Kabuki Syndrome

Kabuki Syndrome

Kabuki syndrome (also known as Kabuki make-up syndrome or Niikawa-Kuroki syndrome, OMIM #147920) is a rare genetic disorder characterized by distinctive facial features, skeletal abnormalities, intellectual disability, and multisystem involvement. The name derives from the characteristic facial appearance that resembles the theatrical makeup of Kabuki performers, with long palpebral fissures and eversion of the lower eyelid. First described independently by Japanese physicians Niikawa and Kuroki in 1981, the syndrome has become recognized worldwide as one of the more common rare genetic disorders affecting multiple organ systems. The condition results from heterozygous mutations in genes involved in chromatin remodeling, primarily [KMT2D](/genes/kmt2d) and [KDM6A](/genes/kdm6a), with a combined incidence estimated at 1 in 32,000 to 1 in 86,000 births.

Kabuki Syndrome

Kabuki syndrome (also known as Kabuki make-up syndrome or Niikawa-Kuroki syndrome, OMIM #147920) is a rare genetic disorder characterized by distinctive facial features, skeletal abnormalities, intellectual disability, and multisystem involvement. The name derives from the characteristic facial appearance that resembles the theatrical makeup of Kabuki performers, with long palpebral fissures and eversion of the lower eyelid. First described independently by Japanese physicians Niikawa and Kuroki in 1981, the syndrome has become recognized worldwide as one of the more common rare genetic disorders affecting multiple organ systems. The condition results from heterozygous mutations in genes involved in chromatin remodeling, primarily [KMT2D](/genes/kmt2d) and [KDM6A](/genes/kdm6a), with a combined incidence estimated at 1 in 32,000 to 1 in 86,000 births.

The phenotypic spectrum of Kabuki syndrome demonstrates remarkable variability, ranging from mild presentations with subtle dysmorphic features to severe multisystem involvement affecting growth, development, and organ function[@ng2010]. This clinical heterogeneity, combined with the relatively recent identification of causative genes, has historically made diagnosis challenging. However, advances in molecular genetic testing, particularly whole-exome sequencing, have substantially improved diagnostic accuracy and enabled identification of affected individuals who may have previously gone unrecognized[@lederer2011]. The disorder affects both males and females equally and has been reported across all ethnic backgrounds worldwide, with apparent clustering in Japanese populations where the condition was first described[@white2005].

Pathway / Mechanism Diagram

Overview

Kabuki syndrome is a multisystem developmental disorder caused by heterozygous mutations in genes involved in chromatin remodeling, specifically those encoding components of the [COMPASS complex](/mechanisms/epigenetic-regulation) (Complex of Proteins Associated with Set1) family of histone modifiers[@wu2021]. The condition affects multiple organ systems including the [central nervous system](/brain-regions), cardiovascular system, musculoskeletal system, auditory system, immune system, and endocrine system, resulting in a complex clinical phenotype that requires multidisciplinary care[@matsumoto2003a]. The phenotypic spectrum ranges from mild to severe, with significant interindividual variability even among patients with the same genetic mutation.

The disorder was first described independently by Niikawa and Kuroki in 1981 in Japan, with subsequent identification of the two major causative genes: [KMT2D](/genes/kmt2d) (MLL2) in 2010 and [KDM6A](/genes/kdm6a) (UTX) in 2011[@hannibal2011]. Prior to molecular genetic characterization, diagnosis relied entirely on clinical criteria established by the Japanese Society of Pediatric Endocrinology in 1989 and later modified by Matsumoto and Niikawa in 2003[@matsumoto2003b]. These clinical diagnostic criteria included the five hallmark features: characteristic facial features, skeletal abnormalities, dermatoglyphic abnormalities, intellectual disability, and postnatal growth retardation. While these clinical criteria remain useful for identification of suspected cases, molecular confirmation through genetic testing has become the gold standard for definitive diagnosis[@makrythanasis2013].

