Hao-Fountain syndrome is a rare USP7-related autosomal dominant neurodevelopmental disorder characterized by speech impairment, cognitive dysfunction, behavioral abnormalities, and multisystem developmental features. Available evidence supports USP7 haploinsufficiency with downstream chromatin-associated regulatory dysfunction.
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name: Hao-Fountain syndrome
creation_date: "2026-04-15T15:45:03Z"
description: >-
Hao-Fountain syndrome is a rare USP7-related autosomal dominant
neurodevelopmental disorder characterized by speech impairment, cognitive
dysfunction, behavioral abnormalities, and multisystem developmental
features. Available evidence supports USP7 haploinsufficiency with
downstream chromatin-associated regulatory dysfunction.
category: Mendelian
parents:
- hereditary disease
- neurodevelopmental disorder
disease_term:
preferred_term: Hao-Fountain syndrome
term:
id: MONDO:0014805
label: Hao-Fountain syndrome
inheritance:
- name: Autosomal dominant inheritance
description: >-
Hao-Fountain syndrome is an autosomal dominant disorder caused by
pathogenic USP7 variants.
inheritance_term:
preferred_term: Autosomal dominant inheritance
term:
id: HP:0000006
label: Autosomal dominant inheritance
evidence:
- reference: DOI:10.3389/fcell.2026.1782599
reference_title: >-
Integrative epigenetic and transcriptomic profiling of whole blood and
fibroblasts in Hao-Fountain syndrome
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Hao–Fountain syndrome (HAFOUS) is a rare autosomal dominant
neurodevelopmental disorder caused by pathogenic USP7 variants.
explanation: This directly supports autosomal dominant inheritance and USP7 causality.
pathophysiology:
- name: USP7 haploinsufficiency
description: >-
Reduced USP7 dosage is the initiating molecular lesion in Hao-Fountain
syndrome and perturbs several cellular homeostatic mechanisms, including
functions linked to the MUST complex.
genes:
- preferred_term: USP7
term:
id: hgnc:12630
label: USP7
evidence:
- reference: DOI:10.3389/fcell.2026.1782599
reference_title: >-
Integrative epigenetic and transcriptomic profiling of whole blood and
fibroblasts in Hao-Fountain syndrome
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
USP7 haploinsufficiency is associated with a restricted set of regulatory
loci enriched within PRC1-associated chromatin domains.
explanation: This directly supports USP7 haploinsufficiency as the initiating molecular defect.
- reference: PMID:38221796
reference_title: "Hao-Fountain syndrome: 32 novel patients reveal new insights into the clinical spectrum."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Hao-Fountain syndrome (HAFOUS, OMIM: #616863) is a neurodevelopmental disorder caused by pathogenic variants in the gene USP7 coding for USP7, a protein involved in several crucial cellular homeostatic mechanisms and the recently described MUST complex."
explanation: This provides partial mechanistic context that USP7 participates in broader homeostatic and MUST-complex-associated functions relevant to Hao-Fountain syndrome.
downstream:
- target: PRC1-associated chromatin dysregulation
description: Reduced USP7 dosage perturbs PRC1-associated chromatin regulation.
causal_link_type: DIRECT
evidence:
- reference: DOI:10.3389/fcell.2026.1782599
reference_title: >-
Integrative epigenetic and transcriptomic profiling of whole blood and
fibroblasts in Hao-Fountain syndrome
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
USP7 haploinsufficiency is associated with a restricted set of regulatory
loci enriched within PRC1-associated chromatin domains.
explanation: This directly links USP7 haploinsufficiency to PRC1-associated chromatin dysregulation.
- name: PRC1-associated chromatin dysregulation
description: >-
Hao-Fountain syndrome shows methylation and expression abnormalities within
PRC1-associated chromatin domains and developmental genes.
biological_processes:
- preferred_term: chromatin remodeling
modifier: ABNORMAL
term:
id: GO:0006338
label: chromatin remodeling
- preferred_term: regulation of transcription by RNA polymerase II
modifier: ABNORMAL
term:
id: GO:0006357
label: regulation of transcription by RNA polymerase II
evidence:
- reference: DOI:10.3389/fcell.2026.1782599
reference_title: >-
Integrative epigenetic and transcriptomic profiling of whole blood and
fibroblasts in Hao-Fountain syndrome
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Fibroblasts revealed coherent methylation and expression changes at
developmental genes, whereas blood captured the diagnostic episignature
and a smaller set of downstream regulatory alterations.
explanation: This directly supports downstream chromatin-associated regulatory dysregulation in Hao-Fountain syndrome.
downstream:
- target: Global developmental delay
description: Developmental regulatory dysfunction contributes to global developmental delay.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "global developmental delay, intellectual disability, severe speech delay"
explanation: Orphanet's definition lists global developmental delay among the central clinical manifestations.
