely available at http://epigen.ccm.sickkids.ca/.

Joint hypermobility in children: a neglected sign needing more attention

Joint hypermobility refers to the ability that a joint has to move beyond its normal range of motion. It is common in the general population, particularly in children. While many individuals manifesting joint hypermobility are healthy, this feature can accompany a wide range of symptoms and systemic disorders, whose management can be influenced by their prompt recognition. Given the increasing attention that joint hypermobility is attracting in various fields of medicine, many practitioners are asked to approach more carefully joint hypermobility, in order to avoid over- and under-diagnosis of related disorders. Among the most common conditions featuring joint hypermobility there are hypermobility spectrum disorders and hereditary connective tissue disorders, in particular, the Ehlers-Danlos syndromes. In children, joint hypermobility also accompany a variety of disorders affecting neurodevelopment. The nature of such an association is protean, as joint hypermobility may occur in selected congenital neuromuscular disorders, monogenic multiple malformation/intellectual disability syndromes, and well-known and emerging genomic syndromes. In addition, joint hypermobility seems strongly associated with developmental coordination disorders. This review offers an overview on definitions, assessment procedures, patterns of associated manifestations and disorders related to joint hypermobility, as well as treatment principles of associated musculoskeletal pain for practitioners that are not familial with this issue but encounter people featuring this physical attribute in their daily activity.

Salzmann nodular degeneration features in a case of Kabuki make-up syndrome

Kabuki syndrome (KS) is a multiple congenital anomaly syndrome with diversified ophthalmological manifestations. We report a case of a boy with bilateral features of Salzmann nodular degeneration (SND) associated with KS. An 18-year-old Caucasian man with KS presented for a second opinion regarding incapacitating photophobia in his right eye, refractory to medical therapy. Biomicroscopy revealed bilateral subepithelial nodules in the midperiphery of the cornea, less extensive in the left eye, consistent with SND. Symptomatic improvement was achieved after superficial keratectomy, manually performed with a blade and adjuvant application of mitomycin C. We report a rare case of a KS patient with SND. Since KS manifestations may vary widely, it is important to perform an early ophthalmological examination for prompt detection and treatment of ocular abnormalities and thus improve life quality in these patients.

Pulmonary Manifestations of Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is associated with significant chronic lung disease. The purpose of this paper was to describe the clinical, radiologic, and pathologic findings of CVID-associated lung diseases. These include airways' disease, interstitial lung disease, lymphoma, and mucosa-associated lymphoid tissue lymphoma. In addition, a genetic syndrome termed Kabuki syndrome results in CVID-like immune abnormalities. These patients may also present with CVID-associated lung disease. Awareness and precise identification of CVID-associated lung disease may allow for better assessment of prognosis and direction of therapy.

Hypermobility in individuals with Kabuki syndrome: The effect of growth hormone treatment

Kabuki syndrome (KS) is a multiple congenital malformation syndrome which has been described across all ethnic groups. Most KS patients possess two genetic subtypes: KMT2D-associated, autosomal-dominant KS type 1 (KS1; OMIM 147920); and KDM6A-associated, X-linked-dominant KS type 2. Generalized joint hypermobility is one feature of KS, but its exact incidence and pattern is not well described in the literature. As part of our prospective study on the metabolic and growth effect of GH treatment, we assessed children from our Dutch Kabuki cohort who were eligible for growth hormone therapy. We assessed severity and pattern of joint hypermobility, both before and after 24 months of growth hormone replacement therapy. The prevalence of hypermobility was 31% in boys and 14% in girls using the Beighton score and 69% in boys and 57% in girls using the Bulbena score. This varies from the general population where girls are more affected. After 2 years of growth hormone treatment, there was a statistically significant decrease in the presence of joint hypermobility to 6% using the Bulbena score and none with respect to the Beighton score. We hypothesized that this result suggests a direct effect of growth hormone on connective tissue in patients with KS.

