Pacak-Zhuang syndrome is an ultra-rare mosaic tumor-predisposition syndrome caused by early postzygotic gain-of-function mutations in EPAS1, which encodes HIF-2alpha. The core phenotype is childhood-onset polycythemia followed by pheochromocytoma/paraganglioma-spectrum tumors and somatostatinoma, with additional reported ophthalmologic abnormalities and vascular/cystic lesions. Mechanistically, disease-causing EPAS1 variants stabilize HIF-2alpha, impair oxygen-dependent degradation, and drive constitutive hypoxia-pathway activation with persistent erythropoietin signaling and neuroendocrine tumor predisposition.
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name: Pacak-Zhuang syndrome
creation_date: '2026-04-16T19:19:03Z'
updated_date: '2026-04-20T03:02:00Z'
category: Genetic
description: >-
Pacak-Zhuang syndrome is an ultra-rare mosaic tumor-predisposition syndrome
caused by early postzygotic gain-of-function mutations in EPAS1, which encodes
HIF-2alpha. The core phenotype is childhood-onset polycythemia followed by
pheochromocytoma/paraganglioma-spectrum tumors and somatostatinoma, with
additional reported ophthalmologic abnormalities and vascular/cystic lesions.
Mechanistically, disease-causing EPAS1 variants stabilize HIF-2alpha, impair
oxygen-dependent degradation, and drive constitutive hypoxia-pathway
activation with persistent erythropoietin signaling and neuroendocrine tumor
predisposition.
parents:
- pheochromocytoma-paraganglioma
synonyms:
- EPAS1 gain-of-function mutation syndrome
- polycythemia-paraganglioma-somatostatinoma syndrome
disease_term:
preferred_term: Pacak-Zhuang syndrome
term:
id: MONDO:0035540
label: pheochromocytoma-paraganglioma
mappings:
mondo_mappings:
- term:
id: MONDO:0035540
label: pheochromocytoma-paraganglioma
mapping_predicate: skos:closeMatch
mapping_source: MONDO
mapping_justification: >-
MONDO new term request 9960 requests a dedicated Pacak-Zhuang syndrome
term; until that
term is merged, pheochromocytoma-paraganglioma is the closest available
MONDO disease anchor for the syndrome's core neuroendocrine tumor
component.
inheritance:
- name: Somatic Mosaicism
description: >-
Pacak-Zhuang syndrome is caused by early postzygotic somatic gain-of-function
mutations in EPAS1 rather than inherited germline variation. Mosaic
distribution across tissues explains variable organ involvement and the
non-Mendelian recurrence pattern.
evidence:
- reference: PMID:37450881
reference_title: "Pacak-Zhuang syndrome: a model providing new insights into tumor syndromes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Herein, we review our initial identification of a new syndrome of multiple
paragangliomas, somatostatinomas, and polycythemia caused by early
postzygotic mosaic mutations in EPAS1, encoding hypoxia-inducible factor 2
alpha (HIF-2α)
explanation: >-
Review article explicitly defines the syndrome as an early postzygotic
mosaic EPAS1 disorder.
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Six females and one male presented at a median age of 28 years (range
11-46). Two were found to have HIF2A somatic mosaicism. No relatives were
affected.
explanation: >-
Clinical series supports somatic mosaic, non-familial disease causation.
prevalence:
- population: Worldwide reported literature
percentage: Unknown
notes: >-
Population prevalence has not been established. The syndrome remains known
mainly from small case series and individual reports.
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
are described in only a few patients with somatic mutations in the
hypoxia-inducible factor 2 alpha (HIF2A).
explanation: >-
This cohort paper explicitly describes the syndrome as being limited to
only a few reported patients.
pathophysiology:
- name: Somatic mosaic EPAS1 activation
description: >-
Early postzygotic gain-of-function mutations in EPAS1 create mosaic cell
populations with constitutive HIF-2alpha activity.
genes:
- preferred_term: EPAS1
term:
id: hgnc:3374
label: EPAS1
evidence:
- reference: PMID:37450881
reference_title: "Pacak-Zhuang syndrome: a model providing new insights into tumor syndromes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Herein, we review our initial identification of a new syndrome of multiple
paragangliomas, somatostatinomas, and polycythemia caused by early
postzygotic mosaic mutations in EPAS1
explanation: >-
Supports EPAS1 as the causal gene and places the mutational event early in
embryonic development.
- reference: PMID:23509317
reference_title: "New syndrome of paraganglioma and somatostatinoma associated with polycythemia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Patients were found to have polycythemia, multiple PGLs, and duodenal
somatostatinomas by imaging or biochemistry with somatic gain-of-function
HIF2A mutations.
explanation: >-
Landmark case series identifies activating somatic HIF2A/EPAS1 mutations in
affected patients.
downstream:
- target: Impaired HIF-2alpha hydroxylation and degradation
description: >-
Disease-associated variants interfere with the normal oxygen-sensing
degradation machinery.