- target: Intellectual disability
description: Developmental regulatory dysfunction contributes to cognitive impairment.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "global developmental delay, intellectual disability, severe speech delay"
explanation: Orphanet's definition lists intellectual disability among the central clinical manifestations.
- target: Borderline intellectual functioning
description: Cognitive dysfunction is often borderline on average, with some individuals reaching the range of intellectual disability.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: PMID:38221796
reference_title: "Hao-Fountain syndrome: 32 novel patients reveal new insights into the clinical spectrum."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Cognitive testing reports reveal borderline intellectual functioning on average, although some individuals score in the range of intellectual disability.
explanation: The expanded cohort supports borderline intellectual functioning as part of the cognitive spectrum.
- target: Delayed speech and language development
description: Neurodevelopmental dysregulation contributes to prominent speech impairment.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "severe speech delay"
explanation: Orphanet's definition lists severe speech delay among the central manifestations.
- target: Behavioral abnormality
description: Developmental regulatory dysfunction contributes to characteristic behavioral differences.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "behavioral abnormalities (including impulsivity, compulsivity, stubbornness"
explanation: Orphanet's definition lists behavioral abnormalities and examples.
- target: Autism
description: Developmental regulatory dysfunction contributes to autistic features.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "autism spectrum disorder"
explanation: Orphanet's definition lists autism spectrum disorder.
- target: Abnormal facial shape
description: Developmental dysregulation contributes to the dysmorphic phenotype.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "mild and variable dysmorphic facies"
explanation: Orphanet's definition lists dysmorphic facies.
- target: Hypotonia
description: Neurodevelopmental dysfunction can include hypotonia.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "Patients may also have hypotonia"
explanation: Orphanet's definition lists hypotonia among additional patient features.
- target: Feeding difficulties
description: Neurodevelopmental dysfunction can include feeding problems.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "hypotonia, feeding problems"
explanation: Orphanet's definition lists feeding problems among additional patient features.
- target: Seizure
description: Neurodevelopmental dysfunction can include seizures.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "hypogonadism in males, seizures and ocular anomalies"
explanation: Orphanet's definition lists seizures among additional patient features.
- target: Hyperphagia
description: Developmental dysregulation contributes to appetite and weight abnormalities in a subset of affected individuals.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
evidence:
- reference: PMID:38221796
reference_title: "Hao-Fountain syndrome: 32 novel patients reveal new insights into the clinical spectrum."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In addition to confirming previously described features, we report hyperphagia and increased body weight in a subset of individuals.
explanation: The expanded cohort supports hyperphagia in a subset of individuals.
phenotypes:
- name: Delayed speech and language development
category: Neurologic
diagnostic: true
description: Speech impairment is a major and potentially hallmark feature of Hao-Fountain syndrome.
phenotype_term:
preferred_term: Delayed speech and language development
term:
id: HP:0000750
label: Delayed speech and language development
evidence:
- reference: PMID:38221796
reference_title: "Hao-Fountain syndrome: 32 novel patients reveal new insights into the clinical spectrum."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Speech impairment emerges as a potential hallmark of Hao-Fountain
syndrome.
explanation: This directly supports speech impairment as a central syndrome feature.
- name: Intellectual disability
category: Neurologic
description: Cognitive dysfunction ranges from borderline intellectual functioning to intellectual disability in Hao-Fountain syndrome.
phenotype_term:
preferred_term: Intellectual disability
term:
id: HP:0001249
label: Intellectual disability
evidence:
- reference: PMID:35627274
reference_title: >-
Complex Presentation of Hao-Fountain Syndrome Solved by Exome Sequencing
Highlighting Co-Occurring Genomic Variants.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
A 20-year-old woman affected by moderate intellectual disability (ID),
dysmorphic features, hypertrichosis, scoliosis, recurrent bronchitis, and
pneumonia with bronchiectasis, colelithiasis, chronic severe
constipation, and a family history suggestive of autosomal dominant
recurrence of polycystic kidney disease was analyzed by WES to identify
the genomic events underlying the condition.
explanation: This directly supports intellectual disability as a clinical manifestation of Hao-Fountain syndrome.
