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1
Inheritance
8
Pathophys.
27
Phenotypes
3
Hypotheses
23
Pathograph
1
Genes
4
Medical Actions
6
References
1
Deep Research
👪

Inheritance

1
Autosomal dominant inheritance HP:0000006
Arboleda-Tham syndrome is autosomal dominant and is almost always caused by a de novo heterozygous pathogenic KAT6A variant.
Autosomal dominant inheritance Penetrance: COMPLETE Expressivity: VARIABLE
Show evidence (1 reference)
PMID:25728775 SUPPORT Human Clinical
"Here, we report a syndrome caused by de novo heterozygous nonsense mutations in KAT6A (a.k.a., MOZ, MYST3) identified by clinical exome sequencing (CES) in four independent families."
The founding series establishes heterozygous, de novo KAT6A variants as the cause, consistent with autosomal dominant inheritance.

Mechanistic Hypotheses

3
Early-Truncating NMD / Haploinsufficiency Branch
early_truncating_nmd_haploinsufficiency CANONICAL
Evidence balance 1 support
Truncating variants in exons 1-15 are predicted to trigger nonsense-mediated decay of the mutant transcript, producing KAT6A haploinsufficiency. This branch is associated with a milder phenotype, with a majority of early-truncating cases rated as having mild intellectual disability.
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"This suggests a potential role for nonsense mediated decay (NMD), where truncating mutations in the first 15 exons trigger NMD mechanisms and result in haploinsufficiency while mutations in exons 16 and 17 would not result in NMD, therefore the mRNA would result in a translated but dysfunctional..."
The genotype-phenotype study proposes NMD-mediated haploinsufficiency for early-truncating variants as the basis for milder disease.
Late-Truncating NMD-Escape Branch
late_truncating_nmd_escape ALTERNATIVE
Evidence balance 1 support
Truncating variants in the last two exons (16-17) escape nonsense-mediated decay and are predicted to yield a translated but dysfunctional protein with possible gain-of-function or dominant-negative effects. This branch is associated with more severe developmental delay and a higher frequency of several syndromic features. Direct demonstration of mutant protein and its mode of action in patient tissue remains an evidence gap.
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"95% of late truncating cases (exon 16 and 17) were rated as moderate or severe, while 60% of early truncating cases (exons 1-15) were rated as mild"
The cohort documents the more severe developmental phenotype associated with the NMD-escaping late-truncating branch.
KAT6A-RSPO2-Wnt Hippocampal Signaling Branch
kat6a_rspo2_wnt_hippocampal EMERGING
Evidence balance 1 support
An emerging mechanism, so far demonstrated only in mice, links KAT6A deficiency to impaired cognition through a specific transcriptional target: KAT6A activates the CA3-enriched Wnt activator R-spondin 2 (RSPO2), and its loss reduces hippocampal CA3 synaptic structure, plasticity, and Wnt signaling. Restoring RSPO2 in CA3 neurons rescues Wnt signaling and learning behaviors in Kat6a mutant mice, nominating the KAT6A-RSPO2-Wnt axis as a candidate therapeutic target. Fidelity to human KAT6A-syndrome cognition is not yet established.
Show evidence (1 reference)
PMID:38758792 SUPPORT Model Organism
"Collectively, our results demonstrate that KAT6A-RSPO2-Wnt signaling plays a critical role in regulating hippocampal CA3 synaptic plasticity and cognitive function, providing potential therapeutic targets for KAT6A syndrome and related neurodevelopmental diseases."
A mouse study defines the KAT6A-RSPO2-Wnt hippocampal axis as an emerging mechanism of the cognitive phenotype and a candidate therapeutic target.

Pathophysiology

8
Heterozygous KAT6A Pathogenic Variation
The initiating lesion is a heterozygous, usually de novo, pathogenic KAT6A variant. Most established alleles are protein-truncating (nonsense or frameshift), with recurrent hotspots in the arginine-rich acidic domain, and are distributed across the gene with a bias toward the last two exons.
KAT6A hgnc:13013
Show evidence (1 reference)
PMID:25728777 SUPPORT Human Clinical
"All five different de novo heterozygous truncating mutations were located in the C-terminal transactivation domain of KAT6A"
The founding series establishes heterozygous, de novo truncating KAT6A variants clustered in the C-terminal domain.
NMD-Mediated KAT6A Haploinsufficiency
Early-truncating variants (exons 1-15) are predicted to trigger nonsense-mediated decay of the mutant transcript, reducing functional KAT6A dosage (haploinsufficiency). This is the canonical route and is associated with milder disease.
NMD-Escaping Dysfunctional KAT6A Protein
Late-truncating variants (exons 16-17) escape nonsense-mediated decay and are predicted to produce a translated but dysfunctional protein that may act by gain-of-function or dominant-negative mechanisms. This is the alternative route and is associated with more severe disease. Direct demonstration of mutant protein and its mode of action in patient tissue remains an evidence gap.
Dysregulated Histone H3 Acetylation
KAT6A (MOZ/MYST3) is a MYST-family histone acetyltransferase that, within a complex containing BRPF1/2/3, ING5, and hEAF6, acetylates lysine residues on histone H3 tails (notably H3K9 and H3K18). Pathogenic variants dysregulate H3K9 and H3K18 acetylation, altering the chromatin state that governs developmental gene expression. (GO lacks a current, non-obsolete histone-H3-specific acetylation biological-process term; the H3 specificity is carried by the H3K9 and H3K18 molecular-function annotations.)
chromatin organization GO:0006325 ⚠ ABNORMAL
histone acetyltransferase activity GO:0004402 histone H3K9 acetyltransferase activity GO:0043992 ↕ DYSREGULATED histone H3K18 acetyltransferase activity GO:0043993 ↕ DYSREGULATED
Show evidence (2 references)
PMID:25728775 SUPPORT In Vitro
"We further demonstrate that KAT6A mutations result in dysregulation of H3K9 and H3K18 acetylation and altered P53 signaling."
Directly supports dysregulated H3K9/H3K18 acetylation as the molecular consequence of KAT6A mutation.
PMID:30245513 SUPPORT Other
"KAT6A and KAT6B each function in a multi-subunit complex with three other proteins: BRPF1/2/3, ING5 and hEAF6"
Establishes the KAT6A histone-acetyltransferase complex through which the enzyme acts on histone H3.
Altered p53 Signaling
Beyond its direct catalytic effect on histone H3, KAT6A dysfunction perturbs p53-associated transcriptional programs. Patient-derived fibroblasts show altered expression of p53-associated genes, a downstream transcriptional consequence distinct from the direct loss of histone acetylation. The specific disease-level consequences downstream of altered p53 signaling in KAT6A syndrome are not established, so this node is intentionally left as a terminal molecular readout.
signal transduction by p53 class mediator GO:0072331 ⚠ ABNORMAL
Show evidence (1 reference)
PMID:30245513 SUPPORT In Vitro
"demonstrated altered expression of p53- associated genes"
Patient fibroblast transcriptomics show altered p53-associated gene expression downstream of KAT6A dysfunction.
Altered Developmental Transcriptional Programs
Disrupted KAT6A-dependent histone acetylation alters the transcriptional programs that pattern the developing brain, craniofacial skeleton, heart, and other organs, producing the multisystem congenital and neurodevelopmental phenotype. The intervening steps from chromatin dysregulation to each organ-level endpoint are not individually resolved in humans.
regulation of transcription by RNA polymerase II GO:0006357 ⚠ ABNORMAL nervous system development GO:0007399 ⚠ ABNORMAL
Show evidence (1 reference)
PMID:30245513 SUPPORT Other
"These proteins form a complex to acetylate lysine residues on histone H3 tails, thereby promoting a wide range of developmental programs."
Supports the link between the KAT6A acetyltransferase complex and broad developmental transcriptional programs.
KAT6A-RSPO2-Wnt Hippocampal Signaling Deficit
In a mouse model, KAT6A deficiency lowers transcription of the CA3-enriched Wnt activator R-spondin 2 (RSPO2), impairing canonical Wnt signaling and synaptic structure and plasticity in hippocampal CA3 pyramidal neurons and producing memory deficits. Restoring RSPO2 in CA3 neurons rescues Wnt signaling and learning behaviors, nominating this axis as a candidate therapeutic target. This mechanism is currently established only in mice; its fidelity to human KAT6A-syndrome cognition is unproven.
hippocampal CA3 pyramidal neuron CL:1001571
canonical Wnt signaling pathway GO:0060070 ↓ DECREASED regulation of synaptic plasticity GO:0048167 ⚠ ABNORMAL learning or memory GO:0007611 ⚠ ABNORMAL
Show evidence (1 reference)
PMID:38758792 SUPPORT Model Organism
"Here, we find that KAT6A deficiency impairs synaptic structure and plasticity in hippocampal CA3, but not in CA1 region, resulting in memory deficits in mice."
The mouse model localizes the KAT6A cognitive mechanism to CA3 synaptic structure and plasticity.
Mitochondrial and Bioenergetic Dysfunction
Patient-derived fibroblasts carrying KAT6A mutations show impaired cellular bioenergetics alongside the histone-acetylation defect. This cellular bioenergetic deficit is the mechanistic rationale for the experimental pantothenate and L-carnitine intervention, which corrects it in vitro. The finding is from patient fibroblast models; its contribution to the clinical phenotype in vivo is not established.
Show evidence (1 reference)
PMID:36553567 SUPPORT In Vitro
"the cell bioenergetics of mutant cells was significantly improved"
That bioenergetics of mutant cells could be significantly improved by treatment establishes a baseline bioenergetic deficit in KAT6A-mutant fibroblasts.

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Arboleda-Tham Syndrome Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.

Phenotypes

27
Cardiovascular 4
Congenital Cardiac Defects FREQUENT Abnormal heart morphology HP:0001627
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Cardiac malformations are present in half (51%) of our cohort."
The cohort documents cardiac malformations in 51% of patients.
Atrial Septal Defect FREQUENT Atrial septal defect HP:0001631
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Most frequent are septal defects including atrial septal defects (34%), ventricular septal defects in (8%), and persistence of the fetal anatomy (19%) (patent foreman ovale, and persistent ductus arteriosus)."
The cohort reports atrial septal defects in 34% of patients, the most frequent cardiac lesion.
Ventricular Septal Defect OCCASIONAL Ventricular septal defect HP:0001629
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Most frequent are septal defects including atrial septal defects (34%), ventricular septal defects in (8%), and persistence of the fetal anatomy (19%) (patent foreman ovale, and persistent ductus arteriosus)."
The cohort reports ventricular septal defects in 8% of patients.
Patent Ductus Arteriosus OCCASIONAL Patent ductus arteriosus HP:0001643
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Most frequent are septal defects including atrial septal defects (34%), ventricular septal defects in (8%), and persistence of the fetal anatomy (19%) (patent foreman ovale, and persistent ductus arteriosus)."
Persistent ductus arteriosus is part of the persistence-of-fetal-anatomy category reported in 19% of the cohort (combined with patent foramen ovale).
Digestive 4
Feeding Difficulties FREQUENT Feeding difficulties HP:0011968
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"78% of patients experienced feeding difficulties."
The cohort reports feeding difficulties in 78% of patients, within the frequent band.
Constipation FREQUENT Constipation HP:0002019
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Constipation is a significant issue for over half of our patients and many are on long term laxatives."
The cohort documents constipation in over half of patients.
Gastroesophageal Reflux FREQUENT Gastroesophageal reflux HP:0002020
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"The high prevalence of reflux and constipation is suggestive of dysfunctional intestinal motility."
The cohort notes a high prevalence of reflux alongside constipation.
Intestinal Obstruction OCCASIONAL Intestinal obstruction HP:0005214
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"novel associations, including an increased risk of gastrointestinal obstruction."
The cohort identifies an increased risk of gastrointestinal obstruction as a novel association.
Ear 2
Low-Set, Posteriorly Rotated Ears OCCASIONAL Abnormal pinna morphology HP:0000377
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Notable features present in a significant minority are epicanthic folds and low set and posteriorly rotated ears, which are occasionally folded"
The cohort documents low-set, posteriorly rotated ears in a significant minority of patients.
Hearing Impairment Hearing impairment HP:0000365
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"These included microcephaly, neonatal hypotonia, feeding difficulties, reflux, constipation, congenital hearing defects, and frequent infections."
Congenital hearing defects are among the subphenotypes significantly more common in late-truncating variants; an overall cohort frequency is not given, so no frequency band is assigned.
Eye 1
Strabismus FREQUENT Strabismus HP:0000486
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Strabismus is reported in 54% of patients."
The cohort reports strabismus in 54% of patients.
Genitourinary 1
Cryptorchidism VERY_RARE Cryptorchidism HP:0000028
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"we found a small number of patients had undescended testes (boys), clinodactyly and/or brachydactyly."
The cohort documents undescended testes in a small number of male patients.
Head and Neck 5
Craniofacial Dysmorphism VERY_FREQUENT Abnormal facial shape HP:0001999
Show evidence (1 reference)
PMID:25728775 SUPPORT Human Clinical
"Common features among all four probands include primary microcephaly, global developmental delay including profound speech delay, and craniofacial dysmorphism"
The founding series lists craniofacial dysmorphism among the common features shared by all probands.
Broad Nasal Tip FREQUENT Broad nasal tip HP:0000455
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"A broad nasal tip, which may become more obvious with age, and a thin, tented upper lip, are the most consistent facial features in patients with KAT6A syndrome."
The cohort identifies broad nasal tip as one of the two most consistent facial features.
Microcephaly OCCASIONAL Microcephaly HP:0000252
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"in our larger cohort, only 25% individuals had microcephaly, which was not always present at birth."
The larger cohort reports microcephaly in 25% of patients, within the occasional band.
Craniosynostosis OCCASIONAL Craniosynostosis HP:0001363
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Craniosynostosis is reported in a total of 6 patients5."
The cohort reports craniosynostosis in a total of 6 patients.
Dental Anomalies FREQUENT Abnormality of the dentition HP:0000164
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"teeth abnormalities were common."
The cohort documents teeth abnormalities as common.
Immune 1
Recurrent Infections OCCASIONAL Recurrent infections HP:0002719
Show evidence (2 references)
PMID:30245513 SUPPORT Human Clinical
"those that did tended to report common childhood illnesses including otitis media and upper and lower respiratory tract infections"
The cohort documents recurrent common childhood infections in the subset of patients reporting frequent infections.
PMID:30245513 PARTIAL Human Clinical
"three individuals report isolated moderate to severe neutropenia5,13."
A minority have isolated neutropenia, a distinct immune finding that may contribute to infection susceptibility in some patients.
Musculoskeletal 1
Hypotonia FREQUENT Hypotonia HP:0001252
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Hypotonia is common and contributes to motor delay."
The cohort documents hypotonia as common and a contributor to motor delay.
Nervous System 5
Global Developmental Delay and Intellectual Disability OBLIGATE Intellectual disability HP:0001249
Show evidence (2 references)
PMID:30245513 SUPPORT Human Clinical
"Intellectual disability and developmental delay are universal."
The comprehensive cohort documents intellectual disability and developmental delay as universal.
PMID:38741077 SUPPORT Human Clinical
"Findings suggest global cognitive impairment with nonverbal cognition scores similar to those for receptive language"
A dedicated neuropsychological study characterizes the impairment as global, with nonverbal cognition tracking receptive language.
Expressive Speech Delay OBLIGATE Delayed speech and language development HP:0000750
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Marked expressive speech delay is universal."
The cohort documents marked expressive speech delay as universal.
Sleep Disturbance FREQUENT Sleep disturbance HP:0002360
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Over 30% of patients in this cohort reported sleep disturbance."
The cohort reports sleep disturbance in over 30% of patients.
Autistic Behavior OCCASIONAL Autistic behavior HP:0000729
Show evidence (2 references)
PMID:30245513 SUPPORT Human Clinical
"Autism and autistic features have been reported in approximately 25% of newly reported cases."
The cohort reports autism/autistic features in approximately 25% of newly reported cases.
PMID:38741077 SUPPORT Human Clinical
"Autism-related features, particularly restricted interests and repetitive behaviors, and broad adaptive deficits were common in our sample juxtaposed with a relatively strong social drive and low frequency of internalizing and externalizing behavioral problems."
A dedicated neuropsychological study characterizes the autism-related features and their relative sparing of social drive.
Seizures OCCASIONAL Seizure HP:0001250
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Seizure activity has only been reported in seven patients and there is no consistency in seizure type"
The cohort reports seizures in only seven patients, an uncommon feature.
Other 3
Thin, Tented Upper Lip FREQUENT Thin upper lip vermilion HP:0000219
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"A broad nasal tip, which may become more obvious with age, and a thin, tented upper lip, are the most consistent facial features in patients with KAT6A syndrome."
The cohort identifies a thin, tented upper lip as one of the two most consistent facial features.
Patent Foramen Ovale OCCASIONAL Patent foramen ovale HP:0001655
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Most frequent are septal defects including atrial septal defects (34%), ventricular septal defects in (8%), and persistence of the fetal anatomy (19%) (patent foreman ovale, and persistent ductus arteriosus)."
Patent foramen ovale is part of the persistence-of-fetal-anatomy category reported in 19% of the cohort (combined with patent ductus arteriosus).
Amblyopia VERY_RARE Amblyopia HP:0000646
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Amblyopia is reported in several patients."
The cohort documents amblyopia in several patients, an uncommon secondary complication of strabismus.
🧬