- name: Impaired HIF-2alpha hydroxylation and degradation
description: >-
Syndrome-associated HIF2A variants cluster near the oxygen-sensing proline
residue, decrease prolyl hydroxylation, reduce VHL binding, and prolong
HIF-2alpha half-life under normoxic conditions.
biological_processes:
- preferred_term: response to hypoxia
modifier: INCREASED
term:
id: GO:0001666
label: response to hypoxia
evidence:
- reference: PMID:23509317
reference_title: "New syndrome of paraganglioma and somatostatinoma associated with polycythemia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The HIF2A mutations in these patients were clustered adjacent to an
oxygen-sensing proline residue, affecting HIF2α interaction with the
prolyl hydroxylase domain 2-containing protein, decreasing the
hydroxylation of HIF2α, and reducing HIF2α affinity for the von
Hippel-Lindau protein and its degradation.
explanation: >-
Directly supports the protein-stabilization mechanism that activates the
HIF pathway in this syndrome.
downstream:
- target: Hypoxia-response gene upregulation
description: Stabilized HIF-2alpha increases transcription of HIF target genes.
- name: Hypoxia-response gene upregulation
description: >-
Stabilized HIF-2alpha upregulates hypoxia-response genes including EPO,
VEGFA, GLUT1, and END1, producing persistent erythrocytosis signals and a
pseudohypoxic tumor program.
biological_processes:
- preferred_term: cellular response to hypoxia
modifier: INCREASED
term:
id: GO:0071456
label: cellular response to hypoxia
evidence:
- reference: PMID:23509317
reference_title: "New syndrome of paraganglioma and somatostatinoma associated with polycythemia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
An increase in the half-life of HIF2α was associated with upregulation
of the hypoxia-related genes EPO, VEGFA, GLUT1, and END1 in tumors.
explanation: >-
Direct evidence that stabilized HIF-2alpha increases transcription of
canonical hypoxia-response genes in syndrome-associated tumors.
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Polycythemia was detected in patients in early childhood (median 2 years,
range from birth to 7 years). Erythropoietin (EPO) levels were an average
of 5 times above the upper limit of normal in all patients.
explanation: >-
Supports downstream physiological activation of the erythropoietin axis in
affected patients.
downstream:
- target: Neuroendocrine tumor predisposition
description: Pseudohypoxic signaling predisposes to PPGL-spectrum tumors and somatostatinoma.
- name: Neuroendocrine tumor predisposition
description: >-
HIF-2alpha pathway activation predisposes chromaffin and enteroendocrine
lineages to recurrent multifocal neuroendocrine tumors within the
pheochromocytoma/paraganglioma and somatostatinoma spectrum.
cell_types:
- preferred_term: chromaffin cell
term:
id: CL:0000166
label: chromaffin cell
- preferred_term: type D enteroendocrine cell
term:
id: CL:0000502
label: type D enteroendocrine cell
evidence:
- reference: PMID:23509317
reference_title: "New syndrome of paraganglioma and somatostatinoma associated with polycythemia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Patients were found to have polycythemia, multiple PGLs, and duodenal
somatostatinomas by imaging or biochemistry with somatic gain-of-function
HIF2A mutations.
explanation: >-
Establishes the core neuroendocrine tumor phenotype linked to EPAS1/HIF2A
activation.
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
PGLs were found at a median age of 17 years (range 8-38) and SOMs at 29
years (range 22-38). PGLs were multiple, recurrent and metastatic in 100,
100 and 29% of all cases, and SOMs in 40, 40 and 60%, respectively.
explanation: >-
Documents the characteristic recurrent multifocal PPGL/somatostatinoma
tumor spectrum in the syndrome.
phenotypes:
- category: Hematologic
name: Polycythemia
frequency: VERY_FREQUENT
diagnostic: true
description: >-
Polycythemia typically presents at birth or in early childhood and usually
precedes tumor detection by years.
phenotype_term:
preferred_term: Polycythemia
term:
id: HP:0001901
label: Polycythemia
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: All patients were diagnosed with polycythemia before age 8
explanation: >-
This clinical series supports early childhood polycythemia as a hallmark
presenting feature.
- category: Neoplastic
name: Paraganglioma
frequency: VERY_FREQUENT
diagnostic: true
description: >-
Paragangliomas are the dominant PPGL-spectrum tumor manifestation in
Pacak-Zhuang syndrome and are often multifocal, recurrent, and
norepinephrine-producing.
phenotype_term:
preferred_term: Paraganglioma
term:
id: HP:0002668
label: Paraganglioma
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
PGL developed later in life at a median age of 17 years (range 8–38) in
all patients. PGLs were predominantly of the norepinephrine-producing
biochemical phenotype.
explanation: >-
Supports paraganglioma as the universal and dominant PPGL-spectrum tumor
manifestation in the cohort.
