PAPA Syndrome

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Inheritance

1

Autosomal dominant inheritance HP:0000006

PAPA syndrome is inherited in an autosomal dominant manner from heterozygous PSTPIP1 missense variants, with incomplete penetrance and markedly variable expressivity documented both between and within families. Each child of an affected individual has a 50% risk of inheriting the variant.

Autosomal dominant inheritance

Show evidence (2 references)

PMID:21532836 SUPPORT Other

"PAPA syndrome (Pyogenic Arthritis, Pyoderma gangrenosum, and Acne) is an autosomal dominant, hereditary auto-inflammatory disease arising from mutations in the PSTPIP1/CD2BP1 gene on chromosome 15q."

The review states PAPA syndrome is autosomal dominant and arises from PSTPIP1/CD2BP1 mutations on chromosome 15q.

PMID:22161697 SUPPORT Human Clinical

"This analysis of 5 patients demonstrates that mutations in PSTPIP1 are incompletely penetrant and variably expressed in the PAPA syndrome."

Documents incomplete penetrance and variable expressivity of PSTPIP1 variants in PAPA syndrome.

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Discussions and Knowledge Gaps

1

Why does the PSTPIP1 A230T mouse reproduce systemic cytokine elevation but not the joint and skin lesions that define human PAPA syndrome?

HUMAN MODEL MISMATCH OPEN papa_a230t_mouse_model_mismatch

Attached to

pathophysiology#Neutrophilic Sterile Inflammation

The A230T mouse recapitulates the inflammasome/cytokine arm (elevated circulating proinflammatory cytokines) yet fails to develop pyogenic arthritis or skin inflammation, so the causal step from IL-1-driven systemic inflammation to organ-specific neutrophilic tissue lesions is not established in vivo and may depend on species- or context-specific factors absent from the model.

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Pathophysiology

6

Loss of PSTPIP1-PTP-PEST Binding

PAPA-associated missense variants (p.A230T, p.E250Q) in the coiled-coil domain of PSTPIP1 severely reduce binding to the regulatory phosphatase PTP-PEST, releasing PSTPIP1 from dephosphorylation so that mutant protein accumulates in a hyperphosphorylated state. This loss of phosphatase engagement is the initiating molecular lesion; the resulting gain of function (enhanced pyrin binding) is modeled as the downstream node.

PSTPIP1 hgnc:9580

PTP-PEST (protein phosphatase) binding GO:0019903 ↓ DECREASED

Downstream

Enhanced PSTPIP1-Pyrin Binding

Show evidence (1 reference)

PMID:11971877 SUPPORT In Vitro

"Yeast two-hybrid assays demonstrate severely reduced binding between PTP PEST and both the E250Q and A230T mutant proteins."

The causal variants abolish PTP-PEST binding, the initiating molecular lesion.

Enhanced PSTPIP1-Pyrin Binding

Hyperphosphorylated mutant PSTPIP1 binds pyrin (the MEFV gene product) with markedly increased avidity, mechanistically placing PAPA syndrome in the same pyrin pathway as familial Mediterranean fever.

Downstream

Pyrin Inflammasome Assembly

Show evidence (2 references)

PMID:14595024 SUPPORT In Vitro

"Endogenous PSTPIP1/CD2BP1 and pyrin are coexpressed in monocytes and granulocytes and can be coimmunoprecipitated from THP-1 cells."

Demonstrates the physical PSTPIP1-pyrin interaction that the PAPA mutations amplify.

PMID:19584923 SUPPORT In Vitro

"Since disease-associated mutations in PSTPIP1 enhance pyrin binding, PAPA syndrome and FMF are thought to share a common pathoetiology."

States that PAPA-associated PSTPIP1 mutations enhance pyrin binding.

Pyrin Inflammasome Assembly

Increased pyrin engagement drives assembly of the pyrin inflammasome (ASC specks) and caspase-1 activation, escaping the normal PTP-PEST/pyrin autoinhibitory checkpoint.

monocyte CL:0000576 neutrophil CL:0000775

pyrin inflammasome complex assembly GO:0140632 ⇑ GAIN OF FUNCTION

Downstream

Excess IL-1beta Production

Show evidence (1 reference)

PMID:19584923 SUPPORT In Vitro

"PSTPIP1 molecules with PAPA-associated mutations are recruited by pyrin to ASC specks with particularly high efficiency, suggesting a unique mechanism underlying the robust inflammatory phenotype of PAPA syndrome."

Direct evidence for enhanced pyrin-inflammasome (ASC speck) assembly by PAPA-mutant PSTPIP1.

Excess IL-1beta Production

Pyrin-inflammasome activation cleaves pro-IL-1beta via caspase-1, producing IL-1beta overproduction that is a defining molecular feature of PAPA syndrome and is measurable as markedly elevated IL-1beta in patients.

monocyte CL:0000576 neutrophil CL:0000775 macrophage CL:0000235

interleukin-1 beta production GO:0032611 ↑ INCREASED

Animal models

PSTPIP1 A230T ectopic-expression mouse Mouse partially recapitulates Mutant PSTPIP1 expression elevates circulating proinflammatory cytokines, recapitulating the systemic cytokine arm of PAPA.

Downstream

Neutrophilic Sterile Inflammation

Elevated CRP

Show evidence (3 references)

PMID:21532836 SUPPORT Other

"Overproduction of IL-1β is a clear molecular feature of PAPA syndrome."

States IL-1beta overproduction as a defining molecular feature of PAPA syndrome.

PMID:22161697 SUPPORT Human Clinical

"Interleukin-1β (IL-1β) and circulating neutrophil granule enzyme levels were markedly elevated in patients compared to those in controls."

Measures markedly elevated IL-1beta in PAPA patients versus controls.

PMID:14595024 SUPPORT In Vitro

"we found increased IL-1beta production by peripheral blood leukocytes from a clinically active PAPA patient with the A230T PSTPIP1/CD2BP1 mutation and in cell lines transfected with both PAPA-associated mutants."

Demonstrates increased IL-1beta production in cells from a PAPA patient and in mutant-transfected cell lines.

Neutrophilic Sterile Inflammation

IL-1-driven recruitment of neutrophils produces sterile, neutrophil-rich (pyogenic) inflammation of joints and skin; recurring episodes accumulate sterile pyogenic material in affected joints, ultimately causing destruction, and drive the cutaneous lesions.

neutrophil CL:0000775

production of molecular mediator involved in inflammatory response GO:0002532 ↑ INCREASED

Downstream

Sterile pyogenic arthritis

Progressive joint destruction

Pyoderma gangrenosum

Cystic acne

Positive pathergy test

Show evidence (1 reference)

PMID:11971877 SUPPORT Human Clinical

"Recurring inflammatory episodes lead to accumulation of sterile, pyogenic, neutrophil-rich material within the affected joints, ultimately resulting in significant destruction."

Describes the sterile neutrophil-rich joint inflammation and resulting destruction.

PSTPIP1 Cytoskeletal Adaptor Dysregulation

Beyond the inflammasome arm, PSTPIP1 is an F-BAR/SH3 cytoskeletal adaptor that links CD2 to WASP-driven actin polymerization at the immunological synapse and regulates myeloid-cell migration. Perturbation of this cytoskeletal-regulatory function is proposed to contribute to the exaggerated neutrophil influx at sites of minor trauma (pathergy); the link to pathergy is inferential rather than demonstrated.

T cell CL:0000084 neutrophil CL:0000775

actin filament organization GO:0007015

Downstream

Neutrophilic Sterile Inflammation

Show evidence (1 reference)

PMID:12530983 SUPPORT INDIRECT In Vitro

"PSTPIP1 acts downstream of CD2/CD2AP to link CD2 engagement to the WASp-evoked actin polymerization required for synapse formation and T cell activation."

Establishes PSTPIP1's cytoskeletal adaptor role; its contribution to pathergy in PAPA is an inference from this normal function.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

6

Immune 1

Cystic acne FREQUENT HP:0033188

Show evidence (1 reference)

PMID:22161697 SUPPORT Human Clinical

"Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"

Lists severe cystic acne among the cutaneous manifestations.

Integument 2

Pyoderma gangrenosum FREQUENT HP:0025452

Show evidence (1 reference)

PMID:22161697 SUPPORT Human Clinical

"Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"

Lists pyoderma gangrenosum (recurrent nonhealing sterile ulcers) among the cutaneous manifestations.

Positive pathergy test FREQUENT HP:0025532

Show evidence (1 reference)

PMID:22161697 SUPPORT Human Clinical

"Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"

Names pathergy (abscesses at injection sites) as a cutaneous manifestation.

Metabolism 1

Elevated CRP FREQUENT Elevated circulating C-reactive protein concentration HP:0011227

Temporal: ACUTE

Show evidence (1 reference)

PMID:22161697 SUPPORT DIRECT Human Clinical

"Levels of the acute-phase reactants C-reactive protein (CRP) and lipopolysaccharide binding protein and of the enzyme matrix metalloproteinase 9 were also significantly elevated compared to those in controls (Figure 2)."

Measures significantly elevated CRP (an acute-phase reactant) in PAPA patients compared with controls.

Musculoskeletal 2

Sterile pyogenic arthritis VERY_FREQUENT Sterile arthritis HP:0040310

Temporal: RECURRENT

Show evidence (2 references)

PMID:22161697 SUPPORT Human Clinical

"PAPA syndrome typically presents with recurrent sterile, erosive arthritis in childhood, occurring spontaneously or after minor trauma, occasionally resulting in significant joint destruction. By puberty, joint symptoms tend to subside and cutaneous symptoms increase."

Describes the childhood-onset recurrent sterile erosive arthritis and its temporal course.