The pathophysiology of Kabuki syndrome involves disruption of [epigenetic regulation](/mechanisms/epigenetic-regulation) during embryonic development. The KMT2D and KDM6A genes encode enzymes that modify histone proteins, thereby regulating gene expression patterns critical for normal development. KMT2D functions as a histone H3K4 methyltransferase, adding methyl groups to histone H3 at lysine 4, a modification associated with transcriptional activation[@wu2021a]. KDM6A encodes a histone H3K27 demethylase that removes methyl groups from lysine 27, converting repressive chromatin marks to active ones[@lee2013]. Both enzymes are components of the COMPASS complex that regulates gene expression during development, explaining the widespread multi-system effects observed in affected individuals.

Epidemiology

Kabuki syndrome is estimated to affect approximately 1 in 32,000 to 1 in 86,000 individuals worldwide, though this likely represents an underestimate due to diagnostic challenges and underrecognition of milder phenotypes[@matsumoto2003c]. The wide range in estimated prevalence reflects both geographic variation in detection capabilities and the heterogeneous nature of the disorder. In Japan, where the syndrome was first described and where population-based studies have been conducted, the prevalence is estimated at approximately 1 in 32,000, making Kabuki syndrome one of the more common rare genetic disorders in that population[@niikawa1988].

Both males and females are affected equally, consistent with the autosomal dominant inheritance pattern for KMT2D mutations and the X-linked pattern for most KDM6A mutations[@lederer2011a]. Although initially described primarily in Japanese populations, Kabuki syndrome has now been reported in individuals from all ethnic backgrounds worldwide, including European, North American, South American, African, and Asian populations[@kokitsunakata2015]. The widespread distribution reflects the global nature of the disorder and the availability of molecular diagnostic testing in many countries.

The actual birth prevalence may be higher than currently estimated for several reasons. First, many individuals with mild phenotypic presentations may never receive a formal diagnosis, particularly in regions with limited access to clinical geneticists and genetic testing[@adam2005a]. Second, the clinical overlap with other genetic syndromes can lead to misdiagnosis. Third, the relatively recent identification of KDM6A as a causative gene means that some previously diagnosed cases may have been attributed solely to KMT2D mutations. Population-based studies using genomic data suggest that the true prevalence may be higher than clinical estimates indicate[@chong2015].

Genetics

Kabuki syndrome is caused by heterozygous mutations in genes involved in chromatin remodeling, specifically those encoding components of the [COMPASS complex](/mechanisms/epigenetic-regulation) (Complex of Proteins Associated with Set1) family of histone modifiers[@wu2021b].

Causative Genes

| Gene | Chromosome | Protein | Inheritance | Frequency | Function |
|------|-----------|---------|-------------|-----------|----------|
| [KMT2D](/genes/kmt2d) (MLL2) | 12q13.13 | Lysine N-methyltransferase 2D | Autosomal dominant | ~55-80% of cases | Histone H3K4 methyltransferase |
| [KDM6A](/genes/kdm6a) (UTX) | Xp11.3 | Lysine demethylase 6A | X-linked dominant | ~5-10% of cases | Histone H3K27 demethylase |

[KMT2D](/genes/kmt2d) (also known as MLL2) is the major causative gene for Kabuki syndrome, accounting for approximately 55-80% of molecularly confirmed cases[@banka2015]. The gene encodes a large protein with multiple functional domains, including a SET domain with methyltransferase activity. Over 200 pathogenic variants have been identified, including nonsense mutations, frameshift insertions/deletions, splice site variants, and missense mutations[@lemire2020]. The majority of pathogenic variants are truncating mutations that result in loss of function, consistent with haploinsufficiency as the disease mechanism. Missense mutations are less common but have been identified, particularly in the SET domain and other conserved regions of the protein[@priolo2018].

[KDM6A](/genes/kdm6a) (also known as UTX) accounts for approximately 5-10% of cases and is located on the X chromosome[@lederer2011b]. Unlike classic X-linked disorders, KDM6A-related Kabuki syndrome typically shows an X-linked dominant inheritance pattern, with affected males and females alike. Females can have random X-inactivation patterns that influence disease severity. In males, KDM6A mutations are usually incompatible with survival when inherited in the germline, suggesting that most male cases result from de novo mutations[@banka2015a]. The protein encoded by KDM6A functions as a histone demethylase specific for H3K27me3, a repressive chromatin mark, and plays critical roles in development through regulation of homeobox genes and other key developmental regulators[@ezpert2022].

