[Clinical and genetic characteristics of four children with Kabuki syndrome due to de novo variants of KMT2D gene].

OBJECTIVE: To explore the clinical and genetic characteristics of four children with Kabuki syndrome (KS) due to variants of KMT2D gene. METHODS: Four children with KS diagnosed at the Children's Hospital of Shanxi Province between January 2020 and December 2022 were selected as the study subjects. Whole exome sequencing was carried out for the children and their family members. Candidate variants were verified by Sanger sequencing and pathogenicity analysis. RESULTS: The KS phenotype scores for the four children were 7, 8, 6, and 6, respectively. Child 2 also presented with a rare solitary kidney malformation. Genetic testing revealed that all children had harbored novel de novo variants of the KMT2D gene, including c.16472_16473del, c.858dup, c.11899C>T, and c.12844C>T, respectively. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), all of the variants were classified as pathogenic. CONCLUSION: For children showing phenotypes such as distinctive facial features, intellectual disability, developmental delay, cardiac abnormalities, and urinary system anomalies, KS should be considered. Early diagnosis and intervention can be achieved through genetic testing, especially in the presence of KMT2D gene mutations.

Autoimmune cytopenia and Kabuki syndrome in paediatrics: Insights in 11 patients.

Kabuki syndrome (KS) is now listed in the Human Inborn Errors of Immunity (IEI) Classification. It is a rare disease caused by KMT2D and KDM6A variants, dominated by intellectual disability and characteristic facial features. Recurrently, pathogenic variants are identified in those genes in patients examined for autoimmune cytopenia (AIC), but interpretation remains challenging. This study aims to describe the genetic diagnosis and the clinical management of patients with paediatric-onset AIC and KS. Among 11 patients with AIC and KS, all had chronic immune thrombocytopenic purpura, and seven had Evans syndrome. All had other associated immunopathological manifestations, mainly symptomatic hypogammaglobinaemia. They had a median of 8 (5-10) KS-associated manifestations. Pathogenic variants were detected in KMT2D gene without clustering, during the immunological work-up of AIC in three cases, and the clinical strategy to validate them is emphasized. Eight patients received second-line treatments, mainly rituximab and mycophenolate mofetil. With a median follow-up of 17 (2-31) years, 8/10 alive patients still needed treatment for AIC. First-line paediatricians should be able to recognize and confirm KS in children with ITP or multiple AIC, to provide early appropriate clinical management and specific long-term follow-up. The epigenetic immune dysregulation in KS opens exciting new perspectives.

Craniosynostosis in molecularly diagnosed Kabuki syndrome: Prevalence and clinical implications.

Kabuki syndrome (KS) is characterized by growth impairment, psychomotor delay, congenital heart disease, and distinctive facial features. KMT2D and KDM6A have been identified as the causative genes of KS. Craniosynostosis (CS) has been reported in individuals with KS; however, its prevalence and clinical implications remain unclear. In this retrospective study, we investigated the occurrence of CS in individuals with genetically diagnosed KS and examined its clinical significance. Among 42 individuals with genetically diagnosed KS, 21 (50%) exhibited CS, with 10 individuals requiring cranioplasty. No significant differences were observed based on sex, causative gene, and molecular consequence among individuals with KS who exhibited CS. Both individuals who underwent evaluation with three-dimensional computed tomography (3DCT) and those who required surgery tended to exhibit cranial dysmorphology. Notably, in several individuals, CS was diagnosed before KS, suggesting that CS could be one of the clinical features by which clinicians can diagnose KS. This study highlights that CS is one of the noteworthy complications in KS, emphasizing the importance of monitoring cranial deformities in the health management of individuals with KS. The findings suggest that in individuals where CS is a concern, conducting 3DCT evaluations for CS and digital impressions are crucial.

[Congenital hyperinsulinism as a part of Kabuki syndrome].