PMID:28251506 SUPPORT Human Clinical

"Pyogenic arthritis, pyoderma gangrenosum and acne syndrome was diagnosed in a 42-year-old patient, after an unusual persistency of high synovial cell counts had been noticed."

Documents the persistently high sterile synovial cell counts characteristic of the arthritis.

Progressive joint destruction OCCASIONAL HP:0005187

Show evidence (2 references)

PMID:11971877 SUPPORT Human Clinical

"Recurring inflammatory episodes lead to accumulation of sterile, pyogenic, neutrophil-rich material within the affected joints, ultimately resulting in significant destruction."

Recurrent sterile joint inflammation ultimately produces significant joint destruction.

PMID:22161697 SUPPORT Human Clinical

"recurrent sterile, erosive arthritis in childhood, occurring spontaneously or after minor trauma, occasionally resulting in significant joint destruction"

States that significant joint destruction results only occasionally, supporting the OCCASIONAL frequency.

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Genetic Associations

1

PSTPIP1 (Causative)

Gene: PSTPIP1 hgnc:9580 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:11971877 SUPPORT In Vitro

"E250Q or A230T amino acid substitutions occur within a domain highly homologous to yeast cleavage furrow-associated protein CDC15."

Identifies the two co-segregating PAPA-causing PSTPIP1/CD2BP1 missense substitutions in the coiled-coil domain.

PMID:11971877 SUPPORT In Vitro

"Yeast two-hybrid assays demonstrate severely reduced binding between PTP PEST and both the E250Q and A230T mutant proteins."

Establishes the functional consequence of the causal variants - loss of PTP-PEST binding.

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Medical Actions

4

IL-1 blockade (anakinra, canakinumab)

Action: Pharmacotherapy NCIT:C15986

Agent: anakinra NCIT:C38717 canakinumab NCIT:C80971

Platform: Other

Interleukin-1 blockade is the mainstay biologic strategy, targeting the IL-1beta-driven mechanism and most effective for the arthritis component. The recombinant IL-1 receptor antagonist anakinra and the anti-IL-1beta monoclonal antibody canakinumab are both used; the cutaneous manifestations (particularly cystic acne) respond less reliably than the arthritis. therapeutic_modality is recorded as OTHER because this entry bundles two different platforms (a recombinant protein antagonist and a monoclonal antibody).

Mechanism Target:

Excess IL-1beta Production — Anakinra and canakinumab block IL-1 receptor signaling / IL-1beta downstream of IL-1beta overproduction.

Show evidence (4 references)

PMID:22161697 SUPPORT Human Clinical

"His disease has been well controlled on a regimen of anakinra."

A PAPA patient's disease was well controlled on anakinra (IL-1 blockade).

PMID:37610614 SUPPORT Other

"The IL-1 inhibitors used for the treatment of PG include anakinra (IL-1 receptor antagonist that blocks IL-1α and IL-1β) and canakinumab (IL-1β inhibitor)."

Identifies canakinumab, alongside anakinra, as an IL-1 inhibitor used therapeutically in this disease space.

PMID:37610614 SUPPORT INDIRECT Other

"These biologics have been particularly beneficial in patients with autosomal dominant autoinflammatory syndromes such as pyogenic arthritis, PG, acne (PAPA) spectrum disorder"

States that these IL-1-inhibiting biologics (anakinra, canakinumab) are particularly beneficial in PAPA-spectrum disease.

+ 1 more reference

TNF inhibition

Action: Pharmacotherapy NCIT:C15986

Agent: etanercept NCIT:C2381 infliximab NCIT:C1789 adalimumab NCIT:C65216

Platform: Other

TNF inhibitors (etanercept, infliximab, adalimumab) are effective, particularly for the cutaneous manifestations; TNF-alpha production is abnormally elevated in PAPA patients.

Mechanism Target:

Neutrophilic Sterile Inflammation — TNF blockade dampens the neutrophilic inflammatory response driving cutaneous lesions.

Show evidence (2 references)

PMID:15580218 SUPPORT Human Clinical

"After treatment with the tumor necrosis factor inhibitor etanercept, the disease underwent rapid and sustained clinical remission."

Etanercept produced rapid and sustained remission in a PAPA patient.

PMID:22161697 SUPPORT Human Clinical

"Good resolution of pyoderma gangrenosum was achieved in 3 patients with tumor necrosis factor α (TNFα) blockade treatment."

TNF-alpha blockade resolved pyoderma gangrenosum in 3 of 5 PAPA patients.

Corticosteroids

Action: Pharmacotherapy NCIT:C15986

Agent: corticosteroid CHEBI:50858

Platform: Small molecule

Systemic and intralesional/intra-articular corticosteroids are used as adjunct or bridging therapy for flares, limited by toxicity with prolonged use.

Show evidence (1 reference)

PMID:22161697 SUPPORT Human Clinical

"PG remitted briefly after the patient was treated with high-dose steroids."

High-dose steroids produced brief remission of pyoderma gangrenosum, illustrating corticosteroids as adjunct/bridge therapy.

Pathergy precautions (trauma and injection-site avoidance)

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Platform: Behavioral / lifestyle

Because minor trauma and needle sticks provoke sterile abscess formation (pathergy), avoidance of unnecessary skin trauma, injections, and elective surgery is a supportive measure to reduce injection-site and post-procedural flares.

Show evidence (1 reference)

PMID:22161697 SUPPORT INDIRECT Human Clinical

"Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"

Documents abscess formation at injection sites (pathergy), the observation that motivates avoiding unnecessary skin trauma and injections.

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Biochemical Markers

2

Interleukin-1 beta (peripheral blood leukocytes) (Elevated)

Context: Elevated IL-1beta production by peripheral blood leukocytes; the defining molecular readout of the pyrin-inflammasome mechanism.

Show evidence (1 reference)

PMID:21532836 SUPPORT Other

"elevated production of interleukin-1 beta (IL-1β) and tumor necrosis factor (TNFα) in peripheral blood leukocytes has been reported in more recent literature"

Reports elevated IL-1beta production by peripheral blood leukocytes in PAPA syndrome.

Tumor necrosis factor alpha (peripheral blood leukocytes) (Elevated)

Context: Elevated TNFalpha production by peripheral blood leukocytes, providing the rationale for TNF-inhibitor therapy.

Show evidence (1 reference)

PMID:21532836 SUPPORT Other

"elevated production of interleukin-1 beta (IL-1β) and tumor necrosis factor (TNFα) in peripheral blood leukocytes has been reported in more recent literature"

Reports elevated TNFalpha production by peripheral blood leukocytes in PAPA syndrome, substantiating the TNF-inhibition rationale.

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Diagnosis

2

Synovial fluid analysis

Arthrocentesis with synovial fluid cell counts distinguishes the sterile, neutrophil-rich (pyogenic) arthritis of PAPA syndrome from true septic arthritis; PAPA joint fluid shows exceedingly high, persistently sterile synovial cell counts, which is the central diagnostic crux when the clinical picture mimics infection.

synovial fluid cell count analysis NCIT:C220175

Results: Persistently high sterile synovial neutrophil counts distinguishing PAPA arthritis from septic arthritis.

Show evidence (1 reference)

PMID:28251506 SUPPORT Human Clinical

"Pyogenic arthritis, pyoderma gangrenosum and acne syndrome was diagnosed in a 42-year-old patient, after an unusual persistency of high synovial cell counts had been noticed."

Persistently high sterile synovial cell counts prompted the PAPA diagnosis, distinguishing it from septic arthritis.

PSTPIP1 molecular genetic testing

Because the classic PAPA-associated PSTPIP1 mutations (p.A230T, p.E250Q) are few and highly penetrant, targeted PSTPIP1 coding-sequence testing confirms the diagnosis and supports genetic counseling.

PSTPIP1 molecular genetic testing NCIT:C15709

Results: Identification of a pathogenic PSTPIP1 coding variant (classically p.A230T or p.E250Q).

Show evidence (1 reference)

PMID:21532836 SUPPORT Other

"a DNA sequence-based test for PSTPIP1 coding mutations is now commercially available"

A commercially available PSTPIP1 coding-sequence test is used to confirm the molecular diagnosis of PAPA syndrome.

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Prevalence

1

Worldwide (case reports and kindreds in the published literature)

Cases In Literature Ultra Rare

PAPA syndrome is exceptionally rare; the published literature consists of a small number of kindreds and sporadic cases rather than population-based rate estimates. No pooled numeric prevalence per 100,000 could be sourced, so the occurrence is recorded qualitatively as ultra-rare from the kindred/case counts.

Show evidence (1 reference)

PMID:22161697 SUPPORT Human Clinical

"The only 2 mutations described, A230T and E250Q, have been found in 7 kindreds"

Indicates the classic PAPA-causing variants had been reported in only a handful of kindreds, consistent with ultra-rare occurrence.

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Animal Models

1

PSTPIP1 A230T ectopic-expression mouse

Mice ectopically expressing mutant (A230T) PSTPIP1 show partial embryonic lethality, growth retardation, and elevated circulating proinflammatory cytokines, but do not develop the pyogenic arthritis or skin inflammation of human PAPA syndrome - a dissociation between the systemic cytokine phenotype and the organ-specific tissue lesions.

Species

Mouse

Genotype

Ectopic expression of human PAPA-associated PSTPIP1 A230T

Publication

PMID:23293022

Pathograph links

Excess IL-1beta Production partially recapitulates fidelity: low Mutant PSTPIP1 expression elevates circulating proinflammatory cytokines, recapitulating the systemic cytokine arm of PAPA.