Genetic Associations

1
KAT6A Pathogenic Variants (Causative)
Gene: KAT6A hgnc:13013 relationship_type: CAUSATIVE variant_origin: GERMLINE
Autosomal dominant inheritance
Show evidence (2 references)
PMID:25728777 SUPPORT Human Clinical
"Finally, by detailed clinical characterization we provide evidence that heterozygous mutations in KAT6A cause a distinct intellectual disability syndrome."
Establishes KAT6A as the causative gene for a distinct intellectual disability syndrome.
PMID:30245513 SUPPORT Human Clinical
"Our analysis identifies hotspot nonsense mutations within the penultimate exons at amino acid positions 1019, 1024, and 1129 that account for 19.1% (13/68) of pathogenic variants in unrelated individuals."
Quantifies the recurrent truncating hotspots that make up a substantial fraction of pathogenic variants.
💊

Medical Actions

4
Multidisciplinary Supportive Care
Category: Therapeutic Action: supportive care Ontology label: Supportive Care NCIT:C15747
Management is symptomatic and individualized, coordinating developmental, nutritional, gastrointestinal, cardiac, ophthalmologic, and infectious-disease care. Early cardiology assessment with echocardiography is recommended given the high prevalence of cardiac lesions.
Target Phenotypes: Abnormal heart morphology HP:0001627
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"The prevalence of cardiac lesions highlights the need for early cardiology assessment."
The cohort recommends early cardiology assessment as part of individualized multidisciplinary care.
Speech and Language Therapy
Category: Therapeutic Action: speech therapy Ontology label: Speech Language Therapy NCIT:C159273
Speech and language therapy, augmented by sign language and communication aids, addresses the universal expressive speech delay and verbal dyspraxia.
Target Phenotypes: Delayed speech and language development HP:0000750
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"Use of sign language and communication aids are helpful."
The cohort supports communication-focused intervention for the characteristic expressive speech delay.
Cardiac Surgical or Catheter Intervention
Category: Therapeutic Action: septal defect repair Ontology label: Septal Defect Repair NCIT:C148075
A substantial proportion of patients with cardiac malformations require intervention by open-heart surgery or cardiac catheterization.
Target Phenotypes: Atrial septal defect HP:0001631
Show evidence (1 reference)
PMID:30245513 SUPPORT Human Clinical
"At least 45% of patients with cardiac malformations required intervention (open heart surgery or via cardiac catheterization)."
The cohort documents cardiac intervention in at least 45% of patients with cardiac malformations.
Pantothenate and L-Carnitine Supplementation
Category: Therapeutic Action: nutritional supplementation Ontology label: Nutritional Support NCIT:C15433
Agent: pantothenate CHEBI:16454 L-carnitine CHEBI:16347
An experimental, preclinical intervention. In patient-derived fibroblast models of KAT6A syndrome, pantothenate plus L-carnitine increased histone acetylation, partially corrected protein and transcriptomic expression patterns, and improved cell bioenergetics. This is in vitro evidence only and has not been evaluated as a clinical therapy.
Mechanism Target:
RESTORES Mitochondrial and Bioenergetic Dysfunction — Pantothenate (a CoA precursor) and L-carnitine act as mitochondrial boosting agents that improve the impaired cell bioenergetics of KAT6A-mutant fibroblasts in vitro; this is the mechanistic rationale for the intervention.
Show evidence (1 reference)
PMID:36553567 SUPPORT In Vitro
"Pantothenate and L-carnitine treatment increased histone acetylation and partially corrected protein and transcriptomic expression patterns in mutant KAT6A cells."
Patient-derived fibroblast models show that pantothenate and L-carnitine partially correct KAT6A-associated cellular abnormalities, an experimental preclinical lead.
{ }

Source YAML

click to show
name: Arboleda-Tham Syndrome
creation_date: "2026-07-30T00:00:00Z"
synonyms:
- KAT6A syndrome
- KAT6A-related intellectual disability
- Mental retardation, autosomal dominant 32
- MRD32
description: >-
  Arboleda-Tham syndrome (KAT6A syndrome) is an autosomal dominant
  neurodevelopmental disorder caused by heterozygous, usually de novo,
  pathogenic variants in KAT6A, a MYST-family lysine acetyltransferase that
  acetylates histone H3 (notably H3K9 and H3K18) within a multi-subunit complex
  with BRPF1/2/3, ING5, and hEAF6 to drive developmental transcriptional
  programs. The core phenotype comprises global developmental delay with
  near-universal intellectual disability and marked expressive speech delay,
  neonatal hypotonia, early feeding and oromotor difficulties, recognizable
  craniofacial dysmorphism (broad nasal tip and thin, tented upper lip), and
  congenital cardiac defects, most often septal defects. Gastrointestinal
  dysmotility (reflux, constipation, and an increased risk of intestinal
  obstruction), microcephaly, ophthalmologic anomalies (notably strabismus),
  recurrent infections, and variable behavioral features complete the spectrum.
  A genotype-phenotype correlation is recognized: early-truncating variants
  (exons 1-15) are predicted to trigger nonsense-mediated decay and
  haploinsufficiency and are associated with milder disease, whereas
  late-truncating variants (exons 16-17) escape nonsense-mediated decay and are
  associated with more severe developmental delay and a higher frequency of
  several syndromic features.
category: Mendelian
disease_term:
  preferred_term: KAT6A syndrome
  term:
    id: MONDO:0014558
    label: autosomal dominant intellectual disability-craniofacial anomalies-cardiac defects syndrome
parents:
- autosomal dominant syndromic intellectual disability
- multiple congenital anomalies/dysmorphic syndrome-intellectual disability

inheritance:
- name: Autosomal dominant inheritance
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Arboleda-Tham syndrome is autosomal dominant and is almost always caused by
    a de novo heterozygous pathogenic KAT6A variant.
  evidence:
  - reference: PMID:25728775
    reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here, we report a syndrome caused by de novo heterozygous nonsense
      mutations in KAT6A (a.k.a., MOZ, MYST3) identified by clinical exome
      sequencing (CES) in four independent families.
    explanation: >-
      The founding series establishes heterozygous, de novo KAT6A variants as
      the cause, consistent with autosomal dominant inheritance.
  penetrance: COMPLETE
  expressivity: VARIABLE

references:
- reference: PMID:25728775
  title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
- reference: PMID:25728777
  title: "Dominant mutations in KAT6A cause intellectual disability with recognizable syndromic features."
- reference: PMID:30245513
  title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
- reference: PMID:38741077
  title: "Neuropsychological profile associated with KAT6A syndrome: Emergent genotype-phenotype trends."
- reference: PMID:38758792
  title: "KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3."
- reference: PMID:36553567
  title: "Pantothenate and L-Carnitine Supplementation Improves Pathological Alterations in Cellular Models of KAT6A Syndrome."

mechanistic_hypotheses:
- hypothesis_group_id: early_truncating_nmd_haploinsufficiency
  hypothesis_label: Early-Truncating NMD / Haploinsufficiency Branch
  status: CANONICAL
  description: >-
    Truncating variants in exons 1-15 are predicted to trigger
    nonsense-mediated decay of the mutant transcript, producing KAT6A
    haploinsufficiency. This branch is associated with a milder phenotype, with
    a majority of early-truncating cases rated as having mild intellectual
    disability.
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This suggests a potential role for nonsense mediated decay (NMD), where
      truncating mutations in the first 15 exons trigger NMD mechanisms and
      result in haploinsufficiency while mutations in exons 16 and 17 would not
      result in NMD, therefore the mRNA would result in a translated but
      dysfunctional protein that may have gain-of function or dominant negative
      effects.
    explanation: >-
      The genotype-phenotype study proposes NMD-mediated haploinsufficiency for
      early-truncating variants as the basis for milder disease.
- hypothesis_group_id: late_truncating_nmd_escape
  hypothesis_label: Late-Truncating NMD-Escape Branch
  status: ALTERNATIVE
  description: >-
    Truncating variants in the last two exons (16-17) escape nonsense-mediated
    decay and are predicted to yield a translated but dysfunctional protein with
    possible gain-of-function or dominant-negative effects. This branch is
    associated with more severe developmental delay and a higher frequency of
    several syndromic features. Direct demonstration of mutant protein and its
    mode of action in patient tissue remains an evidence gap.
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      95% of late truncating cases (exon 16 and 17) were rated as moderate or
      severe, while 60% of early truncating cases (exons 1-15) were rated as
      mild
    explanation: >-
      The cohort documents the more severe developmental phenotype associated
      with the NMD-escaping late-truncating branch.
- hypothesis_group_id: kat6a_rspo2_wnt_hippocampal
  hypothesis_label: KAT6A-RSPO2-Wnt Hippocampal Signaling Branch
  status: EMERGING
  description: >-
    An emerging mechanism, so far demonstrated only in mice, links KAT6A
    deficiency to impaired cognition through a specific transcriptional target:
    KAT6A activates the CA3-enriched Wnt activator R-spondin 2 (RSPO2), and its
    loss reduces hippocampal CA3 synaptic structure, plasticity, and Wnt
    signaling. Restoring RSPO2 in CA3 neurons rescues Wnt signaling and
    learning behaviors in Kat6a mutant mice, nominating the KAT6A-RSPO2-Wnt axis
    as a candidate therapeutic target. Fidelity to human KAT6A-syndrome
    cognition is not yet established.
  evidence:
  - reference: PMID:38758792
    reference_title: "KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Collectively, our results demonstrate that KAT6A-RSPO2-Wnt signaling plays
      a critical role in regulating hippocampal CA3 synaptic plasticity and
      cognitive function, providing potential therapeutic targets for KAT6A
      syndrome and related neurodevelopmental diseases.
    explanation: >-
      A mouse study defines the KAT6A-RSPO2-Wnt hippocampal axis as an emerging
      mechanism of the cognitive phenotype and a candidate therapeutic target.

pathophysiology:
- name: Heterozygous KAT6A Pathogenic Variation
  description: >-
    The initiating lesion is a heterozygous, usually de novo, pathogenic KAT6A
    variant. Most established alleles are protein-truncating (nonsense or
    frameshift), with recurrent hotspots in the arginine-rich acidic domain, and
    are distributed across the gene with a bias toward the last two exons.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  genes:
  - preferred_term: KAT6A
    term:
      id: hgnc:13013
      label: KAT6A
  evidence:
  - reference: PMID:25728777
    reference_title: "Dominant mutations in KAT6A cause intellectual disability with recognizable syndromic features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All five different de novo heterozygous truncating mutations were located
      in the C-terminal transactivation domain of KAT6A
    explanation: >-
      The founding series establishes heterozygous, de novo truncating KAT6A
      variants clustered in the C-terminal domain.
  downstream:
  - target: Mitochondrial and Bioenergetic Dysfunction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:36553567
      reference_title: "Pantothenate and L-Carnitine Supplementation Improves Pathological Alterations in Cellular Models of KAT6A Syndrome."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        we examined the pathophysiological alterations in fibroblasts derived
        from three patients harboring KAT6A mutations
      explanation: >-
        Patient fibroblasts harboring KAT6A mutations exhibit the
        pathophysiological alterations, including the bioenergetic deficit; the
        intervening steps are unresolved.
  - target: NMD-Mediated KAT6A Haploinsufficiency
    causal_link_type: DIRECT
    hypothesis_groups:
    - early_truncating_nmd_haploinsufficiency
    evidence:
    - reference: PMID:30245513
      reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        This suggests a potential role for nonsense mediated decay (NMD), where
        truncating mutations in the first 15 exons trigger NMD mechanisms and
        result in haploinsufficiency while mutations in exons 16 and 17 would not
        result in NMD, therefore the mRNA would result in a translated but
        dysfunctional protein that may have gain-of function or dominant negative
        effects.
      explanation: >-
        For early-truncating (exon 1-15) variants, NMD of the mutant transcript
        is proposed to produce KAT6A haploinsufficiency.
  - target: NMD-Escaping Dysfunctional KAT6A Protein
    causal_link_type: DIRECT
    hypothesis_groups:
    - late_truncating_nmd_escape
    evidence:
    - reference: PMID:30245513
      reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        This suggests a potential role for nonsense mediated decay (NMD), where
        truncating mutations in the first 15 exons trigger NMD mechanisms and
        result in haploinsufficiency while mutations in exons 16 and 17 would not
        result in NMD, therefore the mRNA would result in a translated but
        dysfunctional protein that may have gain-of function or dominant negative
        effects.
      explanation: >-
        For late-truncating (exon 16-17) variants, escape from NMD is proposed to
        yield a translated but dysfunctional protein with possible
        gain-of-function or dominant-negative activity.