- category: Neoplastic
name: Pheochromocytoma
frequency: FREQUENT
description: >-
Adrenal involvement occurs in a substantial subset of patients, indicating a
frequent pheochromocytoma component within the broader PPGL phenotype.
phenotype_term:
preferred_term: Pheochromocytoma
term:
id: HP:0002666
label: Pheochromocytoma
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Patients were found to have multiple (100%), recurrent (100%), and
metastatic (29%) PGLs, with adrenal involvement in four cases.
explanation: >-
Adrenal involvement in four of seven patients supports a frequent
pheochromocytoma component.
- category: Neoplastic
name: Somatostatinoma
frequency: FREQUENT
diagnostic: true
description: >-
Somatostatinomas are usually duodenal, tend to appear after the PPGL
phenotype, and may recur or metastasize despite young age of onset.
phenotype_term:
preferred_term: somatostatinoma
term:
id: HP:0100634
label: Neuroendocrine neoplasm
evidence:
- reference: PMID:23509317
reference_title: "New syndrome of paraganglioma and somatostatinoma associated with polycythemia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Patients were found to have polycythemia, multiple PGLs, and duodenal
somatostatinomas by imaging or biochemistry with somatic gain-of-function
HIF2A mutations.
explanation: >-
Original syndrome report establishes duodenal somatostatinoma as part of
the defining clinical triad.
- category: Ophthalmologic
name: Ophthalmologic abnormalities
frequency: VERY_FREQUENT
description: >-
Eye findings are common and include optic disc fibrosis with additional
retinal or macular changes in some patients.
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
We observed optic disc fibrosis in all patients (Supplementary Figure 1).
explanation: >-
Supports ophthalmologic involvement as a near-constant associated feature.
- category: Vascular
name: Vascular malformations and cystic lesions
frequency: FREQUENT
description: >-
Associated lesions include hemangiomas and cysts in multiple organs, and
later reports expanded the syndrome spectrum to developmental vascular
malformations.
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Computed tomography (CT) and magnetic resonance imaging revealed cystic
lesions at multiple sites and hemangiomas in 4 patients (57%)
explanation: >-
Cohort study documents frequent associated cystic and hemangiomatous
lesions.
- reference: PMID:37450881
reference_title: "Pacak-Zhuang syndrome: a model providing new insights into tumor syndromes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
our continued exploration of new disease phenotypes in this syndrome,
including vascular malformations and neural tube defects.
explanation: >-
Review broadens the recognized phenotype to include developmental vascular
malformations.
- category: Developmental
name: Neural tube defects
frequency: OCCASIONAL
description: >-
Neural tube defects have been reported as an expanded developmental
phenotype in Pacak-Zhuang syndrome, consistent with the early embryonic
timing of the mosaic EPAS1 defect.
phenotype_term:
preferred_term: Neural tube defect
term:
id: HP:0045005
label: Neural tube defect
evidence:
- reference: PMID:37450881
reference_title: "Pacak-Zhuang syndrome: a model providing new insights into tumor syndromes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
our continued exploration of new disease phenotypes in this syndrome,
including vascular malformations and neural tube defects.
explanation: >-
Review identifies neural tube defects as an expanded but not yet
frequency-quantified syndrome phenotype.
- category: Gastrointestinal
name: Gallbladder disease
frequency: FREQUENT
description: >-
Gallbladder disease is a frequent associated manifestation, particularly in
patients with somatostatinoma, and includes chronic cholecystitis and
cholelithiasis.
phenotype_term:
preferred_term: Abnormality of the gallbladder
term:
id: HP:0005264
label: Abnormality of the gallbladder
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
gallbladder disease, with four having chronic cholecystitis and two,
cholelithiasis, usually in early adulthood at a median of 29 years (range
19–39).
explanation: >-
Cohort study supports frequent gallbladder involvement and specifies the
dominant manifestations as cholecystitis and cholelithiasis.
biochemical:
- name: Erythropoietin
notes: >-
Erythropoietin levels are often markedly elevated from early life and may
remain abnormal after tumor resection, supporting systemic mosaic HIF
pathway activation rather than purely paraneoplastic secretion.
- name: Plasma or urine metanephrines
notes: >-
Annual catecholamine metabolite surveillance is recommended because the
PPGL phenotype is usually norepinephrine-predominant and recurrent.
- name: Somatostatin
notes: >-
Plasma somatostatin levels can support detection and follow-up of
somatostatinoma, particularly in adults who have already developed PPGL.
diagnosis:
- name: Whole-body imaging surveillance
diagnosis_term:
preferred_term: clinical assessment
term:
id: MAXO:0000487
label: clinical assessment
description: >-
Regular whole-body or abdominal imaging surveillance is recommended to
localize recurrent or multifocal PPGL-spectrum tumors, with MRI preferred
in children.
results: Detection of recurrent or newly localized PPGL-spectrum lesions supports surveillance and management.