Kabuki syndrome is a rare hereditary disease characterized by distinctive facial features, skeletal abnormalities, mental retardation, developmental delay, and anomalies in multiple organ systems development.Congenital hyperinsulinism is a rare manifestation of his Kabuki syndrome. However, early diagnosis is crucial to prevent neurological complications of hypoglycemia.There are 2 types of Kabuki Syndrome depending on severity of symptoms. Kabuki syndrome Type 1 is associated with heterozygous mutations in gene KMT2D. Kabuki syndrome Type 2 is inherited in an X-linked manner. It's associated with heterozygous mutations in gene KDM6A and characterized by more severe course of the disease.This paper presents 2 cases of children with congenital hyperinsulinism as the feature of Kabuki syndrome Type 1 and Type 2.

Systemic Presentation of Somatic TET2 Mutated B-Cell Lymphoma in a Child With Kabuki Syndrome and a Germline KMT2D Variant.

OBJECTIVES: Kabuki syndrome (KS) is a rare congenital malformation syndrome associated with germline KMT2D mutations. Recurrent somatic mutations in KMT2D have frequently been observed in B-cell lymphoma, but limited studies are available that evaluate the genetic landscape of B-cell lymphomas in the setting of KS. METHODS: We describe a unique case of B-cell lymphoma that illustrates histologic features of pediatric-type follicular lymphoma (FL) in a young patient with KS and autoimmune disease who showed a systemic presentation of widespread lymphadenopathy and clonal lymphocytosis. RESULTS: We present the first reported case of a young patient with KS harboring a germline KMT2D variant and presenting with a systemic CD10-positive, BCL2-negative B-cell lymphoma of follicle center origin illustrating histologic features of pediatric-type FL. Targeted next-generation sequencing of the B-cell lymphoma showed somatic TET2 and subclonal CXCR4 variants. These findings suggest that abnormal epigenetic regulation caused by alterations in KMT2D and TET2 may have played critical roles in promoting lymphomagenesis in this patient. CONCLUSIONS: This unique case presentation highlights the importance of close clinical monitoring and the value of clinical context in the diagnosis of pediatric FL-like lesions in patients with KS.

Comparison of methylation episignatures in KMT2B- and KMT2D-related human disorders.

Aim & methods: To investigate peripheral blood methylation episignatures in KMT2B-related dystonia (DYT-KMT2B), the authors undertook genome-wide methylation profiling of ∼2 M CpGs using a next-generation sequencing-based assay and compared the findings with those in controls and patients with KMT2D-related Kabuki syndrome type 1 (KS1). Results: A total of 1812 significantly differentially methylated CpG positions (false discovery rate < 0.05) were detected in DYT-KMT2B samples compared with controls. Multi-dimensional scaling analysis showed that the 10 DYT-KMT2B samples clustered together and separately from 29 controls and 10 with pathogenic variants in KMT2D. The authors found that most differentially methylated CpG positions were specific to one disorder and that all (DYT-KMT2B) and most (Kabuki syndrome type 1) methylation alterations in CpG islands were gain of methylation events. Conclusion: Using sensitive methylation profiling methodology, the authors replicated recent reports of a methylation episignature for DYT-KMT2B. These findings will facilitate the development of episignature-based assays to improve diagnostic accuracy.

The authors compared the DNA methylation patterns in blood from individuals with two rare neurodevelopmental disorders (childhood-onset dystonia [DYT-KMT2B] and Kabuki syndrome type 1) and healthy control samples. These two disorders are associated with pathogenic variants in KMT2B and KMT2D, which encode proteins with related functions but cause distinct inherited disorders. Comparison of the methylation patterns in the two disorders showed that most DNA regions with altered methylation patterns differed between the two disorders and controls. These findings suggest that analyzing DNA methylation patterns could improve diagnostic testing for these disorders and might provide insights into how the clinical features of these disorders are caused.

A Patient with Kabuki Syndrome Mutation Presenting with Very Severe Aplastic Anemia.