- name: NMD-Mediated KAT6A Haploinsufficiency
  description: >-
    Early-truncating variants (exons 1-15) are predicted to trigger
    nonsense-mediated decay of the mutant transcript, reducing functional KAT6A
    dosage (haploinsufficiency). This is the canonical route and is associated
    with milder disease.
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  downstream:
  - target: Dysregulated Histone H3 Acetylation
    causal_link_type: DIRECT
    hypothesis_groups:
    - early_truncating_nmd_haploinsufficiency
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        We further demonstrate that KAT6A mutations result in dysregulation of
        H3K9 and H3K18 acetylation and altered P53 signaling.
      explanation: >-
        Reduced KAT6A dosage converges on dysregulated histone H3 acetylation.

- name: NMD-Escaping Dysfunctional KAT6A Protein
  description: >-
    Late-truncating variants (exons 16-17) escape nonsense-mediated decay and
    are predicted to produce a translated but dysfunctional protein that may act
    by gain-of-function or dominant-negative mechanisms. This is the alternative
    route and is associated with more severe disease. Direct demonstration of
    mutant protein and its mode of action in patient tissue remains an evidence
    gap.
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  downstream:
  - target: Dysregulated Histone H3 Acetylation
    causal_link_type: DIRECT
    hypothesis_groups:
    - late_truncating_nmd_escape
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        We further demonstrate that KAT6A mutations result in dysregulation of
        H3K9 and H3K18 acetylation and altered P53 signaling.
      explanation: >-
        A dysfunctional protein likewise converges on dysregulated histone H3
        acetylation.

- name: Dysregulated Histone H3 Acetylation
  description: >-
    KAT6A (MOZ/MYST3) is a MYST-family histone acetyltransferase that, within a
    complex containing BRPF1/2/3, ING5, and hEAF6, acetylates lysine residues on
    histone H3 tails (notably H3K9 and H3K18). Pathogenic variants dysregulate
    H3K9 and H3K18 acetylation, altering the chromatin state that governs
    developmental gene expression. (GO lacks a current, non-obsolete
    histone-H3-specific acetylation biological-process term; the H3 specificity
    is carried by the H3K9 and H3K18 molecular-function annotations.)
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  molecular_functions:
  - preferred_term: histone acetyltransferase activity
    term:
      id: GO:0004402
      label: histone acetyltransferase activity
  - preferred_term: histone H3K9 acetyltransferase activity
    term:
      id: GO:0043992
      label: histone H3K9 acetyltransferase activity
    modifier: DYSREGULATED
  - preferred_term: histone H3K18 acetyltransferase activity
    term:
      id: GO:0043993
      label: histone H3K18 acetyltransferase activity
    modifier: DYSREGULATED
  biological_processes:
  - preferred_term: chromatin organization
    term:
      id: GO:0006325
      label: chromatin organization
    modifier: ABNORMAL
  evidence:
  - reference: PMID:25728775
    reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We further demonstrate that KAT6A mutations result in dysregulation of
      H3K9 and H3K18 acetylation and altered P53 signaling.
    explanation: >-
      Directly supports dysregulated H3K9/H3K18 acetylation as the molecular
      consequence of KAT6A mutation.
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      KAT6A and KAT6B each function in a multi-subunit complex with three other
      proteins: BRPF1/2/3, ING5 and hEAF6
    explanation: >-
      Establishes the KAT6A histone-acetyltransferase complex through which the
      enzyme acts on histone H3.
  downstream:
  - target: Altered p53 Signaling
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        We further demonstrate that KAT6A mutations result in dysregulation of
        H3K9 and H3K18 acetylation and altered P53 signaling.
      explanation: >-
        Dysregulated acetylation is accompanied by altered p53 signaling in the
        same functional study.
  - target: Altered Developmental Transcriptional Programs
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30245513
      reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        These proteins form a complex to acetylate lysine residues on histone H3
        tails, thereby promoting a wide range of developmental programs.
      explanation: >-
        Links KAT6A-mediated histone H3 acetylation to the developmental
        transcriptional programs disrupted in the disorder.

- name: Altered p53 Signaling
  description: >-
    Beyond its direct catalytic effect on histone H3, KAT6A dysfunction perturbs
    p53-associated transcriptional programs. Patient-derived fibroblasts show
    altered expression of p53-associated genes, a downstream transcriptional
    consequence distinct from the direct loss of histone acetylation. The
    specific disease-level consequences downstream of altered p53 signaling in
    KAT6A syndrome are not established, so this node is intentionally left as a
    terminal molecular readout.
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  biological_processes:
  - preferred_term: signal transduction by p53 class mediator
    term:
      id: GO:0072331
      label: signal transduction by p53 class mediator
    modifier: ABNORMAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      demonstrated altered expression of p53- associated genes
    explanation: >-
      Patient fibroblast transcriptomics show altered p53-associated gene
      expression downstream of KAT6A dysfunction.

- name: Altered Developmental Transcriptional Programs
  description: >-
    Disrupted KAT6A-dependent histone acetylation alters the transcriptional
    programs that pattern the developing brain, craniofacial skeleton, heart, and
    other organs, producing the multisystem congenital and neurodevelopmental
    phenotype. The intervening steps from chromatin dysregulation to each
    organ-level endpoint are not individually resolved in humans.
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  biological_processes:
  - preferred_term: regulation of transcription by RNA polymerase II
    term:
      id: GO:0006357
      label: regulation of transcription by RNA polymerase II
    modifier: ABNORMAL
  - preferred_term: nervous system development
    term:
      id: GO:0007399
      label: nervous system development
    modifier: ABNORMAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      These proteins form a complex to acetylate lysine residues on histone H3
      tails, thereby promoting a wide range of developmental programs.
    explanation: >-
      Supports the link between the KAT6A acetyltransferase complex and broad
      developmental transcriptional programs.
  downstream:
  - target: Global Developmental Delay and Intellectual Disability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Common features among all four probands include primary microcephaly,
        global developmental delay including profound speech delay, and
        craniofacial dysmorphism, as well as more varied features such as
        feeding difficulties, cardiac defects, and ocular anomalies.
      explanation: >-
        Links KAT6A dysfunction to the core neurodevelopmental phenotype.
  - target: Expressive Speech Delay
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Common features among all four probands include primary microcephaly,
        global developmental delay including profound speech delay, and
        craniofacial dysmorphism
      explanation: >-
        Profound speech delay is part of the core developmental phenotype; the
        intervening mechanism is unresolved.
  - target: Craniofacial Dysmorphism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Common features among all four probands include primary microcephaly,
        global developmental delay including profound speech delay, and
        craniofacial dysmorphism
      explanation: >-
        Links KAT6A dysfunction to craniofacial dysmorphism.
  - target: Congenital Cardiac Defects
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        more varied features such as feeding difficulties, cardiac defects, and
        ocular anomalies.
      explanation: >-
        Links KAT6A dysfunction to congenital cardiac defects among the varied
        multisystem features.
  - target: Hypotonia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25728777
      reference_title: "Dominant mutations in KAT6A cause intellectual disability with recognizable syndromic features."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The common phenotype includes hypotonia, intellectual disability, early
        feeding and oromotor difficulties, microcephaly and/or craniosynostosis,
        and cardiac defects in combination with subtle facial features such as
        bitemporal narrowing, broad nasal tip, thin upper lip
      explanation: >-
        The common phenotype includes hypotonia; the intervening developmental
        mechanism is unresolved.
  - target: Feeding Difficulties
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25728777
      reference_title: "Dominant mutations in KAT6A cause intellectual disability with recognizable syndromic features."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The common phenotype includes hypotonia, intellectual disability, early
        feeding and oromotor difficulties, microcephaly and/or craniosynostosis,
        and cardiac defects in combination with subtle facial features such as
        bitemporal narrowing, broad nasal tip, thin upper lip
      explanation: >-
        Early feeding and oromotor difficulties are part of the common
        developmental phenotype.
  - target: Microcephaly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Common features among all four probands include primary microcephaly,
        global developmental delay including profound speech delay, and
        craniofacial dysmorphism
      explanation: >-
        Primary microcephaly is a common feature of the disorder; the
        developmental bridge is unresolved.
  - target: Gastroesophageal Reflux
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30245513
      reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The high prevalence of reflux and constipation is suggestive of
        dysfunctional intestinal motility.
      explanation: >-
        Reflux is linked to dysfunctional intestinal motility, plausibly a
        developmental consequence of KAT6A dysfunction.
  - target: Constipation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30245513
      reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The high prevalence of reflux and constipation is suggestive of
        dysfunctional intestinal motility.
      explanation: >-
        Constipation is linked to dysfunctional intestinal motility, plausibly a
        developmental consequence of KAT6A dysfunction.
  - target: KAT6A-RSPO2-Wnt Hippocampal Signaling Deficit
    causal_link_type: DIRECT
    hypothesis_groups:
    - kat6a_rspo2_wnt_hippocampal
    evidence:
    - reference: PMID:38758792
      reference_title: "KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We further identify a CA3-enriched gene Rspo2, encoding Wnt activator
        R-spondin 2, as a key transcriptional target of KAT6A.
      explanation: >-
        In mice, RSPO2 is a direct transcriptional target of KAT6A, linking the
        acetyltransferase to a specific hippocampal signaling program.

- name: KAT6A-RSPO2-Wnt Hippocampal Signaling Deficit
  description: >-
    In a mouse model, KAT6A deficiency lowers transcription of the CA3-enriched
    Wnt activator R-spondin 2 (RSPO2), impairing canonical Wnt signaling and
    synaptic structure and plasticity in hippocampal CA3 pyramidal neurons and
    producing memory deficits. Restoring RSPO2 in CA3 neurons rescues Wnt
    signaling and learning behaviors, nominating this axis as a candidate
    therapeutic target. This mechanism is currently established only in mice; its
    fidelity to human KAT6A-syndrome cognition is unproven.
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  cell_types:
  - preferred_term: hippocampal CA3 pyramidal neuron
    term:
      id: CL:1001571
      label: hippocampal pyramidal neuron
  biological_processes:
  - preferred_term: canonical Wnt signaling pathway
    term:
      id: GO:0060070
      label: canonical Wnt signaling pathway
    modifier: DECREASED
  - preferred_term: regulation of synaptic plasticity
    term:
      id: GO:0048167
      label: regulation of synaptic plasticity
    modifier: ABNORMAL
  - preferred_term: learning or memory
    term:
      id: GO:0007611
      label: learning or memory
    modifier: ABNORMAL
  evidence:
  - reference: PMID:38758792
    reference_title: "KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Here, we find that KAT6A deficiency impairs synaptic structure and
      plasticity in hippocampal CA3, but not in CA1 region, resulting in memory
      deficits in mice.
    explanation: >-
      The mouse model localizes the KAT6A cognitive mechanism to CA3 synaptic
      structure and plasticity.
  downstream:
  - target: Global Developmental Delay and Intellectual Disability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - kat6a_rspo2_wnt_hippocampal
    evidence:
    - reference: PMID:38758792
      reference_title: "KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3."
      supports: PARTIAL
      evidence_source: MODEL_ORGANISM
      snippet: >-
        restoring RSPO2 expression in CA3 neurons rescues the deficits in Wnt
        signaling and learning-associated behaviors in Kat6a mutant mice.
      explanation: >-
        Rescue of learning behaviors in mice links the RSPO2-Wnt deficit to the
        cognitive phenotype, though human relevance is not yet established.

- name: Mitochondrial and Bioenergetic Dysfunction
  description: >-
    Patient-derived fibroblasts carrying KAT6A mutations show impaired cellular
    bioenergetics alongside the histone-acetylation defect. This cellular
    bioenergetic deficit is the mechanistic rationale for the experimental
    pantothenate and L-carnitine intervention, which corrects it in vitro. The
    finding is from patient fibroblast models; its contribution to the clinical
    phenotype in vivo is not established.
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:36553567
    reference_title: "Pantothenate and L-Carnitine Supplementation Improves Pathological Alterations in Cellular Models of KAT6A Syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "the cell bioenergetics of mutant cells was significantly improved"
    explanation: >-
      That bioenergetics of mutant cells could be significantly improved by
      treatment establishes a baseline bioenergetic deficit in KAT6A-mutant
      fibroblasts.