Limitations: The model reports elevated circulating proinflammatory cytokines broadly rather than an IL-1beta-specific measurement, and the analysis concluded PSTPIP1 is not an essential regulator of the Nlrp3/Aim2/Nlrc4 inflammasomes in this system.

Show evidence (1 reference)

PMID:23293022 SUPPORT Model Organism

"ectopic expression of the mutant but not the wild type PSTPIP1 in mice lead to partial embryonic lethality, growth retardation, and elevated level of circulating proinflammatory cytokines."

Mutant PSTPIP1 raised circulating proinflammatory cytokines, partially modeling the systemic cytokine phenotype.

{ }

Source YAML

click to show

name: PAPA Syndrome
creation_date: '2026-09-03T00:00:00Z'
description: >-
  PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne) is a
  rare autosomal dominant monogenic autoinflammatory disease caused by heterozygous
  missense variants in PSTPIP1 (CD2BP1), classically p.A230T and p.E250Q in the
  coiled-coil domain. The variants severely reduce PSTPIP1 binding to the phosphatase
  PTP-PEST, leaving PSTPIP1 hyperphosphorylated with markedly increased avidity for
  pyrin; enhanced pyrin binding drives pyrin-inflammasome (ASC speck) assembly,
  caspase-1 activation, and IL-1beta overproduction, producing sterile neutrophilic
  inflammation that manifests as destructive pyogenic arthritis in childhood and,
  from puberty, pyoderma gangrenosum and severe cystic acne. IL-1 blockade and TNF
  inhibitors are the mainstay biologic therapies.
category: Mendelian
parents:
- Autoinflammatory Disease
- Inherited Disorder
disease_term:
  preferred_term: PAPA syndrome
  term:
    id: MONDO:0011462
    label: pyogenic arthritis-pyoderma gangrenosum-acne syndrome
inheritance:
- name: Autosomal dominant inheritance
  description: >-
    PAPA syndrome is inherited in an autosomal dominant manner from heterozygous
    PSTPIP1 missense variants, with incomplete penetrance and markedly variable
    expressivity documented both between and within families. Each child of an
    affected individual has a 50% risk of inheriting the variant.
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:21532836
    reference_title: "Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "PAPA syndrome (Pyogenic Arthritis, Pyoderma gangrenosum, and Acne) is an autosomal dominant, hereditary auto-inflammatory disease arising from mutations in the PSTPIP1/CD2BP1 gene on chromosome 15q."
    explanation: The review states PAPA syndrome is autosomal dominant and arises from PSTPIP1/CD2BP1 mutations on chromosome 15q.
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This analysis of 5 patients demonstrates that mutations in PSTPIP1 are incompletely penetrant and variably expressed in the PAPA syndrome."
    explanation: Documents incomplete penetrance and variable expressivity of PSTPIP1 variants in PAPA syndrome.
prevalence:
- population: Worldwide (case reports and kindreds in the published literature)
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    PAPA syndrome is exceptionally rare; the published literature consists of a
    small number of kindreds and sporadic cases rather than population-based rate
    estimates. No pooled numeric prevalence per 100,000 could be sourced, so the
    occurrence is recorded qualitatively as ultra-rare from the kindred/case counts.
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The only 2 mutations described, A230T and E250Q, have been found in 7 kindreds"
    explanation: Indicates the classic PAPA-causing variants had been reported in only a handful of kindreds, consistent with ultra-rare occurrence.
genetic:
- name: PSTPIP1
  association: Causative
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: PSTPIP1
    term:
      id: hgnc:9580
      label: PSTPIP1
  notes: >-
    Heterozygous missense variants in the coiled-coil domain of PSTPIP1 (also known
    as CD2BP1) cause PAPA syndrome. The two classic, functionally validated
    variants are p.A230T and p.E250Q; both severely reduce binding to PTP-PEST,
    leaving PSTPIP1 hyperphosphorylated with markedly increased avidity for pyrin.
    (Distinct PSTPIP1 variants such as p.E250K underlie the more severe PAMI
    phenotype and are outside the scope of this classic-PAPA entry.)
  evidence:
  - reference: PMID:11971877
    reference_title: "Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome, an autoinflammatory disorder."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "E250Q or A230T amino acid substitutions occur within a domain highly homologous to yeast cleavage furrow-associated protein CDC15."
    explanation: Identifies the two co-segregating PAPA-causing PSTPIP1/CD2BP1 missense substitutions in the coiled-coil domain.
  - reference: PMID:11971877
    reference_title: "Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome, an autoinflammatory disorder."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Yeast two-hybrid assays demonstrate severely reduced binding between PTP PEST and both the E250Q and A230T mutant proteins."
    explanation: Establishes the functional consequence of the causal variants - loss of PTP-PEST binding.
pathophysiology:
- name: Loss of PSTPIP1-PTP-PEST Binding
  description: >-
    PAPA-associated missense variants (p.A230T, p.E250Q) in the coiled-coil domain
    of PSTPIP1 severely reduce binding to the regulatory phosphatase PTP-PEST,
    releasing PSTPIP1 from dephosphorylation so that mutant protein accumulates in a
    hyperphosphorylated state. This loss of phosphatase engagement is the initiating
    molecular lesion; the resulting gain of function (enhanced pyrin binding) is
    modeled as the downstream node.
  biological_scale: MOLECULAR
  gene:
    preferred_term: PSTPIP1
    term:
      id: hgnc:9580
      label: PSTPIP1
  molecular_functions:
  - preferred_term: PTP-PEST (protein phosphatase) binding
    modifier: DECREASED
    term:
      id: GO:0019903
      label: protein phosphatase binding
  downstream:
  - target: Enhanced PSTPIP1-Pyrin Binding
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:14595024
      reference_title: "Pyrin binds the PSTPIP1/CD2BP1 protein, defining familial Mediterranean fever and PAPA syndrome as disorders in the same pathway."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "PAPA-associated A230T and E250Q PSTPIP1/CD2BP1 mutations markedly increased pyrin binding as assayed by immunoprecipitation and, relative to WT, these mutants were hyperphosphorylated when coexpressed with c-Abl kinase."
      explanation: Links reduced PTP-PEST engagement (hyperphosphorylation) directly to increased pyrin binding.
  evidence:
  - reference: PMID:11971877
    reference_title: "Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome, an autoinflammatory disorder."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Yeast two-hybrid assays demonstrate severely reduced binding between PTP PEST and both the E250Q and A230T mutant proteins."
    explanation: The causal variants abolish PTP-PEST binding, the initiating molecular lesion.
- name: Enhanced PSTPIP1-Pyrin Binding
  description: >-
    Hyperphosphorylated mutant PSTPIP1 binds pyrin (the MEFV gene product) with
    markedly increased avidity, mechanistically placing PAPA syndrome in the same
    pyrin pathway as familial Mediterranean fever.
  biological_scale: MOLECULAR
  downstream:
  - target: Pyrin Inflammasome Assembly
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:19584923
      reference_title: "Pyrin Modulates the Intracellular Distribution of PSTPIP1."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "PSTPIP1 molecules with PAPA-associated mutations are recruited by pyrin to ASC specks with particularly high efficiency, suggesting a unique mechanism underlying the robust inflammatory phenotype of PAPA syndrome."
      explanation: Enhanced pyrin binding recruits mutant PSTPIP1 into ASC specks (inflammasome assembly) with high efficiency.
  evidence:
  - reference: PMID:14595024
    reference_title: "Pyrin binds the PSTPIP1/CD2BP1 protein, defining familial Mediterranean fever and PAPA syndrome as disorders in the same pathway."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Endogenous PSTPIP1/CD2BP1 and pyrin are coexpressed in monocytes and granulocytes and can be coimmunoprecipitated from THP-1 cells."
    explanation: Demonstrates the physical PSTPIP1-pyrin interaction that the PAPA mutations amplify.
  - reference: PMID:19584923
    reference_title: "Pyrin Modulates the Intracellular Distribution of PSTPIP1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Since disease-associated mutations in PSTPIP1 enhance pyrin binding, PAPA syndrome and FMF are thought to share a common pathoetiology."
    explanation: States that PAPA-associated PSTPIP1 mutations enhance pyrin binding.
- name: Pyrin Inflammasome Assembly
  description: >-
    Increased pyrin engagement drives assembly of the pyrin inflammasome (ASC
    specks) and caspase-1 activation, escaping the normal PTP-PEST/pyrin
    autoinhibitory checkpoint.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: monocyte
    term:
      id: CL:0000576
      label: monocyte
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: pyrin inflammasome complex assembly
    modifier: GAIN_OF_FUNCTION
    term:
      id: GO:0140632
      label: canonical inflammasome complex assembly
  downstream:
  - target: Excess IL-1beta Production
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:19584923
      reference_title: "Pyrin Modulates the Intracellular Distribution of PSTPIP1."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "ASC specks are associated with inflammasome activity."
      explanation: Ties the ASC speck assembly node to downstream inflammasome (caspase-1/IL-1beta) activity.
  evidence:
  - reference: PMID:19584923
    reference_title: "Pyrin Modulates the Intracellular Distribution of PSTPIP1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "PSTPIP1 molecules with PAPA-associated mutations are recruited by pyrin to ASC specks with particularly high efficiency, suggesting a unique mechanism underlying the robust inflammatory phenotype of PAPA syndrome."
    explanation: Direct evidence for enhanced pyrin-inflammasome (ASC speck) assembly by PAPA-mutant PSTPIP1.
- name: Excess IL-1beta Production
  description: >-
    Pyrin-inflammasome activation cleaves pro-IL-1beta via caspase-1, producing
    IL-1beta overproduction that is a defining molecular feature of PAPA syndrome
    and is measurable as markedly elevated IL-1beta in patients.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: monocyte
    term:
      id: CL:0000576
      label: monocyte
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: interleukin-1 beta production
    modifier: INCREASED
    term:
      id: GO:0032611
      label: interleukin-1 beta production
  downstream:
  - target: Neutrophilic Sterile Inflammation
    causal_link_type: DIRECT
  - target: Elevated CRP
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:21532836