Genotype-Phenotype Correlations

Studies have identified some genotype-phenotype correlations in Kabuki syndrome, though the clinical variability remains substantial even within mutation categories[@lemire2020a]. Patients with KMT2D mutations tend to have more severe [intellectual disability](/diseases/intellectual-disability-neurodegeneration) and are more likely to have congenital heart defects compared to those with KDM6A mutations[@zhang2022]. Conversely, patients with KDM6A mutations may have a higher frequency of renal abnormalities and hearing loss[@mcdonaldmcginn1993]. These differences likely reflect the distinct functions of these enzymes in gene regulation during development.

Pathophysiology

The pathophysiology of Kabuki syndrome involves disruption of [epigenetic regulation](/mechanisms/epigenetic-regulation) during embryonic and fetal development. The COMPASS family of histone modifiers, of which KMT2D and KDM6A are members, plays critical roles in establishing and maintaining gene expression patterns that direct normal development of multiple organ systems[@wu2021c].

Chromatin Remodeling Mechanisms

KMT2D functions as a histone H3K4 monomethyltransferase, adding a single methyl group to histone H3 at lysine 4[@wu2021d]. This modification is primarily associated with transcriptional activation and is enriched at promoter and enhancer regions of actively transcribed genes. The COMPASS complex containing KMT2D is required for proper development of multiple organs, as demonstrated by mouse models showing that loss of KMT2D function leads to embryonic or perinatal lethality with multiple malformations[@kerenyi2011]. In humans, haploinsufficiency of KMT2D disrupts normal chromatin architecture and gene expression programs during critical periods of organogenesis.

KDM6A (UTX) encodes a histone demethylase that specifically removes the repressive H3K27me3 mark, thereby converting chromatin from a transcriptionally repressed to an active state[@lee2013a]. This enzyme is part of the COMPASS-like complex and works in concert with KMT2D to regulate gene expression. KDM6A is particularly important for the activation of developmental regulator genes, including homeobox genes and other transcription factors that direct cell fate decisions during embryogenesis[@wang2010]. The demethylase activity of KDM6A is essential for proper development of the heart, skeleton, and nervous system.

Downstream Effects

The disruption of epigenetic regulation in Kabuki syndrome leads to abnormal expression of multiple downstream target genes. Studies have identified dysregulation of genes involved in cardiac development (including TBX5, NKX2-5), skeletal development (including HOX genes), neural development, and immune function[@bjornsson2014]. The widespread effects on gene expression explain the multi-system nature of the disorder.

Importantly, the developmental abnormalities in Kabuki syndrome appear to arise primarily from disruption of early developmental processes rather than ongoing dysfunction. This is supported by the observation that many affected individuals show stability or improvement in symptoms over time, rather than progressive deterioration[@adam2005b]. However, some manifestations, such as hearing loss and orthopedic complications, may require ongoing management throughout life.

Clinical Features

Kabuki syndrome affects multiple organ systems, with clinical manifestations ranging from subtle to severe. The hallmark features include distinctive facial dysmorphism, skeletal abnormalities, dermatoglyphic patterns, intellectual disability, and growth retardation[@matsumoto2003d].

Craniofacial and Facial Features

The characteristic facial features of Kabuki syndrome give the condition its name and serve as an important diagnostic clue. The most recognizable features include long palpebral fissures with eversion of the lower lateral eyelid (the "Kabuki" or "make-up" appearance), which is present in over 90% of affected individuals[@adam2005c]. Additional facial features may include arched eyebrows with sparse lateral portions, prominent ears, a broad nasal bridge, a short philtrum, and a characteristic mouth shape with thick lips. The facial features often become more subtle with age, making diagnosis in adulthood more challenging[@armour2018].

Micrognathia (small jaw) is present in approximately 30-40% of patients, and dental anomalies are common, including delayed eruption, hypodontia, and abnormal tooth morphology[@reirre2019]. The palate may be high-arched or cleft, with cleft palate occurring in approximately 30% of cases. These orofacial features can contribute to feeding difficulties in infancy and dental problems throughout life.

Growth and Development

Prenatal and postnatal growth retardation is a hallmark feature of Kabuki syndrome. Prenatal growth failure is common, with many infants born small for gestational age[@armour2018a]. Postnatal growth continues to be delayed, with final adult height often below the third percentile. The growth retardation appears to be multifactorial, involving both prenatal factors and potential growth hormone deficiency in some patients[@masuno1998].