phenotypes:
- category: Neurologic
  name: Global Developmental Delay and Intellectual Disability
  description: >-
    Global developmental delay and intellectual disability are universal,
    ranging from mild to severe. Level of intellectual disability correlates
    with variant position, being more severe in late-truncating variants.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  frequency: OBLIGATE
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intellectual disability and developmental delay are universal."
    explanation: >-
      The comprehensive cohort documents intellectual disability and
      developmental delay as universal.
  - reference: PMID:38741077
    reference_title: "Neuropsychological profile associated with KAT6A syndrome: Emergent genotype-phenotype trends."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Findings suggest global cognitive impairment with nonverbal cognition
      scores similar to those for receptive language
    explanation: >-
      A dedicated neuropsychological study characterizes the impairment as
      global, with nonverbal cognition tracking receptive language.
- category: Neurodevelopmental
  name: Expressive Speech Delay
  description: >-
    Marked expressive speech delay is universal and often described as a form of
    verbal dyspraxia, with receptive language consistently more developed than
    expressive language.
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  frequency: OBLIGATE
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Marked expressive speech delay is universal."
    explanation: >-
      The cohort documents marked expressive speech delay as universal.
- category: Neurologic
  name: Hypotonia
  description: >-
    Hypotonia is common, frequently with neonatal onset, and contributes to
    motor delay; truncal hypotonia is often combined with limb hypertonia in the
    neonatal period. Neonatal hypotonia is one of the features significantly
    more common in late-truncating variants.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypotonia is common and contributes to motor delay."
    explanation: >-
      The cohort documents hypotonia as common and a contributor to motor delay.
- category: Gastrointestinal
  name: Feeding Difficulties
  description: >-
    Feeding difficulties are common, frequently with oromotor dysfunction and
    difficulty establishing feeding at birth; nasogastric feeding is often
    required and some patients need gastrostomy.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "78% of patients experienced feeding difficulties."
    explanation: >-
      The cohort reports feeding difficulties in 78% of patients, within the
      frequent band.
- category: Cardiovascular
  name: Congenital Cardiac Defects
  description: >-
    Cardiac malformations, most often septal defects, are present in about half
    of patients; atrial septal defects are the most frequent, followed by
    ventricular septal defects and persistence of fetal anatomy (patent foramen
    ovale, patent ductus arteriosus). Many require intervention.
  phenotype_term:
    preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cardiac malformations are present in half (51%) of our cohort."
    explanation: >-
      The cohort documents cardiac malformations in 51% of patients.
- category: Cardiovascular
  name: Atrial Septal Defect
  description: >-
    Atrial septal defect is the most frequent cardiac lesion in KAT6A syndrome.
  phenotype_term:
    preferred_term: Atrial septal defect
    term:
      id: HP:0001631
      label: Atrial septal defect
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most frequent are septal defects including atrial septal defects (34%),
      ventricular septal defects in (8%), and persistence of the fetal anatomy
      (19%) (patent foreman ovale, and persistent ductus arteriosus).
    explanation: >-
      The cohort reports atrial septal defects in 34% of patients, the most
      frequent cardiac lesion.
- category: Cardiovascular
  name: Ventricular Septal Defect
  description: >-
    Ventricular septal defect occurs in a minority of patients with cardiac
    involvement.
  phenotype_term:
    preferred_term: Ventricular septal defect
    term:
      id: HP:0001629
      label: Ventricular septal defect
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most frequent are septal defects including atrial septal defects (34%),
      ventricular septal defects in (8%), and persistence of the fetal anatomy
      (19%) (patent foreman ovale, and persistent ductus arteriosus).
    explanation: >-
      The cohort reports ventricular septal defects in 8% of patients.
- category: Craniofacial
  name: Craniofacial Dysmorphism
  description: >-
    Recognizable craniofacial dysmorphism is a core feature, most consistently a
    broad nasal tip and a thin, tented upper lip, with additional features
    including bitemporal narrowing, prominent nasal bridge, and a short, flat
    philtrum.
  phenotype_term:
    preferred_term: Craniofacial dysmorphism
    term:
      id: HP:0001999
      label: Abnormal facial shape
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:25728775
    reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common features among all four probands include primary microcephaly,
      global developmental delay including profound speech delay, and
      craniofacial dysmorphism
    explanation: >-
      The founding series lists craniofacial dysmorphism among the common
      features shared by all probands.
- category: Craniofacial
  name: Broad Nasal Tip
  description: >-
    A broad nasal tip, which may become more obvious with age, is one of the two
    most consistent facial features of KAT6A syndrome.
  phenotype_term:
    preferred_term: Broad nasal tip
    term:
      id: HP:0000455
      label: Broad nasal tip
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A broad nasal tip, which may become more obvious with age, and a thin,
      tented upper lip, are the most consistent facial features in patients with
      KAT6A syndrome.
    explanation: >-
      The cohort identifies broad nasal tip as one of the two most consistent
      facial features.
- category: Craniofacial
  name: Thin, Tented Upper Lip
  description: >-
    A thin, tented upper lip is one of the two most consistent facial features
    of KAT6A syndrome.
  phenotype_term:
    preferred_term: Thin, tented upper lip vermilion
    term:
      id: HP:0000219
      label: Thin upper lip vermilion
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A broad nasal tip, which may become more obvious with age, and a thin,
      tented upper lip, are the most consistent facial features in patients with
      KAT6A syndrome.
    explanation: >-
      The cohort identifies a thin, tented upper lip as one of the two most
      consistent facial features.
- category: Neurologic
  name: Microcephaly
  description: >-
    Microcephaly is present in roughly a quarter of patients and is not always
    present at birth; earlier smaller series reported a higher rate.
    Microcephaly is one of the features significantly more common in
    late-truncating variants.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      in our larger cohort, only 25% individuals had microcephaly, which was not
      always present at birth.
    explanation: >-
      The larger cohort reports microcephaly in 25% of patients, within the
      occasional band.
- category: Ophthalmologic
  name: Strabismus
  description: >-
    Strabismus is a common ophthalmologic finding, can be intermittent, and may
    lead to amblyopia if unrecognized and untreated.
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Strabismus is reported in 54% of patients."
    explanation: >-
      The cohort reports strabismus in 54% of patients.
- category: Gastrointestinal
  name: Constipation
  description: >-
    Constipation affects over half of patients, many requiring long-term
    laxatives, and is one of the features significantly more common in
    late-truncating variants.
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Constipation is a significant issue for over half of our patients and many
      are on long term laxatives.
    explanation: >-
      The cohort documents constipation in over half of patients.
- category: Gastrointestinal
  name: Gastroesophageal Reflux
  description: >-
    Gastroesophageal reflux is a significant and prevalent issue, suggestive of
    dysfunctional intestinal motility, and some patients require fundoplication.
  phenotype_term:
    preferred_term: Gastroesophageal reflux
    term:
      id: HP:0002020
      label: Gastroesophageal reflux
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The high prevalence of reflux and constipation is suggestive of
      dysfunctional intestinal motility.
    explanation: >-
      The cohort notes a high prevalence of reflux alongside constipation.
- category: Gastrointestinal
  name: Intestinal Obstruction
  description: >-
    An increased risk of gastrointestinal obstruction is a novel association;
    several patients had bowel obstruction, in some cases from malrotation or a
    duodenal web, requiring surgery.
  phenotype_term:
    preferred_term: Intestinal obstruction
    term:
      id: HP:0005214
      label: Intestinal obstruction
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "novel associations, including an increased risk of gastrointestinal obstruction."
    explanation: >-
      The cohort identifies an increased risk of gastrointestinal obstruction as
      a novel association.
- category: Neurologic
  name: Sleep Disturbance
  description: >-
    Over 30% of patients report sleep disturbance, including difficulty
    initiating and maintaining sleep, and some have central or obstructive sleep
    apnea.
  phenotype_term:
    preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over 30% of patients in this cohort reported sleep disturbance."
    explanation: >-
      The cohort reports sleep disturbance in over 30% of patients.
- category: Psychiatric
  name: Autistic Behavior
  description: >-
    Autism and autistic features, particularly restricted interests and
    repetitive behaviors, are reported in roughly a quarter of newly reported
    cases, often juxtaposed with a relatively strong social drive.
  phenotype_term:
    preferred_term: Autistic behavior
    term:
      id: HP:0000729
      label: Autistic behavior
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Autism and autistic features have been reported in approximately 25% of
      newly reported cases.
    explanation: >-
      The cohort reports autism/autistic features in approximately 25% of newly
      reported cases.
  - reference: PMID:38741077
    reference_title: "Neuropsychological profile associated with KAT6A syndrome: Emergent genotype-phenotype trends."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Autism-related features, particularly restricted interests and repetitive
      behaviors, and broad adaptive deficits were common in our sample
      juxtaposed with a relatively strong social drive and low frequency of
      internalizing and externalizing behavioral problems.
    explanation: >-
      A dedicated neuropsychological study characterizes the autism-related
      features and their relative sparing of social drive.
- category: Immunologic
  name: Recurrent Infections
  description: >-
    Frequent infections are reported in a subset of patients, most commonly
    common childhood illnesses (otitis media, respiratory tract infections);
    frequent infections are significantly more common in late-truncating
    variants. A minority have isolated neutropenia or other immune findings.
  phenotype_term:
    preferred_term: Recurrent infections
    term:
      id: HP:0002719
      label: Recurrent infections
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those that did tended to report common childhood illnesses including
      otitis media and upper and lower respiratory tract infections
    explanation: >-
      The cohort documents recurrent common childhood infections in the subset
      of patients reporting frequent infections.
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "three individuals report isolated moderate to severe neutropenia5,13."
    explanation: >-
      A minority have isolated neutropenia, a distinct immune finding that may
      contribute to infection susceptibility in some patients.
- category: Neurologic
  name: Seizures
  description: >-
    Seizures are uncommon and reported in only a few patients, with no
    consistent seizure type.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Seizure activity has only been reported in seven patients and there is no
      consistency in seizure type
    explanation: >-
      The cohort reports seizures in only seven patients, an uncommon feature.
- category: Craniofacial
  name: Craniosynostosis
  description: >-
    Craniosynostosis is an uncommon feature, reported in a small number of
    patients.
  phenotype_term:
    preferred_term: Craniosynostosis
    term:
      id: HP:0001363
      label: Craniosynostosis
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Craniosynostosis is reported in a total of 6 patients5."
    explanation: >-
      The cohort reports craniosynostosis in a total of 6 patients.
- category: Craniofacial
  name: Low-Set, Posteriorly Rotated Ears
  description: >-
    Low-set and posteriorly rotated ears, occasionally folded, are present in a
    significant minority, alongside epicanthic folds.
  phenotype_term:
    preferred_term: Low-set, posteriorly rotated ears
    term:
      id: HP:0000377
      label: Abnormal pinna morphology
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Notable features present in a significant minority are epicanthic folds
      and low set and posteriorly rotated ears, which are occasionally folded
    explanation: >-
      The cohort documents low-set, posteriorly rotated ears in a significant
      minority of patients.
- category: Otologic
  name: Hearing Impairment
  description: >-
    Congenital hearing defects occur in KAT6A syndrome and are one of the
    features significantly enriched in patients with late-truncating variants.
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These included microcephaly, neonatal hypotonia, feeding difficulties,
      reflux, constipation, congenital hearing defects, and frequent infections.
    explanation: >-
      Congenital hearing defects are among the subphenotypes significantly more
      common in late-truncating variants; an overall cohort frequency is not
      given, so no frequency band is assigned.
- category: Craniofacial
  name: Dental Anomalies
  description: >-
    Teeth abnormalities are common, including previously reported abnormal
    peg-shaped teeth.
  phenotype_term:
    preferred_term: Dental anomalies
    term:
      id: HP:0000164
      label: Abnormality of the dentition
  frequency: FREQUENT
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "teeth abnormalities were common."
    explanation: >-
      The cohort documents teeth abnormalities as common.
- category: Cardiovascular
  name: Patent Ductus Arteriosus
  description: >-
    Patent ductus arteriosus, together with patent foramen ovale, constitutes
    the "persistence of fetal anatomy" cardiac category reported in 19% of the
    cohort.
  phenotype_term:
    preferred_term: Patent ductus arteriosus
    term:
      id: HP:0001643
      label: Patent ductus arteriosus
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most frequent are septal defects including atrial septal defects (34%),
      ventricular septal defects in (8%), and persistence of the fetal anatomy
      (19%) (patent foreman ovale, and persistent ductus arteriosus).
    explanation: >-
      Persistent ductus arteriosus is part of the persistence-of-fetal-anatomy
      category reported in 19% of the cohort (combined with patent foramen ovale).
- category: Cardiovascular
  name: Patent Foramen Ovale
  description: >-
    Patent foramen ovale, together with patent ductus arteriosus, constitutes
    the "persistence of fetal anatomy" cardiac category reported in 19% of the
    cohort.
  phenotype_term:
    preferred_term: Patent foramen ovale
    term:
      id: HP:0001655
      label: Patent foramen ovale
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most frequent are septal defects including atrial septal defects (34%),
      ventricular septal defects in (8%), and persistence of the fetal anatomy
      (19%) (patent foreman ovale, and persistent ductus arteriosus).
    explanation: >-
      Patent foramen ovale is part of the persistence-of-fetal-anatomy category
      reported in 19% of the cohort (combined with patent ductus arteriosus).
- category: Ophthalmologic
  name: Amblyopia
  description: >-
    Amblyopia is reported in several patients, and is more likely when
    strabismus is unrecognized and untreated.
  phenotype_term:
    preferred_term: Amblyopia
    term:
      id: HP:0000646
      label: Amblyopia
  frequency: VERY_RARE
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Amblyopia is reported in several patients."
    explanation: >-
      The cohort documents amblyopia in several patients, an uncommon secondary
      complication of strabismus.
- category: Genitourinary
  name: Cryptorchidism
  description: >-
    Undescended testes are reported in a small number of male patients.
  phenotype_term:
    preferred_term: Cryptorchidism
    term:
      id: HP:0000028
      label: Cryptorchidism
  frequency: VERY_RARE
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we found a small number of patients had undescended testes (boys),
      clinodactyly and/or brachydactyly.
    explanation: >-
      The cohort documents undescended testes in a small number of male patients.

genetic:
- name: KAT6A Pathogenic Variants
  gene_term:
    preferred_term: KAT6A
    term:
      id: hgnc:13013
      label: KAT6A
  association: Causative
  presence: Positive
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    Heterozygous pathogenic KAT6A variants are usually de novo and predominantly
    protein-truncating (nonsense or frameshift), with recurrent hotspots in the
    arginine-rich acidic domain (amino acid positions 1019, 1024, 1129). Variant
    position drives an allele-dependent molecular consequence: early-truncating
    variants (exons 1-15) are predicted to trigger NMD and haploinsufficiency
    and are associated with milder disease, whereas late-truncating variants
    (exons 16-17) escape NMD and are associated with more severe disease.
    Missense variants are reported but require variant-specific functional
    evidence.
  inheritance:
  - name: Autosomal dominant inheritance
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    description: >-
      Arboleda-Tham syndrome is autosomal dominant and almost always caused by a
      de novo KAT6A variant.
    evidence:
    - reference: PMID:25728775
      reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Here, we report a syndrome caused by de novo heterozygous nonsense
        mutations in KAT6A (a.k.a., MOZ, MYST3) identified by clinical exome
        sequencing (CES) in four independent families.
      explanation: >-
        The founding series establishes de novo heterozygous KAT6A variants as
        causal.
  evidence:
  - reference: PMID:25728777
    reference_title: "Dominant mutations in KAT6A cause intellectual disability with recognizable syndromic features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Finally, by detailed clinical characterization we provide evidence that
      heterozygous mutations in KAT6A cause a distinct intellectual disability
      syndrome.
    explanation: >-
      Establishes KAT6A as the causative gene for a distinct intellectual
      disability syndrome.
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our analysis identifies hotspot nonsense mutations within the penultimate
      exons at amino acid positions 1019, 1024, and 1129 that account for 19.1%
      (13/68) of pathogenic variants in unrelated individuals.
    explanation: >-
      Quantifies the recurrent truncating hotspots that make up a substantial
      fraction of pathogenic variants.

diagnosis:
- name: Exome or genome sequencing
  description: >-
    Diagnosis is molecular. Because the clinical features overlap many
    developmental syndromes and there is no single pathognomonic feature,
    identification of a heterozygous pathogenic KAT6A variant by exome (or
    genome) sequencing, typically trio-based to establish de novo status,
    establishes the diagnosis.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  results: >-
    A heterozygous pathogenic or likely pathogenic KAT6A variant confirms the
    diagnosis.
  evidence:
  - reference: PMID:25728775
    reference_title: "De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "identified by clinical exome sequencing (CES) in four independent families"
    explanation: >-
      The founding series identified the disorder by clinical exome sequencing.
  - reference: PMID:25728777
    reference_title: "Dominant mutations in KAT6A cause intellectual disability with recognizable syndromic features."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with mutations in KAT6A/MOZ detected by whole-exome sequencing"
    explanation: >-
      An independent series likewise established the diagnosis by whole-exome
      sequencing.
- name: Baseline cardiac evaluation
  description: >-
    Given the high prevalence of cardiac lesions, baseline cardiology assessment
    with echocardiography is recommended at diagnosis.
  diagnosis_term:
    preferred_term: clinical assessment
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  results: >-
    Echocardiography identifies septal defects and persistence of fetal anatomy
    that may require intervention.
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The prevalence of cardiac lesions highlights the need for early cardiology
      assessment.
    explanation: >-
      The cohort recommends early cardiology assessment given the cardiac-lesion
      prevalence.

