Angioosteohypertrophic syndrome is a congenital vascular malformation and overgrowth disorder, often overlapping clinically with Klippel-Trenaunay syndrome. The disease is characterized by capillary-lymphatic-venous malformation of an extremity together with enlarged veins and segmental soft tissue or bony overgrowth. Many affected individuals harbor somatic mosaic activating PIK3CA mutations within affected tissue.
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Conditions with similar clinical presentations that must be differentiated from angioosteohypertrophic syndrome:
name: angioosteohypertrophic syndrome
creation_date: '2026-04-14T12:05:00Z'
updated_date: '2026-04-15T01:00:00Z'
category: Genetic
synonyms:
- Klippel-Trenaunay syndrome
- Klippel-Trenaunay-Weber syndrome
description: >-
Angioosteohypertrophic syndrome is a congenital vascular malformation and
overgrowth disorder, often overlapping clinically with Klippel-Trenaunay
syndrome. The disease is characterized by capillary-lymphatic-venous
malformation of an extremity together with enlarged veins and segmental soft
tissue or bony overgrowth. Many affected individuals harbor somatic mosaic
activating PIK3CA mutations within affected tissue.
disease_term:
preferred_term: angioosteohypertrophic syndrome
term:
id: MONDO:0007864
label: angioosteohypertrophic syndrome
parents:
- vascular malformation syndrome
- overgrowth syndrome
inheritance:
- name: Somatic mosaicism
description: >-
Many affected individuals have post-zygotic mosaic activating PIK3CA
variants confined to malformed tissue rather than a constitutional
inherited mutation.
evidence:
- reference: PMID:25681199
reference_title: Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Most individuals from Boston Children's Hospital who had isolated LM (16/17) or LM as part of a syndrome, such as KTS (19/21), fibro-adipose vascular anomaly (5/8), and congenital lipomatous overgrowth with vascular, epidermal, and skeletal anomalies syndrome (31/33) were somatic mosaic for PIK3CA mutations, with 5 specific PIK3CA mutations accounting for ∼ 80% of cases.
explanation: >-
This directly supports somatic mosaic PIK3CA activation as the main
genetic mechanism in Klippel-Trenaunay-spectrum vascular overgrowth.
pathophysiology:
- name: Somatic PIK3CA activation in malformed tissue
description: >-
Activating mosaic PIK3CA mutations arise in affected tissue and initiate the
vascular malformation and overgrowth phenotype.
genes:
- preferred_term: PIK3CA
term:
id: hgnc:8975
label: PIK3CA
evidence:
- reference: PMID:25681199
reference_title: Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Somatic PIK3CA mutations are the most common cause of isolated LMs and disorders in which LM is a component feature.
explanation: >-
This places somatic PIK3CA activation upstream of the vascular
malformation/overgrowth phenotype that includes KTS-spectrum disease.
downstream:
- target: Activated PI3K/mTOR signaling
description: Activated PIK3CA signaling drives pathological vascular growth.
- name: Activated PI3K/mTOR signaling
description: >-
Constitutive PIK3CA activation drives PI3K/mTOR pathway signaling in
malformed endothelial tissue.
cell_types:
- preferred_term: endothelial cell
term:
id: CL:0000115
label: endothelial cell
biological_processes:
- preferred_term: phosphatidylinositol-mediated signaling
term:
id: GO:0048015
label: phosphatidylinositol-mediated signaling
modifier: INCREASED
evidence:
- reference: DOI:10.1038/s41419-017-0064-x
reference_title: PI3K/mTOR inhibition promotes the regression of experimental vascular malformations driven by PIK3CA-activating mutations
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Our findings reveal that PIK3CA mutations have a key role in the
pathogenesis of VM and PIK3CA-driven experimental lesions can be
effectively treated by PI3K/mTOR inhibitors.
explanation: >-
This directly supports PI3K/mTOR pathway activation as the mechanistic
intermediate between PIK3CA mutation and vascular malformation.
downstream:
- target: Abnormal endothelial growth and sprouting
description: Activated PI3K/mTOR signaling promotes endothelial overgrowth and pathological sprouting.