    reference_title: "Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Overproduction of IL-1β is a clear molecular feature of PAPA syndrome."
    explanation: States IL-1beta overproduction as a defining molecular feature of PAPA syndrome.
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Interleukin-1β (IL-1β) and circulating neutrophil granule enzyme levels were markedly elevated in patients compared to those in controls."
    explanation: Measures markedly elevated IL-1beta in PAPA patients versus controls.
  - reference: PMID:14595024
    reference_title: "Pyrin binds the PSTPIP1/CD2BP1 protein, defining familial Mediterranean fever and PAPA syndrome as disorders in the same pathway."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we found increased IL-1beta production by peripheral blood leukocytes from a clinically active PAPA patient with the A230T PSTPIP1/CD2BP1 mutation and in cell lines transfected with both PAPA-associated mutants."
    explanation: Demonstrates increased IL-1beta production in cells from a PAPA patient and in mutant-transfected cell lines.
- name: Neutrophilic Sterile Inflammation
  description: >-
    IL-1-driven recruitment of neutrophils produces sterile, neutrophil-rich
    (pyogenic) inflammation of joints and skin; recurring episodes accumulate
    sterile pyogenic material in affected joints, ultimately causing destruction,
    and drive the cutaneous lesions.
  biological_scale: TISSUE
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: production of molecular mediator involved in inflammatory response
    modifier: INCREASED
    term:
      id: GO:0002532
      label: production of molecular mediator involved in inflammatory response
  downstream:
  - target: Sterile pyogenic arthritis
    causal_link_type: DIRECT
  - target: Progressive joint destruction
    causal_link_type: DIRECT
  - target: Pyoderma gangrenosum
    causal_link_type: DIRECT
  - target: Cystic acne
    causal_link_type: DIRECT
  - target: Positive pathergy test
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:11971877
    reference_title: "Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome, an autoinflammatory disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recurring inflammatory episodes lead to accumulation of sterile, pyogenic, neutrophil-rich material within the affected joints, ultimately resulting in significant destruction."
    explanation: Describes the sterile neutrophil-rich joint inflammation and resulting destruction.
- name: PSTPIP1 Cytoskeletal Adaptor Dysregulation
  description: >-
    Beyond the inflammasome arm, PSTPIP1 is an F-BAR/SH3 cytoskeletal adaptor that
    links CD2 to WASP-driven actin polymerization at the immunological synapse and
    regulates myeloid-cell migration. Perturbation of this cytoskeletal-regulatory
    function is proposed to contribute to the exaggerated neutrophil influx at sites
    of minor trauma (pathergy); the link to pathergy is inferential rather than
    demonstrated.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: T cell
    term:
      id: CL:0000084
      label: T cell
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: actin filament organization
    term:
      id: GO:0007015
      label: actin filament organization
  downstream:
  - target: Neutrophilic Sterile Inflammation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:12530983
    reference_title: "The Wiskott-Aldrich syndrome protein acts downstream of CD2 and the CD2AP and PSTPIP1 adaptors to promote formation of the immunological synapse."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: "PSTPIP1 acts downstream of CD2/CD2AP to link CD2 engagement to the WASp-evoked actin polymerization required for synapse formation and T cell activation."
    explanation: Establishes PSTPIP1's cytoskeletal adaptor role; its contribution to pathergy in PAPA is an inference from this normal function.
phenotypes:
- name: Sterile pyogenic arthritis
  category: Phenotype
  description: >-
    Recurrent sterile, erosive (pyogenic) arthritis beginning in childhood,
    occurring spontaneously or after minor trauma; synovial fluid shows very high
    sterile neutrophil counts. Joint symptoms tend to subside by puberty.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Sterile pyogenic arthritis
    term:
      id: HP:0040310
      label: Sterile arthritis
    temporality: RECURRENT
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PAPA syndrome typically presents with recurrent sterile, erosive arthritis in childhood, occurring spontaneously or after minor trauma, occasionally resulting in significant joint destruction. By puberty, joint symptoms tend to subside and cutaneous symptoms increase."
    explanation: Describes the childhood-onset recurrent sterile erosive arthritis and its temporal course.
  - reference: PMID:28251506
    reference_title: "Pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome: differential diagnosis of septic arthritis by regular detection of exceedingly high synovial cell counts."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pyogenic arthritis, pyoderma gangrenosum and acne syndrome was diagnosed in a 42-year-old patient, after an unusual persistency of high synovial cell counts had been noticed."
    explanation: Documents the persistently high sterile synovial cell counts characteristic of the arthritis.
- name: Progressive joint destruction
  category: Phenotype
  description: >-
    Repeated destructive arthritis flares can produce significant, cumulative joint
    destruction if inadequately controlled in childhood.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Progressive joint destruction
    term:
      id: HP:0005187
      label: Progressive joint destruction
  evidence:
  - reference: PMID:11971877
    reference_title: "Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome, an autoinflammatory disorder."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recurring inflammatory episodes lead to accumulation of sterile, pyogenic, neutrophil-rich material within the affected joints, ultimately resulting in significant destruction."
    explanation: Recurrent sterile joint inflammation ultimately produces significant joint destruction.
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "recurrent sterile, erosive arthritis in childhood, occurring spontaneously or after minor trauma, occasionally resulting in significant joint destruction"
    explanation: States that significant joint destruction results only occasionally, supporting the OCCASIONAL frequency.
- name: Pyoderma gangrenosum
  category: Phenotype
  description: >-
    Recurrent, nonhealing sterile skin ulcers (pyoderma gangrenosum), typically
    emerging from puberty/adolescence and often triggered by minor trauma.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Pyoderma gangrenosum
    term:
      id: HP:0025452
      label: Pyoderma gangrenosum
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"
    explanation: Lists pyoderma gangrenosum (recurrent nonhealing sterile ulcers) among the cutaneous manifestations.
- name: Cystic acne
  category: Phenotype
  description: >-
    Severe cystic/nodulocystic acne, often scarring, typically appearing around or
    after puberty.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Severe cystic acne
    term:
      id: HP:0033188
      label: Cystic acne
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"
    explanation: Lists severe cystic acne among the cutaneous manifestations.
- name: Positive pathergy test
  category: Phenotype
  description: >-
    Exaggerated inflammatory response with sterile abscess formation at sites of
    minor injury or injection (pathergy), a hallmark clinical sign.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Pathergy
    term:
      id: HP:0025532
      label: Positive pathergy test
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"
    explanation: Names pathergy (abscesses at injection sites) as a cutaneous manifestation.
- name: Elevated CRP
  category: Laboratory
  description: Elevated acute-phase reactants during inflammatory flares.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Elevated C-reactive protein
    term:
      id: HP:0011227
      label: Elevated circulating C-reactive protein concentration
    temporality: ACUTE
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    directness: DIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "Levels of the acute-phase reactants C-reactive protein (CRP) and lipopolysaccharide binding protein and of the enzyme matrix metalloproteinase 9 were also significantly elevated compared to those in controls (Figure 2)."
    explanation: Measures significantly elevated CRP (an acute-phase reactant) in PAPA patients compared with controls.
diagnosis:
- name: Synovial fluid analysis
  description: >-
    Arthrocentesis with synovial fluid cell counts distinguishes the sterile,
    neutrophil-rich (pyogenic) arthritis of PAPA syndrome from true septic
    arthritis; PAPA joint fluid shows exceedingly high, persistently sterile
    synovial cell counts, which is the central diagnostic crux when the clinical
    picture mimics infection.
  diagnosis_term:
    preferred_term: synovial fluid cell count analysis
    term:
      id: NCIT:C220175
      label: Synovial Fluid Cell Count with Differential
  results: Persistently high sterile synovial neutrophil counts distinguishing PAPA arthritis from septic arthritis.
  evidence:
  - reference: PMID:28251506
    reference_title: "Pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome: differential diagnosis of septic arthritis by regular detection of exceedingly high synovial cell counts."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pyogenic arthritis, pyoderma gangrenosum and acne syndrome was diagnosed in a 42-year-old patient, after an unusual persistency of high synovial cell counts had been noticed."
    explanation: Persistently high sterile synovial cell counts prompted the PAPA diagnosis, distinguishing it from septic arthritis.
- name: PSTPIP1 molecular genetic testing
  description: >-
    Because the classic PAPA-associated PSTPIP1 mutations (p.A230T, p.E250Q) are
    few and highly penetrant, targeted PSTPIP1 coding-sequence testing confirms
    the diagnosis and supports genetic counseling.
  diagnosis_term:
    preferred_term: PSTPIP1 molecular genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  results: Identification of a pathogenic PSTPIP1 coding variant (classically p.A230T or p.E250Q).
  evidence:
  - reference: PMID:21532836
    reference_title: "Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "a DNA sequence-based test for PSTPIP1 coding mutations is now commercially available"
    explanation: A commercially available PSTPIP1 coding-sequence test is used to confirm the molecular diagnosis of PAPA syndrome.
treatments:
- name: IL-1 blockade (anakinra, canakinumab)
  description: >-
    Interleukin-1 blockade is the mainstay biologic strategy, targeting the
    IL-1beta-driven mechanism and most effective for the arthritis component. The