treatments:
- name: Multidisciplinary Supportive Care
  description: >-
    Management is symptomatic and individualized, coordinating developmental,
    nutritional, gastrointestinal, cardiac, ophthalmologic, and
    infectious-disease care. Early cardiology assessment with echocardiography is
    recommended given the high prevalence of cardiac lesions.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  therapeutic_modality: OTHER
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The prevalence of cardiac lesions highlights the need for early cardiology
      assessment.
    explanation: >-
      The cohort recommends early cardiology assessment as part of
      individualized multidisciplinary care.
  target_phenotypes:
  - preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
- name: Speech and Language Therapy
  description: >-
    Speech and language therapy, augmented by sign language and communication
    aids, addresses the universal expressive speech delay and verbal dyspraxia.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: speech therapy
    term:
      id: NCIT:C159273
      label: Speech Language Therapy
  therapeutic_modality: BEHAVIORAL
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Use of sign language and communication aids are helpful."
    explanation: >-
      The cohort supports communication-focused intervention for the
      characteristic expressive speech delay.
  target_phenotypes:
  - preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
- name: Cardiac Surgical or Catheter Intervention
  description: >-
    A substantial proportion of patients with cardiac malformations require
    intervention by open-heart surgery or cardiac catheterization.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: septal defect repair
    term:
      id: NCIT:C148075
      label: Septal Defect Repair
  therapeutic_modality: SURGERY
  evidence:
  - reference: PMID:30245513
    reference_title: "KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At least 45% of patients with cardiac malformations required intervention
      (open heart surgery or via cardiac catheterization).
    explanation: >-
      The cohort documents cardiac intervention in at least 45% of patients with
      cardiac malformations.
  target_phenotypes:
  - preferred_term: Atrial septal defect
    term:
      id: HP:0001631
      label: Atrial septal defect
- name: Pantothenate and L-Carnitine Supplementation
  description: >-
    An experimental, preclinical intervention. In patient-derived fibroblast
    models of KAT6A syndrome, pantothenate plus L-carnitine increased histone
    acetylation, partially corrected protein and transcriptomic expression
    patterns, and improved cell bioenergetics. This is in vitro evidence only
    and has not been evaluated as a clinical therapy.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: nutritional supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: pantothenate
      term:
        id: CHEBI:16454
        label: pantothenate
    - preferred_term: L-carnitine
      term:
        id: CHEBI:16347
        label: (R)-carnitine
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Mitochondrial and Bioenergetic Dysfunction
    treatment_effect: RESTORES
    description: >-
      Pantothenate (a CoA precursor) and L-carnitine act as mitochondrial
      boosting agents that improve the impaired cell bioenergetics of
      KAT6A-mutant fibroblasts in vitro; this is the mechanistic rationale for
      the intervention.
  evidence:
  - reference: PMID:36553567
    reference_title: "Pantothenate and L-Carnitine Supplementation Improves Pathological Alterations in Cellular Models of KAT6A Syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Pantothenate and L-carnitine treatment increased histone acetylation and
      partially corrected protein and transcriptomic expression patterns in
      mutant KAT6A cells.
    explanation: >-
      Patient-derived fibroblast models show that pantothenate and L-carnitine
      partially correct KAT6A-associated cellular abnormalities, an experimental
      preclinical lead.
📚

References & Deep Research

References

6
De novo nonsense mutations in KAT6A, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay.
No top-level findings curated for this source.
Dominant mutations in KAT6A cause intellectual disability with recognizable syndromic features.
No top-level findings curated for this source.
KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants.
No top-level findings curated for this source.
Neuropsychological profile associated with KAT6A syndrome: Emergent genotype-phenotype trends.
No top-level findings curated for this source.
KAT6A deficiency impairs cognitive functions through suppressing RSPO2/Wnt signaling in hippocampal CA3.
No top-level findings curated for this source.
Pantothenate and L-Carnitine Supplementation Improves Pathological Alterations in Cellular Models of KAT6A Syndrome.
No top-level findings curated for this source.

Deep Research

1
Falcon
Arboleda–Tham Syndrome (KAT6A Syndrome): Comprehensive Disease-Characteristics Report
Edison Scientific Literature 35 citations 2026-07-30T23:55:35.801042

Arboleda–Tham Syndrome (KAT6A Syndrome): Comprehensive Disease-Characteristics Report

Executive summary

Arboleda–Tham syndrome (ARTHS), more commonly called KAT6A syndrome, is a rare autosomal-dominant Mendelian chromatinopathy caused by heterozygous pathogenic variants in KAT6A, a lysine acetyltransferase and transcriptional regulator. The defining phenotype is congenital or early-childhood neurodevelopmental impairment—particularly severe expressive speech delay—with variable hypotonia, feeding and gastrointestinal dysfunction, characteristic craniofacial features, eye abnormalities, congenital heart disease, microcephaly, growth impairment, sleep disturbance, behavioral differences, and occasional seizures. Most affected individuals have a de novo protein-truncating variant; late truncations in exons 16–17 tend to produce a more severe phenotype than earlier truncations. The best available cohort contained 76 individuals aged 1–32 years, so population prevalence, adult natural history, life expectancy, and formal quality-of-life outcomes remain poorly defined. (kennedy2019kat6asyndromegenotype–phenotype pages 8-9, kennedy2019kat6asyndromegenotype–phenotype pages 1-2)

The strongest recent mechanistic advance is a 2024 mouse study identifying a KAT6A→RSPO2→Wnt/β-catenin pathway in hippocampal CA3 pyramidal neurons. Kat6a deficiency reduced CA3 synaptic structure and plasticity and impaired memory; AAV-mediated restoration of RSPO2 substantially rescued the molecular, synaptic, and behavioral deficits. This is important proof of biological reversibility but not yet a human treatment. (liu2024kat6adeficiencyimpairs pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2)

The following compact table summarizes high-yield knowledge-base annotations; ontology mappings are suggestions and should be validated against the release used by the target database.

domain evidence-backed finding suggested ontology identifiers/terms evidence type/strength
disease entity Arboleda-Tham syndrome / KAT6A syndrome; Mendelian chromatinopathy / neurodevelopmental disorder caused by pathogenic KAT6A variants; disease-level resource also represented as “autosomal dominant intellectual disability-craniofacial anomalies-cardiac defects syndrome” (bae2021identificationofa pages 1-2, arboleda2015denovononsense pages 1-2, OpenTargets Search: Arboleda-Tham syndrome-KAT6A) Suggested: MONDO:0014558; OMIM/MIM: 616268; category: Mendelian disorder Strong: discovery paper + curated disease-target resource + later case series/cohort
causal gene Causal gene is KAT6A (aka MOZ, MYST3), encoding lysine acetyltransferase 6A; gene MIM 601408 (bae2021identificationofa pages 1-2, munueracabeza2022pantothenateandlcarnitine pages 1-2, arboleda2015denovononsense pages 1-2) Suggested: HGNC gene KAT6A; OMIM/MIM: 601408 Strong: multiple human genetic studies
inheritance Predominantly autosomal dominant, usually de novo heterozygous variants; one maternally inherited missense/VUS-like situation reported in cohort work, supporting variable expressivity for some missense alleles (bae2021identificationofa pages 1-2, lin2020diagnosisofarboledatham pages 3-4, kennedy2019kat6asyndromegenotype–phenotype pages 2-3, arboleda2015denovononsense pages 1-2) Suggested: HP:0000006 Autosomal dominant inheritance; HP:0025352 De novo constitutional mutation Strong for AD/de novo; moderate for broader penetrance/expressivity nuances
core neurodevelopment Global developmental delay / intellectual disability is essentially universal in compiled cohorts (100%); speech delay is especially prominent (99%) and often the most severe developmental domain (urreizti2020fivenewcases pages 7-8, kennedy2019kat6asyndromegenotype–phenotype pages 8-9, kennedy2019kat6asyndromegenotype–phenotype pages 6-7) Suggested: HP:0001263 Global developmental delay; HP:0001249 Intellectual disability; HP:0002463 Global developmental delay/variable severity; HP:0000750 Delayed speech and language development Strong: largest cohort + case series
feeding / GI phenotype Feeding difficulties in infancy are common (79%), often with reflux, constipation, and oromotor dysfunction; bowel malrotation/obstruction risk highlighted in management recommendations (urreizti2020fivenewcases pages 7-8, bae2021identificationofa pages 5-6, kennedy2019kat6asyndromegenotype–phenotype pages 6-7) Suggested: HP:0011968 Feeding difficulties; HP:0002020 Gastroesophageal reflux; HP:0002019 Constipation; MAXO suggested: feeding support / laxative therapy / GI surveillance Strong for feeding/constipation; moderate for obstruction risk
hypotonia Neonatal hypotonia reported in 74% and contributes to early motor delay and feeding issues (urreizti2020fivenewcases pages 7-8, lin2020diagnosisofarboledatham pages 3-4) Suggested: HP:0001290 Generalized hypotonia; HP:0008947 Infantile muscular hypotonia Strong: cohort-supported
craniofacial / ear phenotype Ear anomalies are frequent (83%); characteristic dysmorphism includes bulbous/prominent nose, thin upper lip, low-set ears, epicanthal folds, frontal bossing, long face/midface retrusion in some patients (urreizti2020fivenewcases pages 7-8, bae2021identificationofa pages 5-6, urreizti2020fivenewcases pages 6-7) Suggested: HP:0000357 Abnormality of the external ear; HP:0000369 Low-set ears; HP:0000426 Prominent nasal bridge; HP:0000219 Thin upper lip vermilion Moderate-strong: cohort + repeated case reports
ophthalmic phenotype Eye anomalies occur in 72%; strabismus/visual issues affect over half of the cohort and may risk amblyopia if untreated (urreizti2020fivenewcases pages 7-8, bae2021identificationofa pages 5-6, kennedy2019kat6asyndromegenotype–phenotype pages 6-7) Suggested: HP:0000478 Abnormality of the eye; HP:0000486 Strabismus; HP:0000505 Visual impairment; MAXO suggested: ophthalmology surveillance Strong for broad eye involvement; moderate for specific subfeatures
microcephaly Microcephaly reported in 36% overall; was a prominent feature in the original discovery series (urreizti2020fivenewcases pages 7-8, arboleda2015denovononsense pages 1-2) Suggested: HP:0000252 Microcephaly Strong
cardiac phenotype Congenital heart disease occurs in about 50%, commonly septal defects/PDA/PFO; about half of affected cardiac cases required surgical intervention in the large cohort (bae2021identificationofa pages 5-6, kennedy2019kat6asyndromegenotype–phenotype pages 6-7, lin2020diagnosisofarboledatham pages 3-4) Suggested: HP:0001627 Abnormality of the cardiovascular system; HP:0001631 Atrial septal defect; HP:0001643 Patent ductus arteriosus; MAXO suggested: echocardiography / cardiology evaluation / cardiac surgery Strong for frequency and need for baseline cardiac workup
seizures / sleep Seizures reported in 13% and sleep disturbance in 42% in compiled cohort data (urreizti2020fivenewcases pages 7-8) Suggested: HP:0001250 Seizure; HP:0002360 Sleep disturbance Moderate: cohort-supported but less deeply characterized
genotype spectrum Most variants are truncating; in 52 novel cases, 88% (39/44) were predicted truncating. Recurrent hotspot truncations occur at aa 1019, 1024, 1129; recurrent nonsense variants include p.Arg1024 and p.Arg1129 (kennedy2019kat6asyndromegenotype–phenotype pages 1-2, kennedy2019kat6asyndromegenotype–phenotype pages 2-3, arboleda2015denovononsense pages 1-2) Suggested: SO terms—nonsense_variant, frameshift_variant, splice_donor/acceptor_variant, missense_variant Strong
genotype-phenotype correlation Late-truncating variants in exons 16–17 associate with more severe ID/speech problems and more microcephaly, hypotonia, cardiac and GI complications; early truncating variants likely undergo NMD and may have fewer GI symptoms (bae2021identificationofa pages 1-2, bae2021identificationofa pages 5-6, kennedy2019kat6asyndromegenotype–phenotype pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2) Suggested: exon 16/17 late-truncating subgroup annotation; mechanism note: escape from NMD vs haploinsufficiency Moderate-strong: cohort-based correlation, still mechanistically incomplete
primary anatomy Main affected systems are central nervous system, heart, gastrointestinal tract, eye, craniofacial structures, and growth pathways (bae2021identificationofa pages 1-2, kennedy2019kat6asyndromegenotype–phenotype pages 6-7, liu2024kat6adeficiencyimpairs pages 1-2, arboleda2015denovononsense pages 1-2) Suggested UBERON: brain, hippocampus, heart, gastrointestinal tract, eye, craniofacial skeleton Strong at organ-system level
cell types Experimental evidence points especially to hippocampal CA3 pyramidal excitatory neurons for cognitive mechanism; patient-derived dermal fibroblasts are established disease cell models (munueracabeza2022pantothenateandlcarnitine pages 1-2, liu2024kat6adeficiencyimpairs pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2, arboleda2015denovononsense pages 6-7) Suggested CL terms: excitatory neuron, pyramidal neuron, fibroblast Strong for model systems; moderate for direct human tissue causality
subcellular / chromatin localization KAT6A is a chromatin-associated lysine acetyltransferase recruited to unmethylated CpG islands via an N-terminal winged-helix DNA-binding domain; affects histone acetylation including H3K9 and H3K23 contexts (weber2023thehistoneacetyltransferase pages 1-2, arboleda2015denovononsense pages 6-7) Suggested GO CC/BP: nucleus, chromatin, histone acetyltransferase complex, regulation of transcription by RNA polymerase II; histone marks: H3K9ac, H3K23ac/propionylation context Strong biochemistry/mechanism
core mechanism Best current mechanistic chain: KAT6A deficiency → reduced transcription of CA3-enriched RSPO2 → impaired Wnt/β-catenin signaling in hippocampal CA3 → reduced dendritic spine density / synaptic plasticity → hippocampus-dependent memory deficits (liu2024kat6adeficiencyimpairs pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2) Suggested GO/BP: histone acetylation; positive regulation of Wnt signaling pathway; synaptic plasticity; learning or memory. Suggested pathway label: KAT6A–RSPO2–Wnt axis Strong preclinical evidence; not yet fully validated in humans
additional molecular abnormalities Patient fibroblasts show altered histone acetylation (decreased H3K9ac, increased H3K18ac in original work), altered p53-related expression, transcriptomic disruption, and mitochondrial/bioenergetic defects with reduced acetylation/deacetylation, CoA-metabolism and antioxidant proteins (munueracabeza2022pantothenateandlcarnitine pages 15-16, arboleda2015denovononsense pages 6-7) Suggested GO/BP: regulation of apoptotic process, cellular metabolism, mitochondrial function, oxidative stress response Moderate: human in vitro evidence from small numbers
diagnostics Diagnosis is primarily by WES/WGS, especially trio-based testing for de novo variants; WGS and WES both successfully diagnosed infants/children with syndromic developmental delay and dysmorphism (bae2021identificationofa pages 1-2, lin2020diagnosisofarboledatham pages 3-4, lin2020diagnosisofarboledatham pages 1-3, arboleda2015denovononsense pages 1-2) Suggested testing annotations: trio WES, trio WGS, Sanger confirmation; phenotype-driven genomic testing Strong
supportive management Current management is supportive and surveillance-based: early developmental assessment/intervention, speech-language therapy and communication aids/sign language, cardiology evaluation with ECG/echocardiogram, GI management for reflux/constipation/feeding issues, ophthalmology review, rehabilitation and serial developmental follow-up (bae2021identificationofa pages 5-6, bae2021identificationofa pages 6-7, kennedy2019kat6asyndromegenotype–phenotype pages 6-7) Suggested MAXO: developmental therapy, speech therapy, augmentative communication, cardiology assessment, ophthalmologic monitoring, GI symptom management, rehabilitation Moderate-strong: expert cohort recommendations rather than trials
experimental interventions No established disease-specific therapy retrieved. Preclinical/cellular candidates: pantothenate + L-carnitine improved histone acetylation, transcriptomic/protein abnormalities and bioenergetics in three patient fibroblast lines; RSPO2 restoration / Wnt enhancement rescued synaptic and behavioral phenotypes in mouse CA3 (munueracabeza2022pantothenateandlcarnitine pages 1-2, munueracabeza2022pantothenateandlcarnitine pages 15-16, liu2024kat6adeficiencyimpairs pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2) Suggested CHEBI/MAXO notes: pantothenate supplementation, L-carnitine supplementation, AAV-mediated RSPO2 restoration, Wnt-pathway enhancement Weak-moderate for translation: preclinical only
model organisms Kat6a homozygous knockout mice are embryonic lethal with developmental/vascular-cardiac and hematopoietic defects; haploinsufficient and neuron-specific mouse models reproduce growth and cognitive phenotypes; AAV rescue supports reversibility of some neural deficits (munueracabeza2022pantothenateandlcarnitine pages 1-2, liu2024kat6adeficiencyimpairs pages 1-2, arboleda2015denovononsense pages 6-7) Suggested model annotations: mouse knockout, conditional neuronal knockout, AAV rescue model Strong for disease-mechanism modeling
epidemiology / demographics Largest cohort included 76 patients, age 1–32 years, sex roughly balanced (49% female, 51% male). True population prevalence/incidence remain undefined; one report estimated pathogenic KAT6A variants in ~1% of undiagnosed syndromic developmental delay referrals, which is not a population prevalence estimate (kennedy2019kat6asyndromegenotype–phenotype pages 1-2, bae2021identificationofa pages 5-6, arboleda2015denovononsense pages 1-2) Suggested epidemiology note: prevalence unknown; ascertainment from case reports/cohorts, not population registry Moderate for cohort demographics; weak for prevalence
evidence gaps Major gaps: no robust population prevalence/incidence, no disease-specific survival/life-expectancy data, sparse formal QoL studies, limited penetrance estimates, no validated biomarkers for monitoring, no established episignature data in retrieved full texts, no controlled treatment trials, and little evidence for environmental/protective factors or gene-environment interaction (kennedy2019kat6asyndromegenotype–phenotype pages 1-2, kennedy2019kat6asyndromegenotype–phenotype pages 6-7, kennedy2019kat6asyndromegenotype–phenotype pages 9-10) Suggested annotation: evidence gap / not established / not retrieved Strong confidence that these are current knowledge gaps based on gathered evidence