- target: Segmental limb overgrowth
description: Mosaic PI3K pathway activation also promotes regional tissue overgrowth.
causal_link_type: DIRECT
- name: Abnormal endothelial growth and sprouting
description: >-
PIK3CA activation increases endothelial proliferation and angiogenic
behavior, promoting malformed vascular channels.
cell_types:
- preferred_term: endothelial cell
term:
id: CL:0000115
label: endothelial cell
biological_processes:
- preferred_term: angiogenesis
modifier: ABNORMAL
term:
id: GO:0001525
label: angiogenesis
evidence:
- reference: DOI:10.1038/s41419-017-0064-x
reference_title: PI3K/mTOR inhibition promotes the regression of experimental vascular malformations driven by PIK3CA-activating mutations
supports: SUPPORT
evidence_source: IN_VITRO
snippet: >-
Moreover, active forms of PIK3CA strongly promote the angiogenic sprouting.
explanation: >-
Human endothelial-cell experiments directly support pathological
angiogenic behavior downstream of activating PIK3CA mutations.
downstream:
- target: Capillary-venous malformation burden
description: Persistent endothelial dysregulation produces malformed superficial and venous vascular channels.
causal_link_type: DIRECT
- name: Capillary-venous malformation burden
description: >-
Persistent endothelial dysregulation produces the capillary and venous
malformation burden that defines the vascular component of the syndrome.
evidence:
- reference: PMID:25681199
reference_title: Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
KTS has been recognized for more than a century 23; we defined the
condition as comprised of overgrowth, cutaneous capillary and lymphatic
malformation, and persistence of embryonic vasculature in an extremity
12, 14.
explanation: >-
This directly supports the vascular-malformation endpoint of
Klippel-Trenaunay-spectrum disease.
downstream:
- target: Nevus flammeus
description: Capillary malformation burden is expressed clinically as nevus flammeus.
causal_link_type: DIRECT
- target: Varicose veins
description: Venous malformation burden is expressed clinically as varicose veins.
causal_link_type: DIRECT
- target: Localized pain
description: Extensive vascular malformations contribute to localized pain.
causal_link_type: DIRECT
- name: Segmental limb overgrowth
description: >-
Mosaic PIK3CA activation also drives regional soft-tissue and bony
enlargement of the affected extremity.
evidence:
- reference: PMID:25788406
reference_title: Surgical treatment of varicose veins and venous malformations in Klippel-Trenaunay syndrome.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
All had varicose veins, 36 (73%) had limb hypertrophy, and 33 (67%) had capillary malformations, with two of three clinical features present in all.
explanation: >-
This directly supports segmental limb overgrowth as a parallel major
disease outcome in Klippel-Trenaunay-spectrum disease.
downstream:
- target: Limb hypertrophy
description: Regional overgrowth is expressed clinically as limb hypertrophy.
causal_link_type: DIRECT
phenotypes:
- name: Nevus flammeus
category: Skin
frequency: FREQUENT
description: >-
Cutaneous capillary malformation is one of the characteristic surface
markers of the syndrome.
phenotype_term:
preferred_term: Port-wine stain
term:
id: HP:0001052
label: Nevus flammeus
evidence:
- reference: PMID:25788406
reference_title: Surgical treatment of varicose veins and venous malformations in Klippel-Trenaunay syndrome.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
All had varicose veins, 36 (73%) had limb hypertrophy, and 33 (67%) had capillary malformations, with two of three clinical features present in all.
explanation: >-
This cohort shows that capillary malformation is one of the defining
major features of Klippel-Trenaunay-spectrum disease.
- name: Limb hypertrophy
category: Musculoskeletal
frequency: FREQUENT
description: >-
Segmental overgrowth involving soft tissue and bone commonly affects the
involved limb.
phenotype_term:
preferred_term: Limb hypertrophy
term:
id: HP:0001548
label: Overgrowth
evidence:
- reference: PMID:25788406
reference_title: Surgical treatment of varicose veins and venous malformations in Klippel-Trenaunay syndrome.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
All had varicose veins, 36 (73%) had limb hypertrophy, and 33 (67%) had capillary malformations, with two of three clinical features present in all.
explanation: >-
This directly documents limb hypertrophy as a frequent component of the
clinical triad.
- name: Localized pain
category: Musculoskeletal
frequency: VERY_FREQUENT
description: >-
Pain is a common symptomatic consequence of the extensive venous and
vascular malformation burden.
phenotype_term:
preferred_term: Pain
term:
id: HP:0012531
label: Pain
evidence:
- reference: PMID:25788406
reference_title: Surgical treatment of varicose veins and venous malformations in Klippel-Trenaunay syndrome.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The most frequent symptom was pain (N = 43, 88%).
explanation: >-
This directly supports pain as a common clinical manifestation.