Kabuki syndrome (KS) is a rare congenital disorder commonly complicated by humoral immunodeficiency. Patients with KS present with mutation in the histone-lysine N-methyltransferase 2D (KMT2D) gene. Although various KMT2D mutations are often identified in lymphoma and leukemia, those encountered in aplastic anemia (AA) are limited. Herein, we present the case of a 45-year-old Japanese man who developed severe pancytopenia and hypogammaglobulinemia. He did not present with any evident malformations, intellectual disability, or detectable levels of autoantibodies. However, B-cell development was impaired. Therefore, a diagnosis of very severe AA due to a hypoplastic marrow, which did not respond to granulocyte colony-stimulating factor, was made. The patient received umbilical cord blood transplantation but died from a Pseudomonas infection before neutrophil engraftment. Trio whole-exome sequencing revealed a novel missense heterozygous mutation c.15959G >A (p.R5320H) in exon 50 of the KMT2D gene. Moreover, Sanger sequencing of peripheral blood and bone marrow mononuclear cells and a skin biopsy specimen obtained from this patient identified this heterozygous mutation, suggesting that de novo mutation associated with KS occurred in the early embryonic development. Our case showed a novel association between KS mutation and adult-onset AA.

Lysine methyltransferase 2D regulates muscle fiber size and muscle cell differentiation.

Kabuki syndrome (KS) is a rare genetic disorder caused primarily by mutations in the histone modifier genes KMT2D and KDM6A. The genes have broad temporal and spatial expression in many organs, resulting in complex phenotypes observed in KS patients. Hypotonia is one of the clinical presentations associated with KS, yet detailed examination of skeletal muscle samples from KS patients has not been reported. We studied the consequences of loss of KMT2D function in both mouse and human muscles. In mice, heterozygous loss of Kmt2d resulted in reduced neuromuscular junction (NMJ) perimeter, decreased muscle cell differentiation in vitro and impaired myofiber regeneration in vivo. Muscle samples from KS patients of different ages showed presence of increased fibrotic tissue interspersed between myofiber fascicles, which was not seen in mouse muscles. Importantly, when Kmt2d-deficient muscle stem cells were transplanted in vivo in a physiologic non-Kabuki environment, their differentiation potential is restored to levels undistinguishable from control cells. Thus, the epigenetic changes due to loss of function of KMT2D appear reversible through a change in milieu, opening a potential therapeutic avenue.

Neuroimaging in Kabuki syndrome and another KMT2D-related disorder.

Recognition of distinct phenotypic features is an important component of genetic diagnosis. Although CHARGE syndrome, Kabuki syndrome, and a recently delineated KMT2D Ex 38/39 allelic disorder exhibit significant overlap, differences on neuroimaging may help distinguish these conditions and guide genetic testing and variant interpretation. We present an infant clinically diagnosed with CHARGE syndrome but subsequently found to have a de novo missense variant in exon 38 of KMT2D, the gene implicated in both Kabuki syndrome and a distinct KMT2D allelic disorder. We compare her brain and inner ear morphology to a retrospective cohort of 21 patients with classic Kabuki syndrome and to typical CHARGE syndrome findings described in the literature. Thirteen of the 21 Kabuki syndrome patients had temporal bone imaging (5/13 CT, 12/13 MRI) and/or brain MRI (12/13) which revealed findings distinct from both CHARGE syndrome and the KMT2D allelic disorder. Our findings further elucidate the spectrum of inner ear dysmorphology distinguishing Kabuki syndrome and the KMT2D allelic disorder from CHARGE syndrome, suggesting that these three disorders may be differentiated at least in part by their inner ear anomalies.

Ophthalmic manifestations in Kabuki (make-up) syndrome: A single-center pediatric cohort and systematic review of the literature.