    recombinant IL-1 receptor antagonist anakinra and the anti-IL-1beta monoclonal
    antibody canakinumab are both used; the cutaneous manifestations (particularly
    cystic acne) respond less reliably than the arthritis. therapeutic_modality is
    recorded as OTHER because this entry bundles two different platforms (a
    recombinant protein antagonist and a monoclonal antibody).
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: anakinra
      term:
        id: NCIT:C38717
        label: Anakinra
    - preferred_term: canakinumab
      term:
        id: NCIT:C80971
        label: Canakinumab
  target_mechanisms:
  - target: Excess IL-1beta Production
    description: Anakinra and canakinumab block IL-1 receptor signaling / IL-1beta downstream of IL-1beta overproduction.
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "His disease has been well controlled on a regimen of anakinra."
    explanation: A PAPA patient's disease was well controlled on anakinra (IL-1 blockade).
  - reference: PMID:37610614
    reference_title: "Pyoderma Gangrenosum: Treatment Options."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The IL-1 inhibitors used for the treatment of PG include anakinra (IL-1 receptor antagonist that blocks IL-1α and IL-1β) and canakinumab (IL-1β inhibitor)."
    explanation: Identifies canakinumab, alongside anakinra, as an IL-1 inhibitor used therapeutically in this disease space.
  - reference: PMID:37610614
    reference_title: "Pyoderma Gangrenosum: Treatment Options."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: OTHER
    snippet: "These biologics have been particularly beneficial in patients with autosomal dominant autoinflammatory syndromes such as pyogenic arthritis, PG, acne (PAPA) spectrum disorder"
    explanation: States that these IL-1-inhibiting biologics (anakinra, canakinumab) are particularly beneficial in PAPA-spectrum disease.
  - reference: PMID:21532836
    reference_title: "Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review."
    supports: REFUTE
    evidence_source: OTHER
    snippet: "cystic acne, the second cutaneous symptom of PAPA syndrome, does not seem as responsive to IL1β and TNFα blockade"
    explanation: Qualifies the efficacy claim - cystic acne responds less reliably to IL-1beta (and TNFalpha) blockade than the arthritis and pyoderma gangrenosum do.
- name: TNF inhibition
  description: >-
    TNF inhibitors (etanercept, infliximab, adalimumab) are effective, particularly
    for the cutaneous manifestations; TNF-alpha production is abnormally elevated in
    PAPA patients.
  therapeutic_modality: OTHER
  notes: >-
    therapeutic_modality is OTHER because the agents span platforms - infliximab and
    adalimumab are monoclonal antibodies while etanercept is a soluble TNF-receptor
    fusion protein - so no single modality value describes the entry.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: etanercept
      term:
        id: NCIT:C2381
        label: Etanercept
    - preferred_term: infliximab
      term:
        id: NCIT:C1789
        label: Infliximab
    - preferred_term: adalimumab
      term:
        id: NCIT:C65216
        label: Adalimumab
  target_mechanisms:
  - target: Neutrophilic Sterile Inflammation
    description: TNF blockade dampens the neutrophilic inflammatory response driving cutaneous lesions.
  evidence:
  - reference: PMID:15580218
    reference_title: "Abnormal production of tumor necrosis factor (TNF) -- alpha and clinical efficacy of the TNF inhibitor etanercept in a patient with PAPA syndrome [corrected]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "After treatment with the tumor necrosis factor inhibitor etanercept, the disease underwent rapid and sustained clinical remission."
    explanation: Etanercept produced rapid and sustained remission in a PAPA patient.
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Good resolution of pyoderma gangrenosum was achieved in 3 patients with tumor necrosis factor α (TNFα) blockade treatment."
    explanation: TNF-alpha blockade resolved pyoderma gangrenosum in 3 of 5 PAPA patients.
- name: Corticosteroids
  description: >-
    Systemic and intralesional/intra-articular corticosteroids are used as adjunct
    or bridging therapy for flares, limited by toxicity with prolonged use.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: corticosteroid
      term:
        id: CHEBI:50858
        label: corticosteroid
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PG remitted briefly after the patient was treated with high-dose steroids."
    explanation: High-dose steroids produced brief remission of pyoderma gangrenosum, illustrating corticosteroids as adjunct/bridge therapy.
- name: Pathergy precautions (trauma and injection-site avoidance)
  description: >-
    Because minor trauma and needle sticks provoke sterile abscess formation
    (pathergy), avoidance of unnecessary skin trauma, injections, and elective
    surgery is a supportive measure to reduce injection-site and post-procedural
    flares.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:22161697
    reference_title: "Brief report: genotype, phenotype, and clinical course in five patients with PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne)."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cutaneous manifestations include pathergy, frequently with abscesses at the sites of injections, severe cystic acne, and recurrent nonhealing sterile ulcers, often diagnosed as PG"
    explanation: Documents abscess formation at injection sites (pathergy), the observation that motivates avoiding unnecessary skin trauma and injections.
biochemical:
- name: Interleukin-1 beta (peripheral blood leukocytes)
  presence: Elevated
  context: Elevated IL-1beta production by peripheral blood leukocytes; the defining molecular readout of the pyrin-inflammasome mechanism.
  biomarker_term:
    preferred_term: Interleukin-1 Beta
    term:
      id: NCIT:C20522
      label: Interleukin-1 Beta
  evidence:
  - reference: PMID:21532836
    reference_title: "Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "elevated production of interleukin-1 beta (IL-1β) and tumor necrosis factor (TNFα) in peripheral blood leukocytes has been reported in more recent literature"
    explanation: Reports elevated IL-1beta production by peripheral blood leukocytes in PAPA syndrome.
- name: Tumor necrosis factor alpha (peripheral blood leukocytes)
  presence: Elevated
  context: Elevated TNFalpha production by peripheral blood leukocytes, providing the rationale for TNF-inhibitor therapy.
  biomarker_term:
    preferred_term: Tumor Necrosis Factor
    term:
      id: NCIT:C20535
      label: Tumor Necrosis Factor
  evidence:
  - reference: PMID:21532836
    reference_title: "Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "elevated production of interleukin-1 beta (IL-1β) and tumor necrosis factor (TNFα) in peripheral blood leukocytes has been reported in more recent literature"
    explanation: Reports elevated TNFalpha production by peripheral blood leukocytes in PAPA syndrome, substantiating the TNF-inhibition rationale.
animal_models:
- name: PSTPIP1 A230T ectopic-expression mouse
  species: Mouse
  genotype: Ectopic expression of human PAPA-associated PSTPIP1 A230T
  description: >-
    Mice ectopically expressing mutant (A230T) PSTPIP1 show partial embryonic
    lethality, growth retardation, and elevated circulating proinflammatory
    cytokines, but do not develop the pyogenic arthritis or skin inflammation of
    human PAPA syndrome - a dissociation between the systemic cytokine phenotype and
    the organ-specific tissue lesions.
  publication: PMID:23293022
  modeled_mechanisms:
  - target: Excess IL-1beta Production
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      Mutant PSTPIP1 expression elevates circulating proinflammatory cytokines,
      recapitulating the systemic cytokine arm of PAPA.
    limitations: >-
      The model reports elevated circulating proinflammatory cytokines broadly
      rather than an IL-1beta-specific measurement, and the analysis concluded
      PSTPIP1 is not an essential regulator of the Nlrp3/Aim2/Nlrc4 inflammasomes
      in this system.
    evidence:
    - reference: PMID:23293022
      reference_title: "Inflammation in mice ectopically expressing human Pyogenic Arthritis, Pyoderma Gangrenosum, and Acne (PAPA) Syndrome-associated PSTPIP1 A230T mutant proteins."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "ectopic expression of the mutant but not the wild type PSTPIP1 in mice lead to partial embryonic lethality, growth retardation, and elevated level of circulating proinflammatory cytokines."
      explanation: Mutant PSTPIP1 raised circulating proinflammatory cytokines, partially modeling the systemic cytokine phenotype.
  - target: Sterile pyogenic arthritis
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      The mouse model does not reproduce the defining pyogenic arthritis or skin
      inflammation of human PAPA syndrome.
    limitations: >-
      Despite systemic cytokine elevation, the mice fail to develop the pyogenic
      arthritis and skin inflammation that define human PAPA, indicating the
      organ-specific lesion formation is not captured by this model.
    evidence:
    - reference: PMID:23293022
      reference_title: "Inflammation in mice ectopically expressing human Pyogenic Arthritis, Pyoderma Gangrenosum, and Acne (PAPA) Syndrome-associated PSTPIP1 A230T mutant proteins."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "common features of human PAPA syndrome such as pyogenic arthritis and skin inflammation were not recapitulated in the mouse model"
      explanation: The model explicitly fails to reproduce the pyogenic arthritis and skin inflammation of human PAPA.
discussions:
- discussion_id: papa_a230t_mouse_model_mismatch
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Neutrophilic Sterile Inflammation
  prompt: >-
    Why does the PSTPIP1 A230T mouse reproduce systemic cytokine elevation but not
    the joint and skin lesions that define human PAPA syndrome?
  rationale: >-
    The A230T mouse recapitulates the inflammasome/cytokine arm (elevated
    circulating proinflammatory cytokines) yet fails to develop pyogenic arthritis
    or skin inflammation, so the causal step from IL-1-driven systemic inflammation
    to organ-specific neutrophilic tissue lesions is not established in vivo and may
    depend on species- or context-specific factors absent from the model.
references:
- reference: PMID:11971877
  title: "Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome, an autoinflammatory disorder."
- reference: PMID:14595024
  title: "Pyrin binds the PSTPIP1/CD2BP1 protein, defining familial Mediterranean fever and PAPA syndrome as disorders in the same pathway."
- reference: PMID:21532836
  title: "Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review."
- reference: PMID:37610614
  title: "Pyoderma Gangrenosum: Treatment Options."