Pharmacological resources, diagnostic approach and coordination of care in joint hypermobility-related disorders

INTRODUCTION

Joint hypermobility (JH) is the hallmark of many hereditary soft connective tissue disorders, including Ehlers-Danlos syndromes and related disorders, disorders of the TGFβ-pathway, lateral meningocele syndrome, arterial tortuosity syndrome, and cutis laxa syndromes. Contemporary practice separates individuals with isolated, non-syndromic JH from patients with Mendelian syndromes and those with hypermobility spectrum disorders. The latter is a new nosologic entity grouping together individuals with JH and related musculoskeletal manifestations, but lacking inclusion criteria for well-defined and/or single-gene disorders. Area covered: Nomenclature of JH and JH-related disorders are summarized on a practically oriented perspective. Critical areas of clinical management comprise pain; cardiovascular and respiratory issues; fatigue and dysautonomia; bone fragility; and capillary, skin and soft tissue fragility. Medical management stands on low-evidence data. Ongoing preclinical and clinical studies are aimed to reach a more personalized pharmacological approach to the management of the cardiovascular risk, musculoskeletal pain, and reduced bone mass. Expert commentary: Correct classification of patients with JH-related disorders needs a systematic approach, in which a wide array of molecular tests should be intermingled with strong clinical competences in highly specialized settings. A multispecialty, hierarchical approach should be encouraged for optimal coordination of care in systemic phenotypes.

A de novo KMT2D mutation in a girl with Kabuki syndrome associated with endocrine symptoms: a case report

BACKGROUND

Kabuki syndrome is characterized by distinctive facial features and varying degrees of growth retardation. It leads to malformations in skeletal, urogenital and cardiac structures; moreover, endocrine conditions such as premature thelarche, precocious puberty, growth hormone deficiency, diabetes insipidus, thyroid dysfunction and obesity have been reported. Kabuki syndrome is caused by a heterozygous mutation in the KMT2D or KDM6A genes.

CASE PRESENTATION

An 11-year-old girl with the typical facial features of Kabuki syndrome visited our hospital due to her short stature. She was found to have the de novo heterozygous mutation of c.8200C > T, p(Arg2734*) in exon 32 of the KMT2D gene and was diagnosed with Kabuki syndrome. The patient also exhibited endocrine abnormalities such as a constitutional delay of puberty, transiently congenial hypothyroidism, obesity and growth hormone deficiency.

CONCLUSIONS

This is a case of a mutation in the KMT2D gene in a girl with Kabuki syndrome who presented with endocrine symptoms (constitutional delay of puberty, hypothyroidism, obesity and growth hormone deficiency).

Cleft Palate in Kabuki Syndrome: A Report of Six Cases

Kabuki syndrome is a syndrome of rare congenital anomalies that was named after its characteristic appearance, a face resembling that of an actor in a Kabuki play. Although cleft palate is a feature that is sometimes observed in patients with Kabuki syndrome, there are few clinical reports of cleft palate associated with Kabuki syndrome. This report presents six cases of Kabuki syndrome with cleft palate and reviews their clinical features. Our results suggest that (1) patients with cleft palate in Kabuki syndrome tend to fail in acquiring normal velopharyngeal function and (2) submucous cleft palate might be more common in patients with Kabuki syndrome than previously was reported.

Update on 13 Syndromes Affecting Craniofacial and Dental Structures

Care of individuals with syndromes affecting craniofacial and dental structures are mostly treated by an interdisciplinary team from early childhood on. In addition to medical and dental specialists that have a vivid interest in these syndromes and for whom these syndromes are of evident interest, experts of scientific background-like molecular and developmental geneticists, but also computational biologists and bioinformaticians-, become more frequently involved in the refined diagnostic and etiological processes of these patients. Early diagnosis is often crucial for the effective treatment of functional and developmental aspects. However, not all syndromes can be clinically identified early, especially in cases of absence of known family history. Moreover, the treatment of these patients is often complicated because of insufficient medical knowledge, and because of the dental and craniofacial developmental variations. The role of the team is crucial for the prevention, proper function, and craniofacial development which is often combined with orthognathic surgery. Although the existing literature does not provide considerable insight into this topic, this descriptive review aims to provide tools for the interdisciplinary team by giving an update on the genetics and general features, and the oral and craniofacial manifestations for early diagnosis. Clinical phenotyping together with genetic data and pathway information will ultimately pave the way for preventive strategies and therapeutic options in the future. This will improve the prognosis for better functional and aesthetic outcome for these patients and lead to a better quality of life, not only for the patients themselves but also for their families. The aim of this review is to promote interdisciplinary interaction and mutual understanding among all specialists involved in the diagnosis and therapeutic guidance of patients with these syndromal conditions in order to provide optimal personalized care in an integrated approach.