- reference: PMID:38221796
reference_title: "Hao-Fountain syndrome: 32 novel patients reveal new insights into the clinical spectrum."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Cognitive testing reports reveal borderline intellectual functioning on average, although some individuals score in the range of intellectual disability.
explanation: This provides partial support for intellectual disability while clarifying that cognitive impairment spans a broader spectrum in the larger cohort.
- name: Borderline intellectual functioning
category: Neurologic
description: Cognitive function is often borderline on average in Hao-Fountain syndrome.
phenotype_term:
preferred_term: Borderline intellectual functioning
term:
id: HP:0006889
label: Borderline intellectual disability
evidence:
- reference: PMID:38221796
reference_title: "Hao-Fountain syndrome: 32 novel patients reveal new insights into the clinical spectrum."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Cognitive testing reports reveal borderline intellectual functioning on average, although some individuals score in the range of intellectual disability.
explanation: This directly supports borderline intellectual disability as the average cognitive phenotype in the larger cohort.
- name: Behavioral abnormality
category: Neurologic
description: Distinctive behavioral abnormalities are part of the Hao-Fountain syndrome phenotype.
phenotype_term:
preferred_term: Behavioral abnormality
term:
id: HP:0000708
label: Atypical behavior
evidence:
- reference: PMID:35627274
reference_title: >-
Complex Presentation of Hao-Fountain Syndrome Solved by Exome Sequencing
Highlighting Co-Occurring Genomic Variants.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
A de novo truncating USP7 variant was disclosed as the cause of
Hao-Fountain syndrome, a disorder characterized by syndromic ID and
distinctive behavior.
explanation: This directly supports behavioral abnormality as part of the Hao-Fountain syndrome phenotype.
- name: Abnormal facial shape
category: Morphological
description: Dysmorphic facial features are common in Hao-Fountain syndrome.
phenotype_term:
preferred_term: Abnormal facial shape
term:
id: HP:0001999
label: Abnormal facial shape
evidence:
- reference: PMID:35627274
reference_title: >-
Complex Presentation of Hao-Fountain Syndrome Solved by Exome Sequencing
Highlighting Co-Occurring Genomic Variants.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
A 20-year-old woman affected by moderate intellectual disability (ID),
dysmorphic features, hypertrichosis, scoliosis, recurrent bronchitis, and
pneumonia with bronchiectasis, colelithiasis, chronic severe
constipation, and a family history suggestive of autosomal dominant
recurrence of polycystic kidney disease was analyzed by WES to identify
the genomic events underlying the condition.
explanation: This directly supports dysmorphic facial features as part of the Hao-Fountain syndrome phenotype.
- name: Hyperphagia
category: Metabolic
description: Hyperphagia with increased body weight is reported in a subset of individuals with Hao-Fountain syndrome.
phenotype_term:
preferred_term: Hyperphagia
term:
id: HP:0002591
label: Polyphagia
evidence:
- reference: PMID:38221796
reference_title: "Hao-Fountain syndrome: 32 novel patients reveal new insights into the clinical spectrum."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In addition to confirming previously described features, we report hyperphagia and increased body weight in a subset of individuals.
explanation: This directly supports hyperphagia as part of the expanded Hao-Fountain syndrome phenotype spectrum.
- name: Global developmental delay
category: Neurologic
diagnostic: true
description: Global developmental delay is a central early neurodevelopmental manifestation of Hao-Fountain syndrome.
phenotype_term:
preferred_term: Global developmental delay
term:
id: HP:0001263
label: Global developmental delay
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "global developmental delay, intellectual disability, severe speech delay"
explanation: Orphanet's definition lists global developmental delay among the central manifestations.
- name: Autism
category: Neurologic
description: Autism spectrum disorder is part of the core neurobehavioral phenotype.
phenotype_term:
preferred_term: Autism spectrum disorder
term:
id: HP:0000717
label: Autism
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "autism spectrum disorder"
explanation: Orphanet's definition lists autism spectrum disorder.