Kabuki syndrome (KS) is a genetic disorder caused by pathogenic variants in KMT2D or KDM6A, and manifesting with multi-systemic involvement, including recognizable facial features, developmental delay and multiple congenital anomalies. Ophthalmological involvement has been described in varying rates in several studies. We aimed to evaluate the prevalence and nature of ophthalmological findings in a cohort of KS patients in Israel. Medical records of all patients diagnosed with KS in our tertiary center between 2004 and 2020 were retrospectively reviewed. Data collected included physical examination findings, molecular analysis as well as comprehensive ophthalmic characteristics including visual acuity, ocular alignment and motility, ocular adnexa, anterior segments and dilated fundus exams. Finally, an updated systematic review of the literature was performed. Thirteen unrelated patients were included in the study, diagnosed at an age raging from the first months of life to 20 years. Of these, three (23%) showed significant ophthalmological abnormalities, beyond the characteristic structural findings of long palpebral fissures and lower eyelid eversion. These included bilateral posterior colobomata in the first patient; bilateral ptosis, hypermetropia, esotropia, blue sclera and anisocoria in the second; and bilateral congenital cataracts in the third. To conclude, our findings underscore the importance of a comprehensive ophthalmological evaluation as part of the routine multidisciplinary assessment of children suspected/diagnosed with KS.

Generation and characterization of a P2rx2 V60L mouse model for DFNA41.

P2RX2 encodes the P2X2 receptor, which is an adenosine triphosphate (ATP) gated (purinoreceptor) ion channel. P2RX2 c. 178G > T (p.V60L) mutation was previously identified in two unrelated Chinese families, as the cause of human DFNA41, a form of dominant, early-onset and progressive sensorineural hearing loss. We generated and characterized a knock-in mouse model based on human p.V60L mutation that recapitulates the human phenotype. Heterozygous KI mice started to exhibit hearing loss at 21-day-old and progressed to deafness by 6-month-old. Vestibular dysfunction was also observed in mutant mice. Abnormal morphology of the inner hair cells and ribbon synapses was progressively observed in KI animals suggesting that P2rx2 plays a role in the membrane spatial location of the ribbon synapses. These results suggest that P2rx2 is essential for acoustic information transfer, which can be the molecular mechanism related to hearing loss.

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.

Progressive Massive Splenomegaly in an Adult Patient with Kabuki Syndrome Complicated with Immune Thrombocytopenic Purpura.

Kabuki syndrome is characterized by multiple systemic anomalies and intellectual disability. It is complicated with immunodeficiencies and autoimmune disorders. The syndrome is caused by a mutation in the KMT2D gene. We herein report a case of a Kabuki syndrome with developing immune thrombocytopenic purpura (ITP) and progressive splenomegaly. Laparoscopic splenectomy was performed and the patients' symptoms quickly disappeared with platelet recovery. After this operation, the patient had no severe complications. A sequence analysis of the KMT2D gene identified a pathogenic mutation frequently associated with ITP. Laparoscopic splenectomy is therefore considered to be a good therapeutic option for recurrent ITP and symptomatic splenomegaly with Kabuki syndrome.

Autoimmune Cytopenias and Dysregulated Immunophenotype Act as Warning Signs of Inborn Errors of Immunity: Results From a Prospective Study.

Inborn errors of immunity (IEI) are genetic disorders characterized by a wide spectrum of clinical manifestations, ranging from increased susceptibility to infections to significant immune dysregulation. Among these, primary immune regulatory disorders (PIRDs) are mainly presenting with autoimmune manifestations, and autoimmune cytopenias (AICs) can be the first clinical sign. Significantly, AICs in patients with IEI often fail to respond to first-line therapy. In pediatric patients, autoimmune cytopenias can be red flags for IEI. However, for these cases precise indicators or parameters useful to suspect and screen for a hidden congenital immune defect are lacking. Therefore, we focused on chronic/refractory AIC patients to perform an extensive clinical evaluation and multiparametric flow cytometry analysis to select patients in whom PIRD was strongly suspected as candidates for genetic analysis. Key IEI-associated alterations causative of STAT3 GOF disease, IKAROS haploinsufficiency, activated PI3Kδ syndrome (APDS), Kabuki syndrome and autoimmune lymphoproliferative syndrome (ALPS) were identified. In this scenario, a dysregulated immunophenotype acted as a potential screening tool for an early IEI diagnosis, pivotal for appropriate clinical management and for the identification of new therapeutic targets.