Characteristics of epilepsy in patients with Kabuki syndrome with KMT2D mutations

BACKGROUND

The characteristics of epilepsy in patients with Kabuki syndrome with KMT2D mutations (KABUK1) have not yet been well documented. This is the first review to explore this.

MATERIALS & METHODS

We enrolled 14 patients with KABUK1, whose median age was 13.6years (range=4.1-21.3years). Their medical records from October 1981 to May 2016 were retrospectively analyzed.

RESULTS

Epilepsy was present in 5 (36%) patients. Four of these patients presented with nonsense mutations and one with missense mutations. None presented with brain abnormalities. Four patients presented with annual or monthly focal seizures, of which three evolved to bilateral convulsive seizures. Median onset age of focal epilepsy was 11.8years (range=9.5-12.8years). One presented with monthly myoclonic seizures from age 11.2, whose mother with no other KABUK1 features, had focal epilepsy. The cumulative incidence of epilepsy related to KABUK1 up until age 13 was 45%. Interictal electroencephalogram revealed focal paroxysmal epileptiform discharges (in frontal, central, and parietal regions) in three patients, diffuse high-voltage spike-and-waves in one patient, and normal sleep record in one patient. Myoclonic seizures were rapidly controlled by levetiracetam. In contrast, focal seizures were not controlled in the early period of antiepileptic therapy.

CONCLUSION

This long-term follow-up of patients with KABUK1 revealed a higher prevalence of epilepsy than previously reported. The age of epilepsy onset and rate of focal seizures evolving to bilateral convulsive seizures in KABUK1 were also higher than previously reported in patients with clinically diagnosed Kabuki syndrome. Although seizure outcome is reported to be favorable in Kabuki syndrome, focal seizures in patients with KABUK1 were not immediately responsive to medication.

On the significance of craniosynostosis in a case of Kabuki syndrome with a concomitant KMT2D mutation and 3.2 Mbp de novo 10q22.3q23.1 deletion

Craniosynostosis has rarely been described in patients with Kabuki syndrome. We report here a boy with facial asymmetry due to combined premature synostosis of the right coronal and sagittal sutures as well as several symptoms reminiscent of Kabuki syndrome (KS). Our case supports previous observations and suggests that craniosynostosis is a part of the KS phenotype. The uniqueness of our case is the sporadic co-occurrence of two genetic disorders, that is, a de novo frameshift variant in the KMT2D gene and a de novo 3.2 Mbp 10q22.3q23.1 deletion. Our findings emphasize the importance of the initial clinical assessment of children with craniosynostosis and that genomic and monogenic disorders, such as Kabuki syndrome, should be considered among the differential diagnoses of syndromic forms of craniosynostosis.

Disorders of thyroid morphogenesis

Developmental anomalies of the thyroid gland, defined as thyroid dysgenesis, underlie the majority of cases of congenital hypothyroidism. Thyroid dysgenesis is predominantly a sporadic disorder although a reported familial enrichment, variation of incidence by ethnicity and the monogenic defects associated mainly with athyreosis or orthotopic thyroid hypoplasia, suggest a genetic contribution. Of note, the most common developmental anomaly, thyroid ectopy, remains unexplained. Ectopy may result from multiple genetic or epigenetic variants in the germline and/or at the somatic level. This review provides a brief overview of the monogenic defects in candidate genes that have been identified so far and of the syndromes which are known to be associated with thyroid dysgenesis.

A framework for the classification of joint hypermobility and related conditions

In the last decade, growing attention has been placed on joint hypermobility and related disorders. The new nosology for Ehlers-Danlos syndrome (EDS), the best-known and probably the most common of the disorders featuring joint hypermobility, identifies more than 20 different types of EDS, and highlights the need for a single set of criteria to substitute the previous ones for the overlapping EDS hypermobility type and joint hypermobility syndrome. Joint hypermobility is a feature commonly encountered in many other disorders, both genetic and acquired, and this finding is attracting the attention of an increasing number of medical and non-medical disciplines. In this paper, the terminology of joint hypermobility and related disorders is summarized. Different types of joint hypermobility, its secondary musculoskeletal manifestations and a simplified categorization of genetic syndromes featuring joint hypermobility are presented. The concept of a spectrum of pathogenetically related manifestations of joint hypermobility intersecting the categories of pleiotropic syndromes with joint hypermobility is introduced. A group of hypermobility spectrum disorders is proposed as diagnostic labels for patients with symptomatic joint hypermobility but not corresponding to any other syndromes with joint hypermobility. © 2017 Wiley Periodicals, Inc.