Table: This table compiles the highest-yield, evidence-backed annotations for Arboleda-Tham/KAT6A syndrome using only the information gathered in the preceding search. It is useful as a compact knowledge-base scaffold spanning identifiers, phenotype frequencies, mechanism, diagnostics, management, and evidence gaps.

1. Disease information

Definition and identifiers

  • Preferred names: Arboleda–Tham syndrome; KAT6A syndrome.
  • Alternative names: autosomal dominant intellectual disability–craniofacial anomalies–cardiac defects syndrome; autosomal dominant mental retardation 32; KAT6A-related neurodevelopmental disorder.
  • MONDO: MONDO:0014558, represented as autosomal dominant intellectual disability–craniofacial anomalies–cardiac defects syndrome.
  • OMIM phenotype: 616268.
  • Causal gene: KAT6A, OMIM gene 601408, also known as MOZ and MYST3; Ensembl target ENSG00000083168.
  • Chromosomal location: 8p11.21/8p11 region.
  • ICD-10/ICD-11 and MeSH: no syndrome-specific code or descriptor was established in the retrieved evidence. Coding generally must use broader congenital-malformation, intellectual-disability, or genetic-syndrome categories. (OpenTargets Search: Arboleda-Tham syndrome-KAT6A, bae2021identificationofa pages 1-2, lin2020diagnosisofarboledatham pages 3-4)

The syndrome was delineated in 2015 after clinical trio-exome sequencing identified de novo heterozygous nonsense variants in four unrelated families. The discovery abstract states: “Common features among all four probands include primary microcephaly, global developmental delay including profound speech delay, and craniofacial dysmorphism.” [Arboleda et al., published March 5, 2015; DOI: https://doi.org/10.1016/j.ajhg.2015.01.017]. (arboleda2015denovononsense pages 1-2)

Evidence provenance

The evidence is principally aggregated disease-level information derived from individually ascertained patients, including clinician reports, family surveys, case reports, exome/genome cohorts, and literature review. It is not based on a population registry or systematic extraction from longitudinal electronic health records. The largest study combined 52 new cases with previously published individuals for a total of 76. (kennedy2019kat6asyndromegenotype–phenotype pages 1-2)

2. Etiology

Causal and genetic risk factors

ARTHS is caused by a heterozygous constitutional pathogenic variant in KAT6A. Most reported variants are nonsense or frameshift alleles, although splice-site and selected missense variants have also been described. In the 2019 cohort, 39/44 novel variants (88%) were predicted truncating. Recurrent nonsense hotspots at amino-acid positions 1019, 1024, and 1129 accounted for 13/68 (19.1%) pathogenic variants among unrelated individuals. (kennedy2019kat6asyndromegenotype–phenotype pages 8-9, kennedy2019kat6asyndromegenotype–phenotype pages 2-3)

Examples include:

  • NM_006766.5:c.3385C>T, p.Arg1129Ter, recurrent in the discovery series;
  • c.3070C>T, p.Arg1024Ter;
  • NM_006766.5:c.3411del, p.Glu1139SerfsTer41, a de novo exon-17 variant associated with severe delay;
  • c.1312C>T, p.Arg438Ter, an early truncating variant expected to undergo nonsense-mediated decay;
  • c.3427_3428insTA, p.Ser1143LeufsTer5;
  • c.1075G>A, p.Gly359Ser, which experimentally altered splicing rather than acting solely as a missense allele. (bae2021identificationofa pages 1-2, lin2020diagnosisofarboledatham pages 3-4, urreizti2020fivenewcases pages 7-8, arboleda2015denovononsense pages 1-2)

Pathogenic constitutional variants are expected to be absent or extremely rare from population databases because of strong functional constraint and severe early-onset effects. Exact gnomAD/TOPMed frequencies were not available in the retrieved texts and should be obtained variant-by-variant rather than inferred.

Environmental, infectious, and lifestyle risk factors

No toxin, infection, radiation, diet, smoking, alcohol, occupation, or other lifestyle exposure is known to cause ARTHS. It is not infectious or environmentally acquired. Phenotypic variability may reflect genetic background, epigenetic state, development, clinical ascertainment, and possibly environment, but no reproducible gene–environment interaction has been demonstrated. The 2019 cohort explicitly considered background genetic variation and environmental factors plausible contributors to expressivity, not established causal exposures. (kennedy2019kat6asyndromegenotype–phenotype pages 9-10, arboleda2015denovononsense pages 6-7)

Protective factors and modifiers

No validated protective allele, modifier gene, diet, or exposure is known. KAT6B may provide partial biochemical redundancy in some tissues, but this is mechanistic inference rather than a clinically established modifier. Pantothenate and L-carnitine improved cellular abnormalities in vitro; they have not been shown to prevent disease or improve outcomes in patients. (munueracabeza2022pantothenateandlcarnitine pages 1-2, liu2024kat6adeficiencyimpairs pages 8-9)

3. Phenotypes

The most reusable frequencies come from the 76-person cohort and the subsequent synthesis of approximately 80 reported cases. Denominators vary because not every feature was assessed in every patient; percentages should therefore be stored with study provenance rather than treated as population penetrance. (urreizti2020fivenewcases pages 7-8, kennedy2019kat6asyndromegenotype–phenotype pages 1-2)

Phenotype Frequency/current characterization Onset/course and functional impact Suggested HPO term
Global developmental delay/intellectual disability Approximately 100%; severity variable Infancy/early childhood; chronic and lifelong; affects learning, independence, and adaptive function HP:0001263; HP:0001249
Speech/language delay Approximately 99%; expressive speech disproportionately severe May become clearer after infancy; often persistent and a major participation barrier HP:0000750; consider childhood apraxia/motor-speech annotation when formally diagnosed
Neonatal/infantile hypotonia Approximately 74% Early onset; may worsen feeding and motor milestone acquisition HP:0001290 / HP:0008947
Feeding difficulty Approximately 79% Usually infancy; oromotor dysfunction, reflux, and poor growth may require tube feeding HP:0011968
Gastroesophageal reflux/constipation Common, exact denominator variable Usually chronic or recurrent; constipation may require long-term treatment HP:0002020; HP:0002019
Congenital heart disease About 50%; septal defects and PDA/PFO common Congenital and generally structurally stable after treatment; about half of cardiac cases required surgery HP:0001627; HP:0001631; HP:0001643
Eye abnormalities About 72%; strabismus/visual problems in over half Childhood; untreated strabismus can lead to permanent amblyopia HP:0000478; HP:0000486; HP:0000505
External-ear anomalies About 83% Congenital, usually nonprogressive HP:0000357; HP:0000369
Microcephaly About 36% overall Congenital or postnatal; severity variable HP:0000252
Characteristic face Broad/bulbous nasal tip or prominent bridge, thin/tented upper lip, low-set ears, epicanthi, short philtrum, frontal bossing or midface retrusion Congenital; facial gestalt may evolve with age HP:0000426; HP:0000219; HP:0000286
Sleep disturbance About 42% Childhood; potentially chronic/fluctuating and burdensome to families HP:0002360
Seizures About 13% Variable onset and type; not a universal defining feature HP:0001250
Behavioral/autistic features Autism reported at approximately 25% in one synthesis; stereotypies and other behavioral differences vary Childhood; effects on education and social function vary HP:0000729; HP:0000717
Skeletal abnormalities Scoliosis, kyphosis, torticollis, syndactyly, pes planus, genu valgum; craniosynostosis around 10% in one synthesis Congenital or developing with growth; may affect mobility or require surgery Feature-specific HPO terms
Genitourinary findings Cryptorchidism in some males; inguinal hernia reported Congenital HP:0000028; HP:0000023
Recurrent infections Reported in case series, frequency uncertain Episodic; immune mechanism not established HP:0002719

These estimates are supported by the five-case/literature synthesis reporting developmental delay/ID 100%, speech delay 99%, feeding difficulty 79%, neonatal hypotonia 74%, ear anomalies 83%, eye anomalies 72%, microcephaly 36%, seizures 13%, and sleep disturbance 42%. (urreizti2020fivenewcases pages 7-8) Congenital heart disease occurs in approximately half, and feeding difficulties were estimated at 78.7% in another review. (bae2021identificationofa pages 5-6, kennedy2019kat6asyndromegenotype–phenotype pages 6-7)

Quality of life

No validated ARTHS-specific EQ-5D, SF-36, PROMIS, or caregiver-burden dataset was identified. The major inferred burdens are impaired communication, intellectual and adaptive limitations, feeding support, constipation, visual disability, sleep disruption, mobility problems, and repeated specialty care. Communication aids and early speech therapy are therefore clinically important even in the absence of controlled quality-of-life trials. (bae2021identificationofa pages 6-7, kennedy2019kat6asyndromegenotype–phenotype pages 6-7)

4. Genetic and molecular information

Gene and protein

KAT6A encodes a roughly 250-kDa MYST-family lysine acetyltransferase. Important regions include an N-terminal NEMM/winged-helix region, a double PHD finger, the catalytic histone-acetyltransferase domain, and long acidic and serine/methionine-rich C-terminal regions. KAT6A operates in multiprotein chromatin complexes with BRPF-family scaffolds, ING4/ING5, and MEAF6/EAF6-associated components. It modifies histone and non-histone substrates, including p53. (arboleda2015denovononsense pages 6-7, weber2023thehistoneacetyltransferase pages 1-2)

Variant classes and consequences

  • Early truncating variants, exons 1–15: commonly expected to trigger nonsense-mediated mRNA decay and produce haploinsufficiency.
  • Late truncating variants, exons 16–17: may escape nonsense-mediated decay, leaving truncated proteins with altered C-terminal regulatory functions. The cohort association with greater severity raises dominant-negative or altered-function possibilities, but these mechanisms are not fully proven in patients.
  • Canonical splice variants: pathogenic when demonstrated to disrupt splicing.
  • Missense variants: require cautious evaluation. De novo status, absence from population databases, domain/residue conservation, phenotype concordance, functional evidence, and an ARTHS-compatible methylation signature can strengthen classification. A maternally inherited p.Ser371Tyr allele was classified as a VUS in the 2019 study. (kennedy2019kat6asyndromegenotype–phenotype pages 8-9, kennedy2019kat6asyndromegenotype–phenotype pages 2-3, liu2024kat6adeficiencyimpairs pages 1-2)

Variants causing the developmental syndrome are germline/constitutional, not somatic. Somatic KAT6A rearrangements or fusions are relevant to leukemia but are a separate disease mechanism and should not be conflated with ARTHS.