Intellectual disability is present in the majority of patients, though the severity varies widely. Most individuals have mild to moderate intellectual disability, with IQ scores typically ranging from 50 to 80[@adam2005d]. Language development is often delayed, and expressive language skills tend to be more affected than receptive abilities. Behavioral characteristics may include autistic features, attention deficits, and anxiety[@smith2016]. Despite cognitive challenges, many individuals develop functional communication skills and can participate in educational and vocational programs appropriate to their abilities.

Musculoskeletal System

Skeletal abnormalities are present in the majority of patients and include multiple vertebral anomalies (including hemivertebrae, butterfly vertebrae, and scoliosis), rib anomalies, and limb abnormalities[@schranderstumpel1992]. Short fifth fingers (brachydactyly) and clinodactyly of the fifth fingers are common. Joint hypermobility is frequently observed, particularly in early childhood, while later developing joint contractures may affect mobility in some individuals.

Spondyloepiphyseal dysplasia and other skeletal dysplasias have been reported in a subset of patients[@santoro2020]. The vertebral abnormalities can progress during childhood and adolescence, requiring orthopedic monitoring and intervention in some cases. Limb length discrepancies may occur due to asymmetric growth.

Dermatoglyphic Abnormalities

Characteristic dermatoglyphic (fingerprint) patterns are present in over 90% of patients with Kabuki syndrome and are considered a diagnostic hallmark[@matsumoto2003e]. These include excess digital whorls, particularly on the fingertips, and a characteristic pattern of increased digital arch patterns. The fetal pads (dermal ridges) on the fingertips are often elevated and prominent. These dermatoglyphic abnormalities reflect the developmental timing of the genetic disruption and provide a useful diagnostic clue even in the absence of molecular genetic testing.

Cardiovascular System

Congenital heart defects occur in approximately 40-50% of patients with Kabuki syndrome, representing a significant medical concern[@digilio1999]. The most common defects include atrial septal defects, ventricular septal defects, and coarctation of the aorta. Other cardiac anomalies that have been reported include patent ductus arteriosus, pulmonary stenosis, and tetralogy of Fallot[@yuan2017]. Cardiac surgery may be required for significant defects, and lifelong cardiology follow-up is recommended for all patients, even those without structural heart disease, as there may be an increased risk of cardiac arrhythmias.

Central Nervous System

Neurological involvement in Kabuki syndrome includes structural brain abnormalities, seizure disorders, and neurodevelopmental challenges. Structural brain anomalies reported include agenesis of the corpus callosum, cerebellar vermis hypoplasia, and ventriculomegaly[@vaux2005]. Seizures occur in approximately 20-30% of patients and may require antiepileptic medication[@adam2005e]. Hypotonia is common in infancy and may persist into childhood, contributing to delayed motor development.

Auditory System

Hearing loss is a significant concern, affecting approximately 30-40% of patients. The hearing loss can be conductive, sensorineural, or mixed, and may be progressive[@h1993]. Chronic otitis media (ear infections) is common, particularly in young children, and may contribute to conductive hearing loss. Regular audiological evaluation is essential, as hearing loss can impact language development and educational outcomes.

Immune System

Immune dysfunction has been recognized as a component of Kabuki syndrome, with recurrent infections reported in a significant proportion of patients[@hoffman2021]. The immune abnormalities may include reduced immunoglobulin levels, impaired vaccine responses, and increased susceptibility to bacterial and viral infections. Autoimmune phenomena, including autoimmune cytopenias, have been reported in some patients[@lin2022]. The immune dysfunction appears to involve both humoral and cellular immunity and may improve with age in some individuals.

Other System Involvement

Additional system involvement in Kabuki syndrome includes renal anomalies (present in approximately 25-30% of patients, including renal agenesis, horseshoe kidney, and hydronephrosis), gastrointestinal issues (including feeding difficulties, gastroesophageal reflux, and constipation), and endocrine abnormalities (including premature thelarche and adrenal insufficiency)[@mcdonaldmcginn1993a][@chrousos2008]. Endocrine manifestations may require specialized management by pediatric endocrinologists.