Epigenetic control of the immune system: a lesson from Kabuki syndrome

Kabuki syndrome (KS) is a rare multi-systemic disorder characterized by a distinct face, postnatal growth deficiency, mild-to-moderate intellectual disability, skeletal and visceral (mainly cardiovascular, renal, and skeletal) malformations, dermatoglyphic abnormalities. Its cause is related to mutations of two genes: KMT2D (histone-lysine N-methyltransferase 2D) and KDM6A (lysine-specific demethylase 6A), both functioning as epigenetic modulators through histone modifications in the course of embryogenesis and in several biological processes. Epigenetic regulation is defined as the complex of hereditable modifications to DNA and histone proteins that modulates gene expression in the absence of DNA nucleotide sequence changes. Different human disorders are caused by mutations of genes involved in the epigenetic regulation, and not surprisingly, all these share developmental defects, disturbed growth (in excess or defect), multiple congenital organ malformations, and also hematological and immunological defects. In particular, most KS patients show increased susceptibility to infections and have reduced serum immunoglobulin levels, while some suffer also from autoimmune manifestations, such as idiopathic thrombocytopenic purpura, hemolytic anemia, autoimmune thyroiditis, and vitiligo. Herein we review the immunological aspects of KS and propose a novel model to account for the immune dysfunction observed in this condition.

Recurrent giant cell fibroblastoma: Malignancy predisposition in Kabuki syndrome revisited

Kabuki syndrome is a genetic condition characterized by distinctive facial phenotype, mental retardation, and internal organ malformations. Mutations of the epigenetic genes KMT2D and KDM6A cause dysregulation of certain developmental genes and account for the multiple congenital anomalies of the syndrome. Eight cases of malignancies have been reported in young patients with Kabuki syndrome although a causative association to the syndrome has not been established. We report a case of a 12-year-old girl with Kabuki syndrome who developed a tumor on the right side of her neck. A relapsing tumor 19 months after initial excision, proved to be giant cell fibroblastoma. Τhis is the first report of giant cell fibroblastoma -a rare tumor of childhood- in a patient with Kabuki syndrome.

Defects of B-cell terminal differentiation in patients with type-1 Kabuki syndrome

BACKGROUND

Kabuki syndrome (KS) is a complex multisystem developmental disorder associated with mutation of genes encoding histone-modifying proteins. In addition to craniofacial, intellectual, and cardiac defects, KS is also characterized by humoral immune deficiency and autoimmune disease, yet no detailed molecular characterization of the KS-associated immune phenotype has been reported.

OBJECTIVE

We sought to characterize the humoral immune defects found in patients with KS with lysine methyltransferase 2D (KMT2D) mutations.

METHODS

We comprehensively characterized B-cell function in a cohort (n = 13) of patients with KS (age, 4 months to 27 years).

RESULTS

Three quarters (77%) of the cohort had a detectable heterozygous KMT2D mutation (50% nonsense, 20% splice site, and 30% missense mutations), and 70% of the reported mutations are novel. Among the patients with KMT2D mutations (KMT2D(Mut/+)), hypogammaglobulinemia was detected in all but 1 patient, with IgA deficiency affecting 90% of patients and a deficiency in at least 1 other isoform seen in 40% of patients. Numbers of total memory (CD27(+)) and class-switched memory B cells (IgM(-)) were significantly reduced in patients with KMT2D(Mut/+) mutations compared with numbers in control subjects (P < .001). Patients with KMT2D(Mut/+) mutations also had significantly reduced rates of somatic hypermutation in IgG (P = .003) but not IgA or IgM heavy chain sequences. Impaired terminal differentiation was noted in primary B cells from patients with KMT2D(Mut/+) mutations. Autoimmune pathology was observed in patients with missense mutations affecting the SET domain and its adjacent domains.

CONCLUSIONS

In patients with KS, autosomal dominant KMT2D mutations are associated with dysregulation of terminal B-cell differentiation, leading to humoral immune deficiency and, in some cases, autoimmunity. All patients with KS should undergo serial clinical immune evaluations.