Genotype–phenotype relationship

Late truncations in exons 16–17 correlate with more severe intellectual disability, speech impairment, microcephaly, neonatal hypotonia, cardiac anomalies, and gastrointestinal complications. Early truncations may have fewer gastrointestinal manifestations. This is a group-level association, not a deterministic prognostic rule. (bae2021identificationofa pages 1-2, bae2021identificationofa pages 5-6, kennedy2019kat6asyndromegenotype–phenotype pages 8-9)

Epigenetics and chromosomal abnormalities

The syndrome is itself an epigenetic-regulator disorder. Patient fibroblasts showed reduced H3K9 acetylation and increased H3K18 acetylation in the original study, with altered p53-pathway expression. A later cellular study also found reduced histone-H3 acetylation, broad transcriptomic disturbance, and mitochondrial/bioenergetic abnormalities. (munueracabeza2022pantothenateandlcarnitine pages 15-16, arboleda2015denovononsense pages 6-7)

A 2023 publication reported sensitive and specific blood DNA-methylation episignatures for KAT6A/KAT6B variants, suggesting a future adjunct for VUS interpretation; however, the full study was not retrievable in this search, so assay performance should be verified directly before database entry or clinical use [Vos et al., Epigenomics, May 2023; DOI: https://doi.org/10.2217/epi-2023-0079].

No recurrent pathogenic aneuploidy, translocation, inversion, or syndrome-defining copy-number alteration is established as the usual cause. Deletions disrupting KAT6A could theoretically cause haploinsufficiency, but larger 8p alterations may produce blended phenotypes.

5. Environmental information

No environmental toxin, radiation exposure, pollutant, occupational factor, lifestyle behavior, or infectious agent is known to initiate ARTHS. Standard healthy diet, activity, vaccination, and avoidance of tobacco exposure remain appropriate general health measures but are not disease-specific prevention. Nutrient-dependent acetyl-CoA and mitochondrial biology may influence cellular acetylation, yet no clinical evidence establishes diet as a modifier of penetrance or severity. (munueracabeza2022pantothenateandlcarnitine pages 1-2, munueracabeza2022pantothenateandlcarnitine pages 15-16)

6. Mechanism and pathophysiology

Upstream molecular lesion

A pathogenic KAT6A allele reduces the amount of functional enzyme or yields a C-terminally truncated dysfunctional protein. KAT6A normally binds chromatin and catalyzes lysine acetylation, helping establish transcriptionally competent chromatin. A 2023 biochemical study showed that an N-terminal winged-helix domain directly recognizes unmethylated CpG motifs and recruits KAT6A to CpG islands genome-wide. Mutating essential DNA-binding residues abolished CpG-island enrichment; a winged-helix mutant also exerted a dominant-negative effect on H3K9 acetylation. (weber2023thehistoneacetyltransferase pages 1-2)

Downstream chromatin and cellular effects

The original patient-fibroblast study found altered H3K9/H3K18 acetylation and differential expression of 30 p53-pathway genes, enriched for apoptosis, transcriptional regulation, and metabolism. The authors concluded that KAT6A variants alter global acetylation and p53-mediated pathways. (arboleda2015denovononsense pages 6-7)

Fibroblasts from three patients subsequently showed reduced H3 acetylation and reduced proteins involved in acetylation/deacetylation, CoA metabolism, mitochondrial function, and antioxidant defense, including SIRT1, SIRT3, NAMPT, PANK2, mitochondrial respiratory-chain proteins, SOD1/SOD2, and GPX4. These findings support secondary mitochondrial and redox dysfunction, but fibroblasts are a surrogate model and do not establish that every abnormality occurs in human neurons or heart tissue. (munueracabeza2022pantothenateandlcarnitine pages 1-2, munueracabeza2022pantothenateandlcarnitine pages 15-16)

KAT6A–RSPO2–Wnt causal chain in the brain

The best-defined neural mechanism is:

KAT6A haploinsufficiency → reduced H3K23 acetylation at the Rspo2 promoter and reduced Rspo2 transcription → diminished RSPO2-dependent canonical Wnt/β-catenin signaling → reduced dendritic-spine density, excitatory transmission, and long-term potentiation in CA3 pyramidal neurons → impaired hippocampus-dependent learning and memory.

Single-nucleus RNA sequencing and chromatin analysis identified Rspo2 as the robust CA3-enriched transcriptional target. Excitatory-neuron Rspo2 deletion phenocopied Kat6a loss, whereas AAV-RSPO2 delivery restored β-catenin, synaptic physiology, dendritic spines, and much of the learning/memory phenotype. CA1 synaptic function was comparatively spared. (liu2024kat6adeficiencyimpairs pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2)

Direct abstract quote: “Deletion of Rspo2 in excitatory neurons impairs memory formation, and restoring RSPO2 expression in CA3 neurons rescues the deficits in Wnt signaling and learning-associated behaviors in Kat6a mutant mice.” [Liu et al., Science Advances, May 17, 2024; DOI: https://doi.org/10.1126/sciadv.adm9326]. (liu2024kat6adeficiencyimpairs pages 1-2)

Suggested ontologies

  • GO biological process: histone acetylation; chromatin organization; regulation of transcription by RNA polymerase II; canonical Wnt signaling; synaptic plasticity; learning or memory; stem-cell maintenance; embryonic organ development.
  • GO cellular component: nucleus; chromatin; histone acetyltransferase complex; neuronal dendrite; excitatory synapse.
  • Cell Ontology: fibroblast; excitatory neuron; pyramidal neuron; hippocampal CA3 pyramidal neuron where an exact release-specific term exists; hematopoietic stem cell; neural-crest-derived craniofacial cell as a proposed developmental annotation.

Omics and advanced technologies

Human fibroblast RNA-seq demonstrated transcriptomic disturbance; the 2024 mouse study integrated single-nucleus RNA-seq with chromatin analysis. No validated human disease-specific proteomic, metabolomic, lipidomic, spatial-transcriptomic, organoid, or large iPSC atlas was identified. No published therapeutic CRISPR screen was retrieved. (munueracabeza2022pantothenateandlcarnitine pages 1-2, liu2024kat6adeficiencyimpairs pages 1-2, arboleda2015denovononsense pages 6-7)

7. Anatomical structures affected

  • Primary nervous-system involvement: developing brain and neural circuits governing cognition, speech, language, motor planning, tone, sleep, and behavior. The strongest mechanistic localization is hippocampal CA3, not evidence that disease is restricted to CA3.
  • Cardiovascular: atrial/ventricular septa, ductus arteriosus, and other congenital cardiac structures.
  • Gastrointestinal/oromotor: oral and pharyngeal feeding apparatus, esophagus, bowel motility, and occasionally intestinal rotation/obstruction.
  • Craniofacial: skull, palate, midface, nose, lips, jaw, and external ears.
  • Eye: extraocular alignment and visual system; ptosis and structural ocular abnormalities occur variably.
  • Musculoskeletal: spine, feet, joints, and cranial sutures in a subset.
  • Genitourinary: testes/inguinal region in some males.
  • Hematopoietic/immune system: major defects occur in complete mouse knockouts; recurrent infection and an isolated 2023 marrow-failure report warrant awareness, but routine human hematopoietic failure is not established. (lin2020diagnosisofarboledatham pages 3-4, urreizti2020fivenewcases pages 7-8, kennedy2019kat6asyndromegenotype–phenotype pages 6-7, arboleda2015denovononsense pages 6-7)

Suggested UBERON annotations include brain, hippocampus, CA3 field of hippocampus, heart, gastrointestinal tract, eye, palate, craniofacial skeleton, spinal column, and testis. Relevant subcellular annotations are nucleus, chromatin, nucleosome, and histone-acetyltransferase complex. No consistent lateralization is known.

8. Temporal development

ARTHS begins prenatally through disturbed embryonic gene regulation, although the neurodevelopmental phenotype often becomes clinically apparent in infancy. Congenital manifestations can include craniofacial differences, heart defects, palate abnormalities, hypotonia, feeding difficulty, growth restriction, and microcephaly. Developmental and especially expressive-language delays become clearer over the first years; an infant diagnosed at two months developed evident expressive-language delay by eight months. (bae2021identificationofa pages 1-2, bae2021identificationofa pages 6-7)

The disorder is chronic and lifelong. It has no accepted staging system, relapsing-remitting pattern, or spontaneous remission phenotype. Congenital structural abnormalities are generally stable or surgically corrected, while development continues slowly with variable gains. Constipation, sleep problems, orthopedic abnormalities, and communication disability may remain chronic. One individual had progressive cerebellar atrophy, but progressive neurodegeneration is not established as the typical course. (urreizti2020fivenewcases pages 7-8)

Early childhood is the principal intervention window for feeding safety, communication, motor development, vision, and cardiac assessment. Early genomic diagnosis therefore has practical value even without disease-modifying therapy. (bae2021identificationofa pages 6-7, kennedy2019kat6asyndromegenotype–phenotype pages 6-7)

9. Inheritance and population

Inheritance is autosomal dominant and usually de novo. For an affected individual with a constitutional pathogenic variant, the theoretical transmission risk is 50% per pregnancy, although reproductive fitness and individual circumstances vary. Parents testing negative in blood usually have a low recurrence risk, but parental germline or low-level somatic mosaicism cannot be excluded; no syndrome-specific mosaic recurrence rate is available.

Penetrance appears high for truncating pathogenic variants ascertained clinically, while expressivity is markedly variable. Missense alleles require greater caution because incomplete penetrance, alternate molecular effects, or misclassification may occur. Genetic anticipation is not expected because ARTHS is not a repeat-expansion disorder. Consanguinity is not etiologically relevant to a predominantly de novo dominant condition. No founder variant, carrier frequency, or population-specific enrichment is established. (kennedy2019kat6asyndromegenotype–phenotype pages 8-9, kennedy2019kat6asyndromegenotype–phenotype pages 2-3, kennedy2019kat6asyndromegenotype–phenotype pages 9-10)

The largest cohort included 76 individuals aged 1–32 years and was sex-balanced: 49% female and 51% male. Cases have been reported across multiple ancestries and regions; no geographic or ethnic predilection is established. Approximately 400–500 diagnosed patients had been cited by 2023–2024 mechanistic publications, but this is a reported-case count, not prevalence. A discovery-center estimate of 3/298, approximately 1%, among developmental-delay exomes reflects highly selected referral ascertainment and must not be interpreted as population prevalence. (kennedy2019kat6asyndromegenotype–phenotype pages 1-2, liu2024kat6adeficiencyimpairs pages 1-2, arboleda2015denovononsense pages 6-7, weber2023thehistoneacetyltransferase pages 1-2)

Population prevalence, birth incidence, and carrier frequency remain unknown.

10. Diagnostics

Clinical recognition

Clinical suspicion should arise with global developmental delay—especially profound expressive speech delay—plus hypotonia, feeding/GI problems, a broad or bulbous nose with thin upper lip, low-set ears, eye findings, microcephaly, or congenital heart disease. No purely clinical diagnostic criteria are sufficiently specific; molecular confirmation is required.

Recommended genetic approach

  1. Trio WES or WGS is the preferred broad approach for an undiagnosed syndromic neurodevelopmental disorder. WES identified the original de novo variants; WGS diagnosed a severe case within four weeks and may detect structural, noncoding, or coverage-limited variants missed by exome sequencing. (lin2020diagnosisofarboledatham pages 1-3, arboleda2015denovononsense pages 1-2)
  2. Neurodevelopmental/intellectual-disability or congenital-anomaly panels should include KAT6A and detect single-nucleotide variants and indels, with validated exon-level copy-number analysis.
  3. Single-gene sequencing is suitable when the phenotype is strongly suggestive or for familial testing.
  4. Confirm the variant and parental status by an orthogonal method such as Sanger sequencing where appropriate.
  5. Interpret variants using ACMG/AMP criteria, population frequency, predicted loss of function, exon position/NMD, de novo status, phenotype, splicing assays, and functional or methylation evidence.
  6. CMA remains useful when a copy-number disorder is suspected or sequencing is nondiagnostic. Routine karyotype/FISH, mitochondrial DNA testing, and repeat-expansion testing are not first-line ARTHS tests.

RNA sequencing can resolve suspected splice variants, while blood DNA-methylation profiling may support classification of uncertain KAT6A/KAT6B variants. Neither replaces primary DNA testing.

Baseline and surveillance evaluations

Recommended evaluations include developmental and speech-language assessment; feeding/swallowing and nutrition review; growth and head circumference; ECG and echocardiogram; ophthalmology; hearing; neurologic assessment with EEG when seizures are suspected; GI review for reflux, constipation, malrotation, or obstruction; musculoskeletal examination; and renal/genitourinary assessment guided by findings. Brain MRI is clinically indicated for seizures, abnormal neurologic progression, unusual head growth, or focal findings, not as a diagnostic biomarker. (bae2021identificationofa pages 5-6, kennedy2019kat6asyndromegenotype–phenotype pages 6-7)

Differential diagnosis

Important differentials include KAT6B-related Say–Barber–Biesecker–Young–Simpson/genitopatellar syndromes, BRPF1-related intellectual developmental disorder with dysmorphic facies and ptosis, Wiedemann–Steiner syndrome, Kabuki syndrome, Coffin–Siris spectrum, Cornelia de Lange spectrum, Rubinstein–Taybi syndrome, CDK13-related disorder, and other monogenic chromatinopathies. Distinction generally requires genomic testing because ID, speech delay, hypotonia, feeding problems, heart defects, and dysmorphism overlap.

Population newborn screening is unavailable. Cascade testing is appropriate after a molecular diagnosis; prenatal diagnosis and preimplantation genetic testing are technically possible when the familial variant is known.

11. Outcome and prognosis

No reliable 5- or 10-year survival rate, disease-specific mortality rate, or life-expectancy estimate exists. The 2019 cohort included adults up to age 32, showing survival into adulthood, but adult ascertainment is limited. (kennedy2019kat6asyndromegenotype–phenotype pages 1-2)

Morbidity is dominated by communication and intellectual disability, delayed motor and adaptive skills, feeding/GI problems, visual impairment, sleep disturbance, and congenital anomalies. Developmental skills may improve with therapy, but full recovery from the underlying neurodevelopmental disorder is not expected. Prognostic factors supported at group level include variant position—late truncations generally confer greater severity—and the burden of congenital heart, GI, feeding, neurologic, or orthopedic complications. Individual prediction remains imprecise because expressivity varies even among people with the same variant. (kennedy2019kat6asyndromegenotype–phenotype pages 8-9, arboleda2015denovononsense pages 6-7)

There is no validated circulating, imaging, electrophysiologic, or molecular prognostic biomarker. DNA methylation signatures are diagnostic/classification candidates rather than proven outcome biomarkers.