A Rare Cause of Hyperinsulinemic Hypoglycemia: Kabuki Syndrome

Kabuki syndrome (KS) is a disease characterized by distinctive facial features, skeletal anomalies and delay in neuromotor development. KS 1 is an autosomal dominant condition caused by mutations in the KMT2D gene, whereas KS 2 is an X-linked disorder caused by mutations in the KDM6A gene. In the majority of KS patients who present with hypoglycemia, KDM6A is the defective gene. A 9-month old girl was admitted to our emergency department due to a seizure. On physical examination, hypotonia, mild facial dysmorphism, brachydactyly of the 5th finger, prominent finger pads and pansystolic murmur were detected. A fasting glucose tolerance test was performed the next day due to her history of hypoglycemia, but she had convulsions at the fifth hour of the test. Her serum glucose was 24 mg/dL, insulin 1.94 mIU/L, C-peptide 0.94 ng/mL, growth hormone 11 ng/mL, anti-insulin antibody 4.2 IU/mL, cortisol 19.8 µg/dL, and adrenocorticotropic hormone 9.3 pg/mL. A diagnosis of hyperinsulinemic hypoglycemia was considered. Given the abnormalities, genetic analysis for congenital hyperinsulinism, including the genes causing KS was performed. A heterozygous frameshift mutation (c.2579del, p.Leu860Argfs*70) was detected in the KMT2D gene. Epilepsy and other neurological symptoms may be seen in KS patients and in some of these the neurological symptoms are the result of hypoglycemia. In such cases, the detection and prevention of hypoglycemia can help prevent the progression of neurological symptoms. We suggest considering the diagnosis of KS for patients with hypoglycemia and dysmorphic features, even if the patient does not manifest all features of KS.

Clinical and molecular characterization study of Chinese Kabuki syndrome in Hong Kong.

Kabuki syndrome (OMIM #147920 and 300867) is a rare genetic disorder characterized by a distinctive facial gestalt, intellectual disability and multiple congenital anomalies. We summarized the clinical features and molecular findings of the Kabuki syndrome (KS) patients diagnosed in Hong Kong between January 1991 and December 2019. There were 21 molecularly confirmed KS. Twenty of them were due to pathogenic KMT2D variants and one patient had KDM6A deletion. Nine KMT2D variants were novel. The clinical phenotype of our Chinese KS patients was largely comparable with that reported in patients of other ethnicities. This study expands the mutation spectrum but also provide important natural history information of Chinese KS in literature.

MLL4-associated condensates counterbalance Polycomb-mediated nuclear mechanical stress in Kabuki syndrome.

The genetic elements required to tune gene expression are partitioned in active and repressive nuclear condensates. Chromatin compartments include transcriptional clusters whose dynamic establishment and functioning depend on multivalent interactions occurring among transcription factors, cofactors and basal transcriptional machinery. However, how chromatin players contribute to the assembly of transcriptional condensates is poorly understood. By interrogating the effect of KMT2D (also known as MLL4) haploinsufficiency in Kabuki syndrome, we found that mixed lineage leukemia 4 (MLL4) contributes to the assembly of transcriptional condensates through liquid-liquid phase separation. MLL4 loss of function impaired Polycomb-dependent chromatin compartmentalization, altering the nuclear architecture. By releasing the nuclear mechanical stress through inhibition of the mechanosensor ATR, we re-established the mechanosignaling of mesenchymal stem cells and their commitment towards chondrocytes both in vitro and in vivo. This study supports the notion that, in Kabuki syndrome, the haploinsufficiency of MLL4 causes an altered functional partitioning of chromatin, which determines the architecture and mechanical properties of the nucleus.

Hypoglycemia and Dandy-Walker variant in a Kabuki syndrome patient: a case report.