Kabuki Syndrome and Anorectal Malformations: Implications for Diagnosis and Treatment

Kabuki syndrome (KS) is a rare genetic condition characterized by a distinctive facies, intellectual disability, growth delay, and a variety of skeletal, visceral, and other anomalies, including anorectal malformations (ARMs). We present two cases of female patients with KS, diagnosed and successfully managed at our institution, one with a perineal fistula and one with a rectovestibular fistula. Our report, along with a literature review, shows that the syndrome is usually associated with "low" anomalies, with a potential for a good prognosis. Management of the anorectal anomaly in patients with KS is not essentially different from that in other nonsyndromic patients, taking into account the frequent association of the syndrome with serious congenital heart disease, which might affect the decision-making and timing of the stages of anorectal reconstruction. The frequent occurrence of learning and feeding difficulties makes establishment of toilet training and bowel management rather more challenging, requiring the expertise of a multidisciplinary team. The finding of ARMs in female patients with other characteristics of KS, although inconstant, could support the clinical suspicion for the syndrome until genetic confirmation is available, and should alert the physician for the potential of severe cardiac defects.

Kabuki syndrome genes KMT2D and KDM6A: functional analyses demonstrate critical roles in craniofacial, heart and brain development

Kabuki syndrome (KS) is a rare multiple congenital anomaly syndrome characterized by distinctive facial features, global developmental delay, intellectual disability and cardiovascular and musculoskeletal abnormalities. While mutations in KMT2D have been identified in a majority of KS patients, a few patients have mutations in KDM6A. We analyzed 40 individuals clinically diagnosed with KS for mutations in KMT2D and KDM6A. Mutations were detected in KMT2D in 12 and KDM6A in 4 cases, respectively. Observed mutations included single-nucleotide variations and indels leading to frame shifts, nonsense, missense or splice-site alterations. In two cases, we discovered overlapping chromosome X microdeletions containing KDM6A. To further elucidate the functional roles of KMT2D and KDM6A, we knocked down the expression of their orthologs in zebrafish. Following knockdown of kmt2d and the two zebrafish paralogs kdm6a and kdm6al, we analyzed morphants for developmental abnormalities in tissues that are affected in individuals with KS, including craniofacial structures, heart and brain. The kmt2d morphants exhibited severe abnormalities in all tissues examined. Although the kdm6a and kdm6al morphants had similar brain abnormalities, kdm6a morphants exhibited craniofacial phenotypes, whereas kdm6al morphants had prominent defects in heart development. Our results provide further support for the similar roles of KMT2D and KDM6A in the etiology of KS by using a vertebrate model organism to provide direct evidence of their roles in the development of organs and tissues affected in KS patients.

Kabuki syndrome: clinical and molecular diagnosis in the first year of life

OBJECTIVE

To review the clinical and molecular genetic characteristics of 16 patients presenting a suspected diagnosis of Kabuki syndrome (KS) in the first year of life, to evaluate the clinical handles leading to a prompt diagnosis of KS in newborns. Clinical diagnosis of KS can be challenging during the first year of life, as many diagnostic features become evident only in subsequent years.

METHODS

All patients were clinically investigated by trained clinical geneticists. A literature review was performed using the Pubmed online database and diagnostic criteria suggested by DYSCERNE-Kabuki Syndrome Guidelines (2010) were used (a European Network of Centres of Expertise for Dysmorphology, funded by the European Commission Executive Agency for Health and Consumers (DG Sanco), Project 2006122). Molecular analysis of the known causative genes of KS, KMT2D/MLL2 and KDM6A, was performed through MiSeq-targeted sequencing platform. All mutations identified were validated by Sanger sequencing protocols.

RESULTS

Mutations in KMT2D gene were identified in 10/16 (62%) of the patients, whereas none of the patients had KDM6A mutations. Facial dysmorphisms (94%), feeding difficulties (100%) and hypotonia (100%) suggested the clinical diagnosis of KS. No significative differences in terms of facial features were noticed between mutation positive and negative patients of the cohort. Brachydactyly, joint laxity and nail dysplasia were present in about 80% of the patients. Other congenital anomalies were most commonly present in the mutated group of patients, including left-sided cardiac abnormalities, skeletal, renal and anorectal malformations and hypertricosis.

CONCLUSIONS

We present an overview of patients with KS diagnosed during the first year of life. Early diagnosis is serviceable in terms of clinical management and for targeted genetic counselling.