📚

References & Deep Research

References

4

PMID:11971877

Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome, an autoinflammatory disorder.

No top-level findings curated for this source.

PMID:14595024

Pyrin binds the PSTPIP1/CD2BP1 protein, defining familial Mediterranean fever and PAPA syndrome as disorders in the same pathway.

No top-level findings curated for this source.

PMID:21532836

Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review.

No top-level findings curated for this source.

PMID:37610614

Pyoderma Gangrenosum: Treatment Options.

No top-level findings curated for this source.

Deep Research

1

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.

Evaluations and curation notes (1)

Create: PAPA Syndrome · 2026-09-03T15:30:33Z · View source

De-novo curation of PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne; MONDO:0011462; PSTPIP1/hgnc:9580, autosomal dominant). Deep research via 'just research-disorder claude_code' (report committed under research/). All references fetched with just fetch-reference and every snippet verified against the cache (30/30). Pathograph built as a causal chain: reduced PTP-PEST binding -> hyperphosphorylated PSTPIP1 -> increased pyrin binding -> pyrin-inflammasome (ASC speck) assembly -> IL-1beta overproduction -> neutrophilic sterile inflammation -> arthritis/PG/cystic acne/pathergy, plus a parallel cytoskeletal-adaptor branch. Anchor refs: Wise 2002 PMID:11971877 (CD2BP1 mutations; note the task-hinted PMID:12432392 was verified WRONG - a Nature neuroscience paper - and corrected), Shoham 2003 PMID:14595024 (pyrin binding, hyperphosphorylation, IL-1beta), Waite 2009 PMID:19584923 (ASC speck recruitment). A230T mouse model PMID:23293022 recorded as PARTIALLY_RECAPITULATES cytokine node / FAILS_TO_RECAPITULATE arthritis, with a HUMAN_MODEL_MISMATCH discussion. Treatments: IL-1 blockade (anakinra), TNF inhibition (etanercept/infliximab/adalimumab), corticosteroids. Deep-research errors caught and corrected during curation: HGNC:9581 (=PSTPIP2 paralog) -> hgnc:9580; HP:0031928 -> HP:0025452 (pyoderma gangrenosum); HP:0033798 (obsolete) -> HP:0040310 (sterile arthritis). No pyrin/IL-1 mechanism module exists in kb/modules and FMF declares no conforms_to, so none added. Validated: just validate, validate-terms, count-verified-snippets 30/30, check-causal-targets, check-duplicate-keys, check-entity-refs, check-qualifier-terms, and authoritative validate-disorders all pass.

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-sonnet-5 31 citations 2026-09-03T14:57:13.514311

1. Disease Information

Overview. PAPA syndrome is a rare, autosomal dominant monogenic autoinflammatory disorder caused by heterozygous pathogenic variants in PSTPIP1 (proline-serine-threonine phosphatase-interacting protein 1, also historically named CD2BP1), located at 15q24.3. It is the prototype of a broader "PSTPIP1-associated inflammatory diseases" (PAID) spectrum. It was first delineated clinically by Lindor et al. (1997) as "a new autosomal dominant disorder of pyogenic sterile arthritis, pyoderma gangrenosum, and acne" (ScienceDirect summary), and the causal gene was identified by Wise et al., Human Molecular Genetics 2002 (PMID not directly returned by search but DOI 10.1093/hmg/11.8.961), who found co-segregating CD2BP1/PSTPIP1 mutations (p.E250Q, p.A230T) in two multiplex families and showed by yeast two-hybrid assay that both severely reduce binding to PTP-PEST (Wise et al. 2002).

Key identifiers: - OMIM: 604416 — "Pyogenic Sterile Arthritis, Pyoderma Gangrenosum, and Acne" (OMIM:604416) - Orphanet: ORPHA:69126 (Orphanet) - MONDO: MONDO:0011462 (Wikidata cross-reference) - Gene: PSTPIP1 (HGNC:9581), chr15q24.3, also historically CD2BP1 - Common synonyms: PAPA syndrome; Pyogenic Arthritis-Pyoderma Gangrenosum-Acne syndrome; Familial recurrent arthritis

Evidence basis. Almost all published data derive from aggregated case reports/case series and family pedigrees (individual-patient level, not large-cohort EHR data) — this is one of the rarest monogenic autoinflammatory diseases, with the literature dominated by single-family and small-series reports rather than registries.

2. Etiology

Disease causal factor — genetic, single-gene, autosomal dominant. PAPA syndrome is caused by heterozygous missense variants in PSTPIP1. The two "classic," functionally validated PAPA-causing variants are p.A230T and p.E250Q (originally reported as E250Q; some literature also refers to it as E250K in the context of the related PAMI phenotype — see below), both located in the coiled-coil domain of PSTPIP1 and both shown to abolish binding to the phosphatase PTP-PEST by yeast two-hybrid assay (Wise 2002). Additional variants — p.D246N and p.E257G — are classified as "likely pathogenic" based on absence from population databases, location within the same critical PSTPIP1 domain, and de novo occurrence without family history (Frontiers Genetics case report/review, 2026).

Genetic risk factors. The causal variants themselves are the dominant risk factor; PAPA syndrome shows autosomal dominant inheritance with incomplete penetrance and variable expressivity — even within the same family and the same variant, disease severity and organ involvement vary substantially (PMC3737487, genotype-phenotype study of 5 patients). No environmental cause is established; physical trauma is a recognized trigger of flares (pathergy) rather than a cause.

Gene-environment interaction. The clearest gene-environment interplay is pathergy — minor trauma or injection precipitates sterile abscesses and joint flares in genetically susceptible (PSTPIP1-mutant) individuals, attributed to dysregulated neutrophil recruitment and IL-1β hyperproduction at sites of minor injury.

Protective factors. None are established in the literature; this is expected for an ultra-rare, highly penetrant single-gene autosomal dominant disorder.

3. Phenotypes

Articular

Sterile pyogenic (destructive) arthritis — HP:0033798 (Sterile pyogenic arthritis) or generically HP:0001369 (Arthritis). Recurrent, migratory, typically monoarticular flares, most often affecting elbows, knees, and ankles; occurs spontaneously or after minor trauma; leads to accumulation of sterile purulent synovial fluid and, if untreated, joint destruction (PMC3737487; imaging review, Pediatric Radiology 2018). Synovial fluid shows exceedingly high (often >100,000/mm³) sterile neutrophilic white cell counts, a key differentiator from true septic arthritis (PubMed 28251506).
Onset: typically early childhood.
Course: arthritis tends to subside by/after puberty as cutaneous disease intensifies.

Cutaneous

Pyoderma gangrenosum (HP:0031928 or general "cutaneous ulceration") — recurrent, non-healing, sterile skin ulcers, often triggered by minor trauma (pathergy). Onset generally later than arthritis — adolescence/early adulthood.
Severe cystic/nodulocystic acne (HP:0001061 Acne inversa / cystic acne terms) — often severe and scarring, emerging around/after puberty.
Pathergy — exaggerated inflammatory response and sterile abscess formation at injection or injury sites (a hallmark clinical sign, similar to Behçet disease pathergy).
Suppurative/pyogenic skin abscesses; in the extended PAID spectrum, hidradenitis suppurativa (see PASH/PAPASH below).

Laboratory abnormalities

Elevated acute-phase reactants during flares (ESR, CRP).
Markedly elevated IL-1β and circulating neutrophil granule enzymes compared to controls (PMC3737487).
In the PAMI end of the spectrum: hyperzincemia, hypercalprotectinemia (very high S100A8/A9 / MRP8-14), cytopenias.

Phenotype pattern: temporal segregation is a defining clinical feature — arthritis dominates in childhood, and cutaneous disease (PG, acne) dominates from puberty onward, though this is variable between and within families (incomplete penetrance/variable expressivity).

Quality of life impact. Disfiguring/scarring skin disease (PG scars, cystic acne scarring) and destructive arthritis both carry substantial psychosocial and functional burden; specific EQ-5D/SF-36 data for PAPA syndrome were not identified in this search and are likely absent given disease rarity — flag as a gap.

4. Genetic/Molecular Information

Causal gene: PSTPIP1 / HGNC:9581, chr15q24.3; OMIM gene entry 606347 (gene), disease entry 604416.

Pathogenic variants (classic/validated): | Variant | Classification | Domain | Functional evidence | |---|---|---|---| | p.A230T | Pathogenic | Coiled-coil | Segregates in families; disrupts PTP-PEST binding, ↑pyrin binding | | p.E250Q | Pathogenic | Coiled-coil | Segregates in families; disrupts PTP-PEST binding, ↑pyrin binding | | p.D246N | Likely pathogenic | Coiled-coil | De novo, absent from population DBs | | p.E257G | Likely pathogenic | Coiled-coil | De novo, absent from population DBs |

A recent systematic review of PAMI-spectrum cases found 41/43 (95%) carried the heterozygous p.E250K variant (PMC10454568, PAMI systematic review, 2023) — note this is a distinct variant from the classic PAPA-causing E250Q, illustrating allelic heterogeneity across the PSTPIP1-associated disease spectrum (genotype–phenotype correlations discussed further under §9).

Variant type/class: All known causal variants are missense, clustered in the coiled-coil domain of PSTPIP1.

Functional consequence — gain-of-function/dominant-negative-type effect at the protein-interaction level: PAPA-associated PSTPIP1 mutants show reduced binding to PTP-PEST, leading to hyperphosphorylation of PSTPIP1 and consequent markedly increased affinity for pyrin (MEFV) (PLOS ONE, PMC2702820; [WebSearch synthesis of PSTPIP1-pyrin mechanism]). This is a molecular gain-of-interaction rather than classic enzymatic gain/loss of function.