Diagnosis

The diagnosis of Kabuki syndrome is established through clinical evaluation combined with molecular genetic testing. The diagnostic approach has evolved significantly since the identification of causative genes, with genetic testing now serving as the primary method for confirming the diagnosis[@mcdonaldmcginn1993b].

Clinical Diagnostic Criteria

Prior to molecular genetic testing, diagnosis relied on clinical criteria established by the Japanese Society of Pediatric Endocrinology in 1989 and modified by Matsumoto and Niikawa in 2003[@matsumoto2003f]. These criteria identified five cardinal features: (1) characteristic facial features, (2) skeletal abnormalities, (3) dermatoglyphic abnormalities, (4) intellectual disability, and (5) postnatal growth retardation. The original criteria required the presence of all five features, while the modified criteria allowed diagnosis with four features in the presence of a characteristic pattern of minor anomalies.

While clinical criteria remain useful for identifying suspected cases, they have limitations. The facial features may be subtle in infancy or become less pronounced with age, and not all patients have all five cardinal features[@armour2018b]. The clinical criteria also do not differentiate between KMT2D-related and KDM6A-related Kabuki syndrome.

Molecular Genetic Testing

Molecular genetic testing for Kabuki syndrome typically begins with sequence analysis of KMT2D and KMT2D (KDM6A), with next-generation sequencing panels or exome sequencing being the most common approaches[@mcdonaldmcginn1993c]. Approximately 55-75% of patients with clinical features of Kabuki syndrome will have a pathogenic variant identified in one of these two genes. The detection rate varies depending on the clinical severity and completeness of testing.

The identification of a pathogenic variant in either KMT2D or KDM6A confirms the diagnosis of Kabuki syndrome and enables accurate genetic counseling for the family. If no pathogenic variant is identified in either gene, the diagnosis of Kabuki syndrome may still be considered based on clinical features, as there may be as-yet unidentified causative genes[@adam2005f]. Family testing for known pathogenic variants is recommended to identify potentially affected relatives and inform recurrence risk counseling.

Differential Diagnosis

The differential diagnosis for Kabuki syndrome includes other genetic disorders with overlapping clinical features. The differential diagnosis includes, but is not limited to: CHARGE syndrome (coloboma, heart defects, atresia choanae, growth retardation, ear abnormalities), 22q11.2 deletion syndrome (DiGeorge/velo-cardio-facial syndrome), and other chromatin remodeling disorders such as Weaver syndrome (EZH2 mutations) and Kleefstra syndrome (EHMT1 mutations)[@mcdonaldmcginn1993d]. Careful clinical evaluation and molecular genetic testing help distinguish between these conditions.

Treatment/Management

There is no cure for Kabuki syndrome, and treatment is focused on managing the specific manifestations and improving quality of life. Management requires a multidisciplinary team approach involving genetics, cardiology, neurology, developmental pediatrics, orthopedics, audiology, ophthalmology, and other specialists as needed[@mcdonaldmcginn1993e].

Developmental and Educational Interventions

Early intervention services are critical for maximizing developmental outcomes. Physical therapy, occupational therapy, and speech-language therapy should be initiated in early childhood and continued as needed based on individual progress[@adam2005g]. Special education services and individualized education plans (IEPs) are often necessary to address learning disabilities and developmental delays. Behavioral interventions may be helpful for managing autistic features, attention deficits, and anxiety.

Medical Management

Medical management of Kabuki syndrome addresses the specific manifestations present in each individual. Regular cardiology follow-up, including echocardiography, is recommended to monitor for congenital heart defects and arrhythmias[@digilio1999a]. Surgical repair of significant cardiac defects may be required. Orthopedic management may include bracing or surgical intervention for scoliosis, vertebral anomalies, and other skeletal problems.

Hearing loss requires prompt evaluation and management, including hearing aids when appropriate. Surgical correction of cleft palate and other orofacial anomalies may be indicated. Endocrine evaluation and management of growth failure or premature puberty may require consultation with a pediatric endocrinologist[@chrousos2008a].

Supportive Care

Supportive care for Kabuki syndrome includes nutritional support for feeding difficulties, management of gastrointestinal issues, and immunological monitoring. Regular monitoring of growth and development using standardized growth charts and developmental assessments is essential. Genetic counseling for the family is important to discuss recurrence risks and family planning options.