12. Treatment

Current clinical management

There is no approved disease-modifying pharmacotherapy, gene therapy, RNA therapy, or cell therapy. Care is multidisciplinary and phenotype-directed:

  • early intervention, special education, neuropsychology, and behavioral support;
  • intensive speech-language therapy, with sign language, picture systems, or speech-generating devices introduced early rather than waiting for speech to emerge;
  • physical and occupational therapy for hypotonia, coordination, mobility, and adaptive skills;
  • swallow/feeding therapy, nutritional support, reflux treatment, and enteral feeding when required;
  • constipation therapy and urgent evaluation of bilious vomiting or obstructive symptoms;
  • standard cardiology and cardiac-surgical care;
  • ophthalmologic treatment of strabismus, refractive error, ptosis, and amblyopia risk;
  • standard antiseizure therapy when epilepsy is confirmed;
  • sleep assessment and treatment of specific contributors;
  • orthopedic, craniofacial, dental, hearing, and genitourinary care as indicated. (bae2021identificationofa pages 5-6, bae2021identificationofa pages 6-7, kennedy2019kat6asyndromegenotype–phenotype pages 6-7)

Suggested MAXO annotations include genetic counseling, exome/genome sequencing, echocardiography, electrocardiography, ophthalmologic examination, developmental assessment, speech therapy, augmentative and alternative communication, physical therapy, occupational therapy, feeding therapy, enteral nutrition, laxative therapy, antiseizure pharmacotherapy, and corrective cardiac or craniofacial surgery.

Experimental strategies

Patient fibroblasts treated with pantothenate and L-carnitine showed increased histone acetylation, partial normalization of protein and transcriptomic patterns, and significantly improved bioenergetics. Direct abstract quote: “Pantothenate and L-carnitine treatment increased histone acetylation and partially corrected protein and transcriptomic expression patterns in mutant KAT6A cells.” [Munuera-Cabeza et al., published December 2022; DOI: https://doi.org/10.3390/genes13122300]. This was an in-vitro study of three patient cell lines, not a clinical trial; efficacy, dosing, safety, and developmental benefit in patients are unknown. (munueracabeza2022pantothenateandlcarnitine pages 1-2, munueracabeza2022pantothenateandlcarnitine pages 15-16)

Enhancing RSPO2/Wnt signaling rescued cognitive and synaptic deficits in mice, identifying a target rather than a ready treatment. Systemic Wnt activation has substantial developmental and oncogenic risks, and human translation will require tissue-specific delivery and extensive safety work. (liu2024kat6adeficiencyimpairs pages 8-9)

No disease-specific interventional ClinicalTrials.gov study was retrieved. There are therefore no evidence-based response rates, adverse-event profiles, combination regimens, or pharmacogenomic prescribing recommendations for ARTHS.

13. Prevention

Primary prevention by lifestyle modification or vaccination is not possible for a usually de novo genetic disorder. The principal preventive actions are reproductive and complication-focused:

  • preconception and postdiagnostic genetic counseling;
  • parental testing, with discussion of residual germline-mosaicism risk;
  • prenatal diagnosis or PGT-M when a pathogenic familial variant is known;
  • early molecular diagnosis and developmental intervention;
  • baseline cardiac and eye assessment to prevent avoidable cardiac morbidity and amblyopia;
  • feeding/swallowing assessment to reduce malnutrition and aspiration risk;
  • proactive constipation treatment and recognition of bowel obstruction;
  • seizure, sleep, orthopedic, and hearing surveillance according to symptoms.

No population carrier-screening or newborn-screening program is indicated by current evidence. Public-health sanitation, vector control, environmental remediation, vaccines, and antimicrobial prophylaxis are not disease-specific measures.

14. Other species and natural disease

No naturally occurring veterinary syndrome clearly orthologous to human ARTHS was identified, and there is no zoonotic or cross-species transmission. Relevant orthologues include mouse Kat6a and zebrafish kat6a; exact NCBI Gene and Taxon identifiers should be populated from current NCBI records. Standard taxonomy identifiers are Homo sapiens Taxon 9606, Mus musculus Taxon 10090, and Danio rerio Taxon 7955.

KAT6A’s chromatin, embryonic-development, hematopoietic, cardiac, craniofacial, and neural functions are evolutionarily conserved. Animal phenotypes are experimental genetic models rather than evidence of a recognized spontaneous livestock, companion-animal, or wildlife disease. (arboleda2015denovononsense pages 6-7, weber2023thehistoneacetyltransferase pages 1-2)

15. Model organisms and experimental systems

Mouse models

  • Constitutive homozygous Kat6a loss: embryonic or perinatal lethal, with vascular/cardiac, gastrointestinal, skeletal, thymic/splenic, neural-stem-cell, and hematopoietic defects. This model demonstrates essential developmental functions but is more severe than the usual human heterozygous syndrome. (arboleda2015denovononsense pages 6-7)
  • Kat6a+/− early-truncation model: approximately 50% hippocampal Kat6a expression, reduced body weight, and learning/memory abnormalities, modeling human haploinsufficiency.
  • Excitatory-neuron conditional knockout: reproduces CA3-specific synaptic and memory deficits without requiring whole-organism loss.
  • Rspo2 conditional knockout and AAV-RSPO2 rescue: establish pathway causality and demonstrate that selected postnatal neural deficits can be reversed in mice. (liu2024kat6adeficiencyimpairs pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2)

Limitations include species differences, simplified alleles, incomplete modeling of late-truncating human variants, and inability of behavioral assays to reproduce human speech, language, congenital anomalies, and psychosocial outcomes.

Cellular and biochemical models

Patient dermal fibroblasts reproduce altered histone acetylation, p53-related transcription, mitochondrial dysfunction, and treatment-responsive molecular phenotypes. Their accessibility is an advantage, but they do not fully model developing neurons, cardiomyocytes, cranial neural crest, or gastrointestinal tissues. Recombinant-domain, DNA-binding, chromatin-immunoprecipitation, and genome-wide occupancy assays established direct KAT6A recruitment to unmethylated CpG islands. (munueracabeza2022pantothenateandlcarnitine pages 1-2, arboleda2015denovononsense pages 6-7, weber2023thehistoneacetyltransferase pages 1-2)

No mature ARTHS-specific iPSC-neuron, cerebral-organoid, or patient-derived cardiac-organoid platform was identified in the retrieved literature; these are logical priorities for variant-specific therapeutic testing.

Recent developments, 2023–2024

  1. Chromatin targeting: KAT6A was shown to bind unmethylated CpG islands directly through an N-terminal winged-helix domain, clarifying how the enzyme reaches genomic targets [published online December 20, 2022; journal issue 2023; DOI: https://doi.org/10.1093/nar/gkac1188]. (weber2023thehistoneacetyltransferase pages 1-2)
  2. DNA-methylation diagnostics: a 2023 study reported KAT6A/KAT6B episignatures as sensitive and specific biomarkers for variant detection/classification; direct review is needed for exact validation metrics [DOI: https://doi.org/10.2217/epi-2023-0079].
  3. Brain mechanism and rescue: the 2024 Science Advances study localized a major cognitive mechanism to CA3 KAT6A–RSPO2–Wnt signaling and achieved AAV-RSPO2 rescue [DOI: https://doi.org/10.1126/sciadv.adm9326]. (liu2024kat6adeficiencyimpairs pages 8-9, liu2024kat6adeficiencyimpairs pages 1-2)
  4. Phenotypic expansion: 2024 reports added prenatal/fetal observations, including fetal hepatic calcification, and additional Asian cases, but these remain isolated observations rather than established screening markers [DOIs: https://doi.org/10.1016/j.ejmg.2023.104906 and https://doi.org/10.1002/mgg3.2420].
  5. Clinical implementation: multidisciplinary chromatinopathy clinics increasingly integrate genomic sequencing, DNA-methylation profiling, anticipatory surveillance, and structured neurodevelopmental care; however, controlled ARTHS treatment trials remain absent.

Evidence assessment and major gaps

The gene–disease relationship and core phenotype are strongly supported by repeated de novo variants, recurrence, variant enrichment, and consistent human phenotypes. Genotype–phenotype correlation is moderately strong but subject to ascertainment and incomplete standardized testing. Cellular acetylation and metabolic abnormalities have direct human in-vitro support but small sample sizes. The CA3 RSPO2/Wnt mechanism has unusually strong preclinical causal evidence—including conditional genetics and rescue—but has not been demonstrated in human brain tissue or clinical intervention.

Priority gaps are population prevalence, adult natural history, formal adaptive and quality-of-life trajectories, penetrance of nontruncating variants, systematic immune/hematologic surveillance data, human neuronal and organoid models, validated longitudinal biomarkers, and controlled therapeutic trials. Consequently, experimental supplements or pathway-directed interventions should not be represented as established therapy.

References

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  13. (bae2021identificationofa pages 5-6): Soyoung Bae, Aram Yang, Jinsup Kim, Hyun Ju Lee, and Hyun Kyung Park. Identification of a novel kat6a variant in an infant presenting with facial dysmorphism and developmental delay: a case report and literature review. BMC Medical Genomics, Dec 2021. URL: https://doi.org/10.1186/s12920-021-01148-x, doi:10.1186/s12920-021-01148-x. This article has 22 citations and is from a peer-reviewed journal.

  14. (urreizti2020fivenewcases pages 6-7): Roser Urreizti, Estrella Lopez-Martin, Antonio Martinez-Monseny, Montse Pujadas, Laura Castilla-Vallmanya, Luis Alberto Pérez-Jurado, Mercedes Serrano, Daniel Natera-de Benito, Beatriz Martínez-Delgado, Manuel Posada-de-la-Paz, Javier Alonso, Purificación Marin-Reina, Mar O’Callaghan, Daniel Grinberg, Eva Bermejo-Sánchez, and Susanna Balcells. Five new cases of syndromic intellectual disability due to kat6a mutations: widening the molecular and clinical spectrum. Orphanet Journal of Rare Diseases, Feb 2020. URL: https://doi.org/10.1186/s13023-020-1317-9, doi:10.1186/s13023-020-1317-9. This article has 48 citations and is from a peer-reviewed journal.

  15. (arboleda2015denovononsense pages 6-7): Valerie A. Arboleda, Hane Lee, Naghmeh Dorrani, Neda Zadeh, Mary Willis, Colleen Forsyth Macmurdo, Melanie A. Manning, Andrea Kwan, Louanne Hudgins, Florian Barthelemy, M. Carrie Miceli, Fabiola Quintero-Rivera, Sibel Kantarci, Samuel P. Strom, Joshua L. Deignan, Wayne W. Grody, Eric Vilain, and Stanley F. Nelson. De novo nonsense mutations in kat6a, a lysine acetyl-transferase gene, cause a syndrome including microcephaly and global developmental delay. American journal of human genetics, 96 3:498-506, Mar 2015. URL: https://doi.org/10.1016/j.ajhg.2015.01.017, doi:10.1016/j.ajhg.2015.01.017. This article has 172 citations and is from a highest quality peer-reviewed journal.

  16. (weber2023thehistoneacetyltransferase pages 1-2): Lisa Marie Weber, Yulin Jia, Bastian Stielow, Stephen S Gisselbrecht, Yinghua Cao, Yanpeng Ren, Iris Rohner, Jessica King, Elisabeth Rothman, Sabrina Fischer, Clara Simon, Ignasi Forné, Andrea Nist, Thorsten Stiewe, Martha L Bulyk, Zhanxin Wang, and Robert Liefke. The histone acetyltransferase kat6a is recruited to unmethylated cpg islands via a dna binding winged helix domain. Nucleic Acids Research, 51:574-594, Dec 2023. URL: https://doi.org/10.1093/nar/gkac1188, doi:10.1093/nar/gkac1188. This article has 44 citations and is from a highest quality peer-reviewed journal.

  17. (munueracabeza2022pantothenateandlcarnitine pages 15-16): Manuel Munuera-Cabeza, Mónica Álvarez-Córdoba, Juan Suárez-Rivero, Suleva Povea-Cabello, Irene Villalón-García, Marta Talaverón-Rey, Alejandra Suárez-Carrillo, Diana Reche-López, Paula Cilleros-Holgado, Rocío Piñero-Pérez, and José Sánchez-Alcázar. Pantothenate and l-carnitine supplementation improves pathological alterations in cellular models of kat6a syndrome. Genes, 13:2300, Dec 2022. URL: https://doi.org/10.3390/genes13122300, doi:10.3390/genes13122300. This article has 6 citations.

  18. (lin2020diagnosisofarboledatham pages 1-3): Yung-Feng Lin, Tzu-Ching Lin, Ralph Kirby, Hui-Ying Weng, Yen-Ming Liu, Dau-Ming Niu, Shih-Feng Tsai, and Chia-Feng Yang. Diagnosis of arboleda-tham syndrome by whole genome sequencing in an asian boy with severe developmental delay. Molecular Genetics and Metabolism Reports, 25:100686, Dec 2020. URL: https://doi.org/10.1016/j.ymgmr.2020.100686, doi:10.1016/j.ymgmr.2020.100686. This article has 22 citations.

  19. (bae2021identificationofa pages 6-7): Soyoung Bae, Aram Yang, Jinsup Kim, Hyun Ju Lee, and Hyun Kyung Park. Identification of a novel kat6a variant in an infant presenting with facial dysmorphism and developmental delay: a case report and literature review. BMC Medical Genomics, Dec 2021. URL: https://doi.org/10.1186/s12920-021-01148-x, doi:10.1186/s12920-021-01148-x. This article has 22 citations and is from a peer-reviewed journal.

  20. (kennedy2019kat6asyndromegenotype–phenotype pages 9-10): Joanna Kennedy, David Goudie, Edward Blair, Kate Chandler, Shelagh Joss, Victoria McKay, Andrew Green, Ruth Armstrong, Melissa Lees, Benjamin Kamien, Bruce Hopper, Tiong Yang Tan, Patrick Yap, Zornitza Stark, Nobuhiko Okamoto, Noriko Miyake, Naomichi Matsumoto, Ellen Macnamara, Jennifer L. Murphy, Elizabeth McCormick, Hakon Hakonarson, Marni J. Falk, Dong Li, Patrick Blackburn, Eric Klee, Dusica Babovic-Vuksanovic, Susan Schelley, Louanne Hudgins, Sarina Kant, Bertrand Isidor, Benjamin Cogne, Kimberley Bradbury, Mark Williams, Chirag Patel, Helen Heussler, Celia Duff-Farrier, Phillis Lakeman, Ingrid Scurr, Usha Kini, Mariet Elting, Margot Reijnders, Janneke Schuurs-Hoeijmakers, Mohamed Wafik, Anne Blomhoff, Claudia A.L. Ruivenkamp, Esther Nibbeling, Alexander J.M. Dingemans, Emilie D. Douine, Stanley F. Nelson, Maja Hempel, Tatjana Bierhals, Davor Lessel, Jessika Johannsen, Valerie A. Arboleda, and Ruth Newbury-Ecob. Kat6a syndrome: genotype–phenotype correlation in 76 patients with pathogenic kat6a variants. Genetics in Medicine, 21:850-860, Apr 2019. URL: https://doi.org/10.1038/s41436-018-0259-2, doi:10.1038/s41436-018-0259-2. This article has 134 citations and is from a highest quality peer-reviewed journal.

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