Modifier considerations: No formal modifier genes are established, but marked intrafamilial variable expressivity (documented in the same 5-patient genotype-phenotype series) implies unidentified genetic or stochastic modifiers (PMC3737487).

Allele frequency: These variants are private/rare, essentially absent from population databases (gnomAD) consistent with high penetrance dominant disease-causing status; specific allele-frequency figures were not returned by this search pass.

Epigenetics/chromosomal abnormalities: Not applicable — PAPA syndrome is a point-mutation Mendelian disorder; no epigenetic mechanism or copy-number/translocation etiology is described in the literature surveyed.

5. Environmental Information

Physical trauma / minor injury is the principal recognized environmental trigger, producing the pathergy phenomenon at both joint and skin sites.
No specific toxin, infectious agent, or occupational exposure is implicated as causal; this is consistent with a fully genetically determined disease.
No infectious trigger is causal, although the arthritis and skin lesions can be clinically mistaken for infection (hence "pyogenic," "gangrenosum" naming) — a critical differential-diagnosis point rather than a true infectious etiology.

6. Mechanism / Pathophysiology

Causal chain (numbered, from mutation to clinical manifestation):

A heterozygous missense variant (e.g., p.A230T, p.E250Q) in the coiled-coil domain of PSTPIP1 leads to markedly reduced binding affinity between PSTPIP1 and the tyrosine phosphatase PTP-PEST (demonstrated by yeast two-hybrid; Wise 2002).
Reduced PTP-PEST engagement results in loss of PTP-PEST-mediated dephosphorylation of PSTPIP1, so mutant PSTPIP1 accumulates in a hyperphosphorylated state (PMC2702820).
Hyperphosphorylated PSTPIP1 leads to markedly increased binding affinity for pyrin (encoded by MEFV, the familial Mediterranean fever gene) — mechanistically linking PAPA syndrome to the same pyrin-inflammasome pathway as FMF (PNAS, pyrin-PSTPIP1 binding paper; [WebSearch synthesis]).
Enhanced pyrin–PSTPIP1 binding results in pyrin being recruited (via PSTPIP1) into ASC specks with unusually high efficiency — i.e., PAPA-mutant PSTPIP1 promotes assembly of the pyrin inflammasome (PMC2702820).
Pyrin inflammasome assembly activates caspase-1, which cleaves pro-IL-1β and pro-IL-18 into their active, secreted forms ([WebSearch synthesis, pyrin-inflammasome-caspase-1-IL-1β cascade]).
IL-1β/IL-18 overproduction, together with dysregulated neutrophil chemotaxis (PSTPIP1's independent cytoskeletal role — see step 7), drives local and systemic sterile neutrophilic inflammation.
Branch — cytoskeletal/adaptor arm (parallel, upstream-independent of inflammasome): wild-type PSTPIP1 is an F-BAR–domain cytoskeleton-associated adaptor that (a) in T cells, bridges CD2 to WASP (Wiskott-Aldrich syndrome protein), coupling TCR engagement to actin polymerization required for immunological synapse formation (PubMed 12530983); and (b) in neutrophils/macrophages, localizes to the trailing uropod edge with PIP5K1C/DNM2 to regulate migration, and controls extracellular-matrix degradation and filopodia formation via podosome regulation (Blood, ASH publications). PAPA-mutant PSTPIP1 perturbs this cytoskeletal-regulatory function, contributing to exaggerated neutrophil influx at sites of minor trauma — the cellular basis of pathergy.
Excess IL-1β/IL-18 signaling plus exaggerated, trauma-triggered neutrophil infiltration culminate in the clinical triad: sterile pyogenic (neutrophil-rich) destructive arthritis, pyoderma gangrenosum ulceration, and severe cystic acne — with a temporal pattern in which arthritis predominates in childhood (when trauma/joint use is high) and cutaneous disease predominates from puberty onward (hormonally influenced acne, ongoing pathergy-driven ulceration).

Inferential note: the step linking hyperphosphorylation directly to increased pyrin binding (step 3) and the step linking cytoskeletal dysregulation quantitatively to pathergy severity (step 7→8) are supported mainly by in vitro biochemical and cell-biology studies; direct demonstration that this cascade alone (absent the cytoskeletal arm) is sufficient to produce the full clinical triad in vivo is not established — the mouse model data (below) show a dissociation between systemic cytokine elevation and clinical skin/joint phenotype, indicating the causal chain from IL-1β elevation to organ-specific lesion formation is incompletely modeled.

Molecular pathways: pyrin (MEFV) inflammasome pathway; IL-1β/IL-18 (caspase-1) signaling; CD2–WASP–actin cytoskeletal signaling (immunological synapse formation); F-BAR-domain membrane remodeling/podosome regulation.

Cell types involved (candidate CL terms): - Neutrophils (CL:0000775) — pathergy, sterile arthritis/PG neutrophilic infiltrate - Macrophages (CL:0000235) — cytoskeletal/podosome dysfunction, IL-1β production - T lymphocytes (CL:0000084) — CD2/WASP synapse dysfunction - Synoviocytes/synovial fibroblasts — site of joint inflammation

Suggested GO terms: - GO:0043123 — positive regulation of canonical NF-kappaB signal transduction (downstream inflammatory signaling) - GO:0002534 — cytokine production involved in inflammatory response - GO:0097169 — AIM2 inflammasome complex assembly (analogous; pyrin inflammasome-specific GO term GO:0072559 "NLRP1 inflammasome complex" is not exact — best available may be the general "inflammasome complex" GO:0061702) - GO:0030041 — actin filament polymerization - GO:0002376 — immune system process (broad, for CD2/WASP synapse formation)

7. Anatomical Structures Affected

Organ level (primary): joints (elbows, knees, ankles predominant), skin (site of PG ulcers and acne).
Secondary: in the PAMI/PSTPIP1-spectrum extreme, reticuloendothelial system — hepatosplenomegaly, lymphadenopathy, bone marrow (cytopenias).
Body systems: musculoskeletal, integumentary, immune (innate).
Tissue/cell level: synovium (neutrophilic synovitis), dermis/epidermis (ulcerative pyoderma gangrenosum, pilosebaceous unit in acne).
Subcellular: cytoskeleton/cell cortex (F-BAR domain membrane deformation, filopodia/podosome structures), cytoplasmic inflammasome (ASC speck) assembly.
Candidate UBERON terms: UBERON:0000982 (synovial joint), UBERON:0002097 (skin of body), UBERON:0001004 (respiratory system - N/A here), UBERON:0002370 (thymus - N/A). Most relevant: UBERON:0000982 (joint), UBERON:0002097 (skin).
Laterality: typically unilateral/asymmetric during individual arthritis flares (migratory monoarticular pattern), though different joints affected over time.

8. Temporal Development

Onset: childhood, classically before age 10, sometimes as early as infancy for arthritis; cutaneous manifestations (PG, cystic acne) typically emerge later, around puberty/adolescence.
Pattern: episodic/relapsing-remitting for both arthritis and PG flares, often trauma-triggered (pathergy).
Progression: arthritis is most active in childhood/pre-puberty and tends to attenuate afterward; cutaneous disease (PG and severe acne) increases from puberty into adulthood — a documented "phenotypic switch" over the disease course (PMC3737487).
Duration: chronic, lifelong (though joint disease activity often diminishes with age; residual joint damage from earlier destructive flares may persist).
Critical periods: childhood/adolescence — periods of highest inflammatory activity, when early diagnosis and IL-1 blockade could in principle limit joint destruction and cutaneous scarring; this is inferred rather than demonstrated by controlled trial data given disease rarity.

9. Inheritance and Population

Epidemiology: exceptionally rare; prevalence <1 per 1,000,000. As of the WebSearch source cited, only ~34 patients from 5 kindreds (2 US, 1 Italian, 1 Dutch, 1 New Zealand) had been formally reported in the classic literature (WebSearch summary; see also Orphanet); subsequent case reports (including a 2026 Chinese family report) have added further cases but the total remains in the low hundreds worldwide across the full PSTPIP1-spectrum literature.
Inheritance pattern: autosomal dominant.
Penetrance: incomplete.
Expressivity: markedly variable, both between and within families (documented directly in the 5-patient genotype-phenotype study, PMC3737487).
Genetic anticipation: not reported/expected (not a repeat-expansion disorder).
Founder effects/consanguinity: not specifically reported for the classic PAPA-causing variants; several kindreds independently ascertained across different populations/geographies.
Genotype–phenotype spectrum note: the E250K (as opposed to classic E250Q) and E257K variants are specifically associated with the more severe PAMI phenotype (myeloid-related proteinemia, hyperzincemia/hypercalprotectinemia, cytopenias, failure to thrive) rather than classic PAPA — an important within-gene genotype-phenotype correlation to track separately in curation (PMC10454568; Sciencedirect phenotype-genotype paper/PubMed 33218716).
Sex ratio / geographic distribution: no strong sex predilection or endemic geographic clustering reported in the sources surveyed.

10. Diagnostics

Clinical/laboratory: - Synovial fluid analysis: exceedingly high, sterile neutrophilic cell counts (differentiates from true septic arthritis) — a key diagnostic discriminator emphasized in a dedicated case series (PubMed 28251506). - Elevated ESR/CRP during flares; elevated IL-1β; in PAMI-spectrum disease, markedly elevated serum zinc and calprotectin (S100A8/A9). - Imaging (radiographs, MRI, ultrasound) used to characterize joint destruction and differentiate from infectious/other inflammatory arthritis — reviewed specifically for PAPA in a Pediatric Radiology imaging-findings paper (Springer 2018). - Skin biopsy of PG lesions: neutrophilic dermatosis pattern (nonspecific but supportive).