Prognosis

The prognosis for individuals with Kabuki syndrome varies depending on the severity of manifestations and the availability of appropriate medical care and developmental interventions. With early diagnosis and comprehensive management, many individuals can achieve meaningful developmental progress and lead fulfilling lives[@armour2018c].

Life Expectancy

Life expectancy is generally normal for individuals with Kabuki syndrome who do not have severe congenital heart defects or other life-threatening medical conditions. The majority of individuals survive into adulthood, though comprehensive medical care and monitoring are typically required throughout life[@mcdonaldmcginn1993f].

Quality of Life

Quality of life can be optimized through early intervention, appropriate educational support, and management of medical complications. Many adults with Kabuki syndrome are able to achieve varying degrees of independence, with some living semi-independently with support services. Social integration and quality of life are enhanced by early intervention, family support, and access to appropriate services[@adam2005h].

Current Research

Research on Kabuki syndrome continues to advance understanding of the disorder and identify potential therapeutic approaches. Current research directions include natural history studies, genotype-phenotype correlation analyses, and investigation of potential molecular therapies.

Clinical Research

Natural history studies are ongoing to better characterize the long-term outcomes and medical needs of individuals with Kabuki syndrome[@armour2018d]. These studies aim to identify predictors of outcome and inform management guidelines. Genotype-phenotype correlation studies continue to refine understanding of how different mutations influence the clinical presentation.

Basic Science Research

Basic science research is focused on understanding the molecular mechanisms underlying Kabuki syndrome and identifying potential therapeutic targets. Studies using patient-derived cells and animal models are investigating how KMT2D and KDM6A dysfunction leads to the observed developmental abnormalities[@wu2021e]. Epigenetic therapies targeting the COMPASS complex are under investigation, though clinical applications remain experimental.

Differential Diagnosis

The differential diagnosis for Kabuki syndrome includes other genetic conditions with overlapping features. Key conditions to consider include CHARGE syndrome (CHD7 mutations), 22q11.2 deletion syndrome, and other disorders of chromatin remodeling such as Weaver syndrome (EZH2 mutations), Kleefstra syndrome (EHMT1 mutations), and Rubinstein-Taybi syndrome (CREBBP, EP300 mutations)[@mcdonaldmcginn1993g].

CHARGE syndrome shares some features with Kabuki syndrome, including coloboma, heart defects, hearing loss, and developmental delay. However, CHARGE syndrome typically includes choanal atresia, which is not a feature of Kabuki syndrome, and the facial features are distinct[@blake1995].

22q11.2 deletion syndrome (DiGeorge/velo-cardio-facial syndrome) includes cardiac anomalies, immune deficiency, hypocalcemia, and characteristic facial features. Molecular testing for 22q11.2 deletion should be considered in patients with appropriate clinical features[@mcdonaldmcginn1999].

Weaver syndrome, caused by EZH2 mutations, shares features of overgrowth, intellectual disability, and characteristic facial features with Kabuki syndrome. Molecular testing can distinguish between these conditions.

Animal Models

Animal models of Kabuki syndrome have been developed to study the pathophysiology of the disorder and test potential therapies. Mouse models with heterozygous loss-of-function mutations in Kmt2d have been generated and show phenotypic features resembling human Kabuki syndrome, including growth retardation, craniofacial abnormalities, and learning deficits[@wang2016].

Zebrafish models have also been developed, providing a system for high-throughput drug screening and studies of developmental mechanisms[@liu2021]. These models demonstrate that loss of Kmt2d or Kdm6a function disrupts normal development of multiple organ systems, consistent with the human phenotype.

Studies in animal models have confirmed that the developmental abnormalities in Kabuki syndrome result from disruption of epigenetic regulation during embryonic development rather than ongoing dysfunction. This has important implications for therapeutic approaches, suggesting that early intervention may be most effective.

See Also

• [KMT2D](/genes/kmt2d)
• [KDM6A](/genes/kdm6a)
• [COMPASS complex](/mechanisms/epigenetic-regulation)
• [epigenetic regulation](/mechanisms/epigenetic-regulation)
• [intellectual disability](/diseases/intellectual-disability-neurodegeneration)

External Links

• [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
• [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)

References