Autoimmune haematological disorders in two Italian children with Kabuki syndrome

Kabuki syndrome (also called Niikawa-Kuroki syndrome) is a rare genetic disease described for the first time in Japan, characterised by anomalies in multiple organ systems and often associated with autoimmune disorders and impaired immune response. We herein report the clinical history, the therapeutic approach and the outcome of two children with Kabuki syndrome who developed autoimmune haematological disorders (haemolytic anaemia and immune thrombocytopenia). Factors regarding differential diagnosis and interventions in better management of this syndrome and its complications are discussed. This is the first report of Italian children with autoimmune haematological disorders complicating Kabuki syndrome.

Lower lip pits: van der woude or kabuki syndrome?

Kabuki syndrome (KS) is a multiple congenital anomaly/mental retardation syndrome with characteristic facial features. Despite more than 350 documented cases and recent correlation of MLL2 mutations as a genetic cause, its full clinical spectrum is still being defined. This report describes two patients who were initially diagnosed with Van der Woude syndrome (VWS) based on the presence of lower lip pits. However, this finding can occur with KS, albeit infrequently. For patients with lower lip pits, a thorough evaluation should be made to distinguish between VWS and KS, as there are differences in long-term prognosis.

Clinical and molecular spectrum of renal malformations in Kabuki syndrome

OBJECTIVE

To determine the frequency and types of renal malformations, and to evaluate renal function in a cohort of patients with Kabuki syndrome (KS).

STUDY DESIGN

Renal ultrasound scans and plasma creatinine measurements were collected from a French cohort of 94 patients with genotyped KS. Renal function was evaluated based on the estimated glomerular filtration rate. A genotype-phenotype study was conducted for renal and urinary tract malformations.

RESULTS

Renal malformations were present in 22% of cases, and urinary tract anomalies were present in 15%. Renal malformations were observed in 28% of the MLL2 mutation-positive group and in 0% of the MLL2 mutation-negative group (P = .015). No correlation was found between the presence or absence of renal or urinary tract malformations and the location or type of MLL2 mutation. Renal function was normal except for 1 patient with a MLL2 mutation diagnosed in the first days of life and severe renal disease due to unilateral renal agenesia and controlateral severe hypoplasia that progressed to the terminal stage at age 2 years.

CONCLUSION

Our study emphasizes the need for ultrasound and renal function screening in children diagnosed with KS.

Hypothalamic pituitary complications in Kabuki syndrome

Kabuki syndrome is characterized by distinctive facial features, multiple anomalies and mental retardation. In this syndrome, structural CNS abnormalities are commonly observed, but congenital abnormalities in the pituitary gland or hypothalamus have rarely been reported. We searched the published medical literature on the complications in hypothalamic pituitary axis in this syndrome. As a result, only nine patients with Kabuki syndrome had been reported to have complications in hypothalamic pituitary axis in previous papers. Among the nine reported patients and one presented case in this report, GH deficiency was the most frequent complication and found in six patients. Precocious puberty and central diabetes insipidus (DI) was identified in two cases, respectively, and ACTH deficiency was found in one. One case had combination of GH deficiency and central DI. Three of the 10 patients demonstrated abnormal pituitary findings in MRI study. Two of the six patients with GH deficiency were accompanied with premature thelarche. This review highlights that patients with Kabuki syndrome could present various clinical manifestations due to abnormalities in hypothalamic pituitary axis.

Recurrent dislocation of the patella in kabuki make-up syndrome

Two patients with Kabuki make-up syndrome with bilateral recurrent dislocation of the patella are presented. They had generalized ligamentous laxity and patellofemoral dysplasia. Both developed patellar dislocation in adolescence and required surgery, with medial transfer of the tibial tuberosity associated with vastus medialis plasty (Insall technique). One postoperative complication occurred in one case: a nondisplaced tibia fracture at the sixth postoperative week that healed with conservative means. Final results were good in both cases. Good surgical results can be achieved in patellar dislocation in patients with Kabuki syndrome.

Unmasking Kabuki syndrome

The identification of de novo dominant mutations in KMT2D (MLL2) as the main cause of Kabuki syndrome (KS) has shed new light on the pathogenesis of this well-delineated condition consisting of a peculiar facial appearance, short stature, organ malformations and a varying degree of intellectual disability. Mutation screening studies have confirmed KMT2D as the major causative gene for KS and have at the same time provided evidence for its genetic heterogeneity. In this review, we aim to summarize the current clinical and molecular genetic knowledge on KS, provide genotype-phenotype correlations and propose a strategic clinical and molecular diagnostic approach for patients with suspected KS.