- name: Hypotonia
category: Neurologic
description: Hypotonia is reported among additional Hao-Fountain syndrome features.
phenotype_term:
preferred_term: Hypotonia
term:
id: HP:0001252
label: Hypotonia
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "Patients may also have hypotonia"
explanation: Orphanet's definition lists hypotonia.
- name: Feeding difficulties
category: Gastrointestinal
description: Feeding problems are part of the broader developmental presentation.
phenotype_term:
preferred_term: Feeding difficulties
term:
id: HP:0011968
label: Feeding difficulties
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "hypotonia, feeding problems"
explanation: Orphanet's definition lists feeding problems.
- name: Seizure
category: Neurologic
description: Seizures are reported in a subset of individuals with Hao-Fountain syndrome.
phenotype_term:
preferred_term: Seizure
term:
id: HP:0001250
label: Seizure
evidence:
- reference: ORPHA:643549
reference_title: "Hao-Fountain syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "hypogonadism in males, seizures and ocular anomalies"
explanation: Orphanet's definition lists seizures.
biochemical: []
genetic:
- name: USP7
association: Causal haploinsufficient variant
gene_term:
preferred_term: USP7
term:
id: hgnc:12630
label: USP7
notes: >-
Hao-Fountain syndrome is caused by pathogenic USP7 variants, including de
novo truncating alleles.
evidence:
- reference: PMID:35627274
reference_title: >-
Complex Presentation of Hao-Fountain Syndrome Solved by Exome Sequencing
Highlighting Co-Occurring Genomic Variants.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
A de novo truncating USP7 variant was disclosed as the cause of
Hao-Fountain syndrome, a disorder characterized by syndromic ID and
distinctive behavior.
explanation: This directly supports USP7 as the causal gene for Hao-Fountain syndrome.
- reference: CGGV:assertion_7e4961fa-f972-4e82-ac29-a511ff954529-2021-09-03T182145.545Z
reference_title: "USP7 / Hao-Fountain syndrome (Definitive)"
supports: SUPPORT
evidence_source: OTHER
snippet: "USP7 | HGNC:12630 | Hao-Fountain syndrome | MONDO:0014805 | AD | Definitive"
explanation: ClinGen classifies the USP7-Hao-Fountain syndrome gene-disease relationship as definitive with autosomal dominant inheritance.
environmental: []
treatments: []
diagnosis:
- name: USP7 molecular genetic testing
description: Exome sequencing or targeted molecular testing that identifies a pathogenic USP7 variant confirms the diagnosis.
presence: Identification of a pathogenic USP7 variant confirms the diagnosis.
diagnosis_term:
preferred_term: molecular genetic testing
term:
id: NCIT:C19770
label: Molecular Analysis
qualifiers:
- predicate:
preferred_term: has participant
term:
id: RO:0000057
label: has participant
value:
preferred_term: USP7
term:
id: hgnc:12630
label: USP7
evidence:
- reference: PMID:35627274
reference_title: >-
Complex Presentation of Hao-Fountain Syndrome Solved by Exome Sequencing
Highlighting Co-Occurring Genomic Variants.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Here, we used whole-exome sequencing (WES) to solve an unclassified
multisystem clinical presentation.
explanation: This supports molecular genetic testing, specifically exome sequencing, as the diagnostic approach used to establish the syndrome.
differential_diagnoses: []
clinical_trials: []
datasets: []
notes: >-
Asta deep research was completed for this disorder. Final curation combined
the 2024 clinical spectrum paper with a disease-specific 2026 epigenetic and
transcriptomic study to support mechanistic pathophysiology. The expanded
cohort also reported abnormal pain thresholds, but that finding was not
promoted to a phenotype entry here because a confident best-fit HPO mapping
was not established in this pass.
Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.
Record notes
Asta deep research was completed for this disorder. Final curation combined the 2024 clinical spectrum paper with a disease-specific 2026 epigenetic and transcriptomic study to support mechanistic pathophysiology. The expanded cohort also reported abnormal pain thresholds, but that finding was not promoted to a phenotype entry here because a confident best-fit HPO mapping was not established in this pass.
This report is retrieval-only and is generated directly from Asta results.
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