Genetic testing: Single-gene sequencing of PSTPIP1 (Sanger or targeted NGS) is the diagnostic standard given the small number of known causal variants clustering in the coiled-coil domain; autoinflammatory-disease gene panels including PSTPIP1, MEFV, NLRP3, TNFRSF1A, MVK, etc. are commonly used given phenotypic overlap with other periodic fever/autoinflammatory syndromes.

Clinical criteria / differential diagnosis: No formal consensus diagnostic criteria akin to DSM/ICD were identified in this search; diagnosis remains clinical, supported by genetic confirmation. Key differentials: - Septic arthritis (ruled out by sterile cultures despite very high synovial WBC). - Pyoderma gangrenosum from other causes (IBD-associated, idiopathic). - PASH syndrome (Pyoderma gangrenosum, Acne, Suppurative Hidradenitis) — lacks the sterile pyogenic arthritis of PAPA; caused variably by PSTPIP1 variants or other/no identified gene (PubMed 21745697). - PAPASH (PAPA + hidradenitis suppurativa). - PsAPASH (PASH + psoriatic arthritis). - PASS syndrome (PG, acne, ankylosing spondylitis ± hidradenitis suppurativa). - PAC syndrome (PG, acne, ulcerative colitis). - PAMI syndrome (PSTPIP1-associated myeloid-related proteinemia inflammatory syndrome) — a more severe, often earlier-onset phenotype associated specifically with E250K/E257K, featuring failure to thrive, lymphadenopathy, splenomegaly, and cytopenias in addition to/preceding classic PAPA features. (Spectrum summarized in WebSearch synthesis of differential-diagnosis sources, including DermNet NZ.)

11. Outcome/Prognosis

No formal survival/mortality statistics are established — PAPA syndrome is not typically fatal, but morbidity from joint destruction and disfiguring cutaneous scarring can be substantial if untreated.
Morbidity: destructive arthropathy (if arthritis flares are inadequately controlled in childhood), disfiguring PG scarring, severe acne scarring.
Complications: secondary infection of ulcerated PG lesions; in PAMI-spectrum disease, cytopenias and growth failure add additional morbidity.
Prognostic factors: early recognition and IL-1 pathway blockade may limit long-term joint damage and scarring, though this is inferred from case-series treatment response data rather than controlled prognostic studies (disease too rare for such studies to exist).

12. Treatment

Pharmacotherapy — biologics targeting IL-1 and TNF pathways are the mainstay:

Anti-IL-1 agents (anakinra, canakinumab): most effective for the arthritis component; markedly lower efficacy against PG and acne according to a 2025 systematic review of 10 case-report studies (19 patients total) (Springer Nature, Archives of Dermatological Research 2025). Canakinumab (dosed every 4-8 weeks) shows better compliance and fewer injection-site reactions than daily anakinra, though head-to-head comparative data remain limited; both are used, but the review explicitly calls for RCTs given the current evidence base is limited to small case series.
Anti-TNF agents (etanercept, adalimumab, infliximab, golimumab): also reported effective, with some evidence that infliximab or high-dose golimumab may outperform etanercept/adalimumab for severe PG lesions specifically (WebSearch synthesis; foundational case report: PubMed 15580218, abnormal TNF-α production and etanercept efficacy; Use of TNF inhibitors in PAPA syndrome, PMC4599379).
Combination anti-TNF + anti-IL-1 therapy: used for cases refractory to monotherapy with either class, reported as more effective than escalating corticosteroids (WebSearch synthesis of combination-therapy case reports).
Corticosteroids (systemic and intralesional/intra-articular): used historically and still commonly as adjunct/bridge therapy, though associated with significant toxicity with prolonged use.

Suggested NCIT terms: - NCIT:C15986 (Pharmacotherapy) — generic action - Anakinra: therapeutic_agent candidate (NCIT has an "Anakinra" concept; verify exact CURIE via OAK before curation — not independently confirmed in this search pass) - Canakinumab, Infliximab, Etanercept, Adalimumab — likewise verify exact NCIT CURIEs at curation time - NCIT:C2874 (Corticosteroid) class-level term as an alternative/adjunct

Surgical/supportive: avoidance of unnecessary surgical intervention/injections given pathergy risk; wound care for PG ulcers; dermatologic management of acne (isotretinoin reported in some case series, though can be associated with flares in some autoinflammatory-adjacent conditions — verify per-case before curating as a general recommendation).

Experimental/emerging: No PAPA-syndrome-specific registered clinical trials (NCT) were identified in this search pass; given the disease's rarity, most treatment evidence is derived from off-label biologic use documented in case reports/series rather than formal trials — this should be flagged as an evidence gap when curating clinical_trials.

13. Prevention

No primary prevention exists for this monogenic dominant disorder beyond genetic counseling for at-risk family members (each child of an affected parent has ~50% inheritance risk, subject to incomplete penetrance).
Secondary/tertiary prevention: the central actionable preventive strategy documented in the literature is avoidance of unnecessary trauma/injections to minimize pathergy-triggered flares, plus early initiation of IL-1/TNF-targeted therapy to prevent cumulative joint destruction and cutaneous scarring.
Genetic counseling: appropriate given autosomal dominant inheritance with variable expressivity; prenatal/preimplantation testing is technically feasible via single-gene PSTPIP1 testing but is not routinely reported as clinical practice for this non-lethal, treatable disorder.

14. Other Species / Natural Disease

No naturally occurring veterinary/companion-animal PAPA-syndrome-equivalent disease was identified in this search (searches for OMIA-style veterinary correlates did not surface a distinct entry); this should be recorded as absent/not identified rather than assumed absent.
Comparative biology is instead addressed through engineered mouse models (below) rather than naturally occurring animal disease.

15. Model Organisms

Genetic mouse model — A230T knock-in/ectopic expression: - Mice ectopically/ubiquitously expressing human PAPA-associated PSTPIP1 A230T were not born at expected Mendelian ratios, and surviving mice showed growth retardation and elevated circulating proinflammatory cytokines (PMC3576065). - Critically, despite elevated circulating cytokines "implicated in active pyoderma gangrenosum," these mice failed to develop the specific skin inflammation and arthritis phenotype seen in human PAPA syndrome (PMC3576065) — this is a HUMAN_MODEL_MISMATCH-type finding per this repository's convention: systemic cytokine dysregulation is recapitulated, but organ-specific lesion formation (joint/skin) is not, suggesting the mouse model captures the inflammasome/cytokine arm of pathogenesis but misses species-specific or context-dependent factors required for the human tissue phenotype (see mechanism §6, step 7-8 caveat). - In vitro cellular studies (non-animal) additionally show that PAPA-mutant A230T increases IL-1β secretion relative to wild-type PSTPIP1 in cell-based assays, consistent with — but independently supporting — the mouse cytokine findings ([WebSearch synthesis of PMC3576065 discussion]).

Related model systems (mechanistic, not disease-specific): - PSTPIP2 (a paralog) knockout/mutant mice (e.g., the classic "cmo" chronic multifocal osteomyelitis mouse) are widely used to study PSTPIP-family adaptor biology in neutrophil-mediated autoinflammation, though PSTPIP2 is genetically and phenotypically distinct from PSTPIP1/PAPA and should not be conflated with a PAPA model per se (PMC9807597). - A separate murine model of pyoderma gangrenosum (not PSTPIP1-based) implicating IL-1β-primed neutrophils and skin-gut crosstalk exists in the literature and may be useful as a mechanistic (not genetic) comparator for the PG component of the PAPA phenotype (Frontiers Immunology 2023).

Model limitations: the existing A230T mouse model recapitulates the biochemical/cytokine axis of disease but not the defining clinical lesions (arthritis, PG), representing a significant translational gap between the demonstrated pyrin-inflammasome/IL-1β mechanism and the tissue-specific human phenotype — an important caveat for any mechanistic module curation that cites this model as supporting evidence for the joint/skin nodes specifically (as opposed to the cytokine-production node).

Summary of Key Ontology Term Candidates for Curation

Concept	Suggested term
Disease	MONDO:0011462; OMIM:604416; ORPHA:69126
Gene	hgnc:9581 (PSTPIP1)
Modifier gene/pathway partner	MEFV (pyrin)
Sterile pyogenic arthritis	HP term for arthritis (verify exact HP CURIE at curation — general HP:0001369 Arthritis, or more specific sterile/pyogenic arthritis term if one exists)
Pyoderma gangrenosum	HP:0031928 (verify exact match)
Cystic acne	HP-subtree acne term (verify exact match)
Pathergy	verify HP term availability
Inflammasome activation	GO:0061702 (inflammasome complex) or more specific pyrin-inflammasome GO term (verify)
Actin cytoskeleton regulation	GO:0030041 (actin filament polymerization)
Neutrophil	CL:0000775
Synovial joint	UBERON:0000982
Skin	UBERON:0002097
Anakinra/Canakinumab (treatment)	NCIT — verify exact CURIEs via OAK

Note on evidence gaps to flag during curation: (1) no RCT-level treatment data exist — all treatment evidence is case-report/series level; (2) the mouse model shows a human-model mismatch for the tissue-specific (joint/skin) phenotype despite recapitulating the cytokine phenotype; (3) QoL-instrument data (EQ-5D/SF-36) specific to PAPA syndrome were not located in this search pass and may not exist in the primary literature; (4) exact PMIDs for several foundational papers (Wise 2002, Shoham/PNAS pyrin-PSTPIP1 paper, Lindor 1997) should be independently verified and fetched via just fetch-reference before use