Surgical treatment of hip dislocation in Kabuki syndrome: use of incomplete periacetabular osteotomy for posterior acetabular wall deficiency

PURPOSE

Kabuki syndrome is characterized by distinctive facial features, skeletal anomalies, persisting fingertip pads with dermatoglyphic abnormalities, postnatal growth deficiency and mental retardation. This report reviews our results in the operative treatment of hip dislocations in patients with Kabuki syndrome.

METHODS

Between 2001 and 2009, seven dislocated hips (three unilateral and two bilateral hips) in five patients (all girls) were operatively treated at our institution. The operative treatment consists of open reduction, femoral derotation varus osteotomy, pelvic osteotomy (Salter in one and incomplete periacetabular osteotomy in six hips) and capsular plication. The age of the patients at the time of surgery ranged from 2.4 to 5.7 years, with an average of 3.6 years.

RESULTS

The follow-up postoperative period ranged from 3.2 to 6.3 years, with an average of 5.0 years. At the final follow-up, all patients reported no click and no pain, and showed well-contained hips by radiographs. All seven hips were graded as Severin class I-II. One patient presented as having habitual dislocation of the hip 4.4 years after surgery. Computed tomographic (CT) scans revealed posterior acetabular wall deficiency, which was not corrected by the anterolaterally directed Salter osteotomy. The incomplete periacetabular osteotomy provided sufficient posterolateral coverage of the acetabulum.

CONCLUSION

Operative treatment combining open reduction, femoral derotation varus and incomplete periacetabular osteotomies, and capsular plication provided successful results in patients with Kabuki syndrome who had the characteristics of hip instability such as ligamentous laxity, muscular hypotonia and posterior acetabular wall deficiency.

Ectodermal abnormalities in patients with Kabuki syndrome

Kabuki syndrome (KS) is extensively described in the literature and characterized by a typical facial gestalt in combination with postnatal short stature, hypotonia, joint laxity, developmental delay, persistent fetal fingertip pads, and an ever-growing group of congenital abnormalities. In this study, we focus on some ectodermal manifestations that we have observed. We studied seven patients who fulfilled the clinical criteria for KS and undertook a detailed clinical, dental, cytogenetic, and immunoglobulin assessments. In addition, microscopic hair examinations were performed on all patients and compared with matched control patients. All patients had receding of the anterior hair line, but five had evident sparse frontal scalp hair. They all showed peculiar similar microscopic hair abnormalities in the form of twisting of the hair shafts, irregularity of the diameter of the hair, and trichorrhexis nodosa. In addition, hypoplastic nails, café-au-lait patches, and missing upper lateral incisors were observed in 57.1%, 28.6%, and 14.3% of the patients, respectively. Variable orodental anomalies were seen in all the patients with an everted lower lip found in four patients (57.1%). This report provides further evidence that some cases of KS have ectodermal involvement.

Mutation spectrum of MLL2 in a cohort of Kabuki syndrome patients

Background

Kabuki syndrome (Niikawa-Kuroki syndrome) is a rare, multiple congenital anomalies/mental retardation syndrome characterized by a peculiar face, short stature, skeletal, visceral and dermatoglyphic abnormalities, cardiac anomalies, and immunological defects. Recently mutations in the histone methyl transferase MLL2 gene have been identified as its underlying cause.

Methods

Genomic DNAs were extracted from 62 index patients clinically diagnosed as affected by Kabuki syndrome. Sanger sequencing was performed to analyze the whole coding region of the MLL2 gene including intron-exon junctions. The putative causal and possible functional effect of each nucleotide variant identified was estimated by in silico prediction tools.

Results

We identified 45 patients with MLL2 nucleotide variants. 38 out of the 42 variants were never described before. Consistently with previous reports, the majority are nonsense or frameshift mutations predicted to generate a truncated polypeptide. We also identified 3 indel, 7 missense and 3 splice site.

Conclusions

This study emphasizes the relevance of mutational screening of the MLL2 gene among patients diagnosed with Kabuki syndrome. The identification of a large spectrum of MLL2 mutations possibly offers the opportunity to improve the actual knowledge on the clinical basis of this multiple congenital anomalies/mental retardation syndrome, design functional studies to understand the molecular mechanisms underlying this disease, establish genotype-phenotype correlations and improve clinical management.