BACKGROUND: Kabuki syndrome (KS) is a rare congenital condition with cardinal manifestations of typical facial features, developmental delays, skeletal anomalies, abnormal dermatoglyphic presentations, and mild to moderate intellectual disability. Pathogenic variants in two epigenetic modifier genes, KMT2D and KDM6A, are responsible for KS1 and KS2, respectively. CASE PRESENTATION: A Chinese girl had persistent neonatal hypoglycemia and Dandy-Walker variant. Whole-exome sequencing identified a novel single nucleotide deletion in KMT2D (NM_003482.3 c.12165del p.(Glu4056Serfs*10)) that caused frameshift and premature termination. The mutation was de novo. According to the American College of Medical Genetics and Genomics (ACMG) guidelines, this variant is considered pathogenic. The patient was diagnosed with KS by molecular testing. CONCLUSION: A single novel mutation in KMT2D was identified in a KS patients with hypoglycemia and Dandy-Walker variant in the neonatal stage. A molecular test was conducted to diagnose KS at an early stage.

Neonatal hyperinsulinemic hypoglycemia: case report of kabuki syndrome due to a novel KMT2D splicing-site mutation.

BACKGROUND: Persistent neonatal hypoglycemia, owing to the possibility of severe neurodevelopmental consequences, is a leading cause of neonatal care admission. Hyperinsulinemic hypoglycemia is often resistant to dextrose infusion and needs rapid diagnosis and treatment. Several congenital conditions, from single gene defects to genetic syndromes should be considered in the diagnostic approach. Kabuki syndrome type 1 (MIM# 147920) and Kabuki syndrome type 2 (MIM# 300867), can be associated with neonatal hyperinsulinemic hypoglycemia. PATIENT PRESENTATION: We report a female Italian (Sicilian) child, born preterm at 35 weeks gestation, with persistent hypoglycemia. Peculiar facial dysmorphisms, neonatal hypotonia, and cerebellar vermis hypoplasia raised suspicion of Kabuki syndrome. Hyperinsulinemic hypoglycemia was confirmed with glucagon test and whole-exome sequencing (WES) found a novel heterozygous splicing-site mutation (c.674-1G > A) in KMT2D gene. Hyperinsulinemic hypoglycemia was successfully treated with diazoxide. At 3 months corrected age for prematurity, a mild global neurodevelopmental delay, postnatal weight and occipitofrontal circumference growth failure were reported. CONCLUSIONS: Kabuki syndrome should be considered when facing neonatal persistent hypoglycemia. Diazoxide may help to improve hyperinsulinemic hypoglycemia. A multidisciplinary and individualized follow-up should be carried out for early diagnosis and treatment of severe pathological associated conditions.

Update of the genotype and phenotype of KMT2D and KDM6A by genetic screening of 100 patients with clinically suspected Kabuki syndrome.

Kabuki syndrome is characterized by a variable degree of intellectual disability, characteristic facial features, and complications in various organs. Many variants have been identified in two causative genes, that is, lysine methyltransferase 2D (KMT2D) and lysine demethylase 6A (KDM6A). In this study, we present the results of genetic screening of 100 patients with a suspected diagnosis of Kabuki syndrome in our center from July 2010 to June 2018. We identified 76 variants (43 novel) in KMT2D and 4 variants (3 novel) in KDM6A as pathogenic or likely pathogenic. Rare variants included a deep splicing variant (c.14000-8C>G) confirmed by RNA sequencing and an 18% mosaicism level for a KMT2D mutation. We also characterized a case with a blended phenotype consisting of Kabuki syndrome, osteogenesis imperfecta, and 16p13.11 microdeletion. We summarized the clinical phenotypes of 44 patients including a patient who developed cervical cancer of unknown origin at 16 years of age. This study presents important details of patients with Kabuki syndrome including rare clinical cases and expands our genetic understanding of this syndrome, which will help clinicians and researchers better manage and understand patients with Kabuki syndrome they may encounter.