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
perform regular (every 1–2 years) whole body or at least abdominal
imaging, MRI in children;
explanation: >-
This directly supports regular imaging surveillance as part of diagnosis
and longitudinal follow-up in Pacak-Zhuang syndrome.
- name: FDOPA PET/CT for PPGL localization
diagnosis_term:
preferred_term: positron emission tomography and computed tomography scan
term:
id: NCIT:C103512
label: Positron Emission Tomography and Computed Tomography Scan
description: >-
For the pheochromocytoma/paraganglioma component of Pacak-Zhuang syndrome,
FDOPA PET/CT is a high-yield localization study that can complement
syndrome surveillance imaging.
results: Improved localization of PCC/PGL lesions supports staging and management.
evidence:
- reference: DOI:10.1186/s13550-023-01056-4
reference_title: "[18F]FDOPA PET/CT is superior to [68Ga]DOTATOC PET/CT in diagnostic imaging of pheochromocytoma"
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
FDOPA is superior to DOTATOC for localization of PCC. In contrast to
DOTATOC, FDOPA also identified all PGL but with a limited number of
patient cases.
explanation: >-
This directly supports FDOPA PET/CT as a strong localization study for
the PCC/PGL tumor spectrum that defines the neuroendocrine component of
Pacak-Zhuang syndrome.
- name: EPAS1/HIF2A mutation testing
diagnosis_term:
preferred_term: molecular genetic testing
term:
id: MAXO:0000127
label: genetic testing
description: >-
Molecular testing for EPAS1/HIF2A should be considered in patients with
congenital polycythemia or the characteristic tumor spectrum.
results: Identification of a pathogenic mosaic EPAS1/HIF2A variant supports diagnosis.
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: consider genetic testing for HIF2A mutations in congenital polycythemia;
explanation: >-
The cohort paper explicitly recommends HIF2A testing in the relevant
clinical setting.
genetic:
- name: EPAS1
association: Early postzygotic somatic mosaic gain-of-function mutation
gene_term:
preferred_term: EPAS1
term:
id: hgnc:3374
label: EPAS1
notes: >-
EPAS1 encodes HIF-2alpha. Reported pathogenic variants affect the
oxygen-sensing degradation region of HIF-2alpha, impair PHD/VHL-mediated
turnover, and stabilize the transcription factor. Variants are typically
somatic and mosaic rather than inherited through the germline.
evidence:
- reference: PMID:23509317
reference_title: "New syndrome of paraganglioma and somatostatinoma associated with polycythemia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Each patient carried an identical unique mutation in both types of tumors
but not in germline DNA.
explanation: >-
Establishes that the causal HIF2A/EPAS1 variants are somatic rather than
germline.
- reference: PMID:37450881
reference_title: "Pacak-Zhuang syndrome: a model providing new insights into tumor syndromes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Herein, we review our initial identification of a new syndrome of multiple
paragangliomas, somatostatinomas, and polycythemia caused by early
postzygotic mosaic mutations in EPAS1
explanation: >-
Confirms EPAS1 as the established syndrome gene and frames the mosaic
developmental timing as clinically important.
treatments:
- name: Surgical management
description: >-
Surgery remains the main treatment for localized PPGL and somatostatinoma
lesions, but repeated interventions are often required because tumors are
multifocal and recurrent.
treatment_term:
preferred_term: surgical procedure
term:
id: MAXO:0000004
label: surgical procedure
evidence:
- reference: PMID:27679736
reference_title: "Novel insights into the polycythemia-paraganglioma-somatostatinoma syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: Current treatment options are exclusively surgical.
explanation: >-
Cohort follow-up describes surgery as the historical standard of care.
- name: Belzutifan
description: >-
Selective HIF-2alpha inhibition with belzutifan has produced a rapid and
sustained response in an EPAS1-mosaic patient, improving tumor burden,
hypertension, headaches, and long-standing polycythemia.
treatment_term:
preferred_term: Pharmacotherapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: belzutifan
term:
id: NCIT:C135627
label: Belzutifan
evidence:
- reference: PMID:34818480
reference_title: "Belzutifan, a Potent HIF2alpha Inhibitor, in the Pacak-Zhuang Syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Treatment with belzutifan led to a rapid and sustained tumor response
along with resolution of hypertension, headaches, and long-standing
polycythemia.
explanation: >-
Case report provides direct proof-of-mechanism that HIF-2alpha inhibition
can reverse core disease manifestations.
This report is retrieval-only and is generated directly from Asta results.
search_papers_by_relevance with snippet_search.