- name: Varicose veins
category: Cardiovascular
frequency: VERY_FREQUENT
description: >-
Enlarged superficial veins are a defining feature of the syndrome and part
of the classic Klippel-Trenaunay triad.
phenotype_term:
preferred_term: Varicose veins
term:
id: HP:0002619
label: Varicose veins
evidence:
- reference: PMID:25788406
reference_title: Surgical treatment of varicose veins and venous malformations in Klippel-Trenaunay syndrome.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
All had varicose veins, 36 (73%) had limb hypertrophy, and 33 (67%) had
capillary malformations, with two of three clinical features present in
all.
explanation: >-
This directly supports varicose veins as an obligate or near-obligate
defining phenotype in the reported Klippel-Trenaunay cohort.
biochemical: []
genetic:
- name: PIK3CA
association: Somatic activating mutation
gene_term:
preferred_term: PIK3CA
term:
id: hgnc:8975
label: PIK3CA
notes: >-
Angioosteohypertrophic/Klippel-Trenaunay-spectrum disease is frequently
part of the PIK3CA-related overgrowth spectrum.
evidence:
- reference: PMID:25681199
reference_title: Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Somatic PIK3CA mutations are the most common cause of isolated LMs and disorders in which LM is a component feature.
explanation: >-
This directly supports PIK3CA as the recurrent causal gene in
Klippel-Trenaunay-spectrum vascular overgrowth.
environmental: []
treatments:
- name: Surgical treatment of symptomatic venous malformations
treatment_term:
preferred_term: surgical procedure
term:
id: MAXO:0000004
label: surgical procedure
description: >-
Selected patients with disabling venous symptoms may benefit from operative
treatment of varicose veins and venous malformations.
evidence:
- reference: PMID:25788406
reference_title: Surgical treatment of varicose veins and venous malformations in Klippel-Trenaunay syndrome.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In selected symptomatic patients with KT syndrome, open surgical treatment is safe and durable.
explanation: >-
This supports surgery as a treatment option for symptomatic
Klippel-Trenaunay-spectrum disease.
- name: PI3K/mTOR inhibitor pharmacotherapy
treatment_term:
preferred_term: Pharmacotherapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: everolimus
term:
id: CHEBI:68478
label: everolimus
description: >-
PI3K/mTOR-pathway inhibition can reduce experimental vascular malformation
burden in PIK3CA-driven disease.
evidence:
- reference: DOI:10.1038/s41419-017-0064-x
reference_title: PI3K/mTOR inhibition promotes the regression of experimental vascular malformations driven by PIK3CA-activating mutations
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Such vascular lesions are ameliorated by administration of dual
PI3K/mTOR inhibitor, BEZ235, and mTOR inhibitor, Everolimus.
explanation: >-
This directly supports mTOR-pathway pharmacotherapy as a mechanistically
targeted treatment strategy in PIK3CA-driven vascular malformations.
diagnosis:
- name: Clinical assessment
diagnosis_term:
preferred_term: clinical assessment
term:
id: MAXO:0000487
label: clinical assessment
description: >-
Diagnosis is based on the combination of vascular malformation, enlarged
veins, and regional overgrowth.
results: Capillary-lymphatic malformation with enlarged veins and limb overgrowth supports the diagnosis.
- name: Affected-tissue genetic testing
diagnosis_term:
preferred_term: genetic testing
term:
id: MAXO:0000127
label: genetic testing
description: >-
Sequencing of affected tissue can identify low-level somatic mosaic PIK3CA
variants.
results: Somatic mosaic PIK3CA mutation in affected tissue supports the diagnosis.
differential_diagnoses:
- name: CLOVES syndrome
disease_term:
preferred_term: CLOVES syndrome
term:
id: MONDO:0013038
label: CLOVES syndrome
description: >-
CLOVES syndrome is another PIK3CA-related overgrowth disorder with vascular
malformations but broader truncal adipose and skeletal involvement.
evidence:
- reference: PMID:25681199
reference_title: Lymphatic and other vascular malformative/overgrowth disorders are caused by somatic mutations in PIK3CA.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Individuals with malformative syndromes resulting from somatic PIK3CA mutations have a spectrum of phenotypes, often non-overlapping (e.g., hemimegalencaphy versus macrodactyly) 4–9. Lymphatic malformations (LM), which arise most frequently as an isolated vascular anomaly, are a major component feature in patients that have CLOVES syndrome 11 and Klippel-Trenaunay syndrome (KTS) 12.
explanation: >-
This explicitly links CLOVES and KTS as overlapping PIK3CA-related
vascular overgrowth disorders and supports CLOVES syndrome as a key
differential diagnosis.
clinical_trials: []
datasets: []
This report is retrieval-only and is generated directly from Asta results.
search_papers_by_relevance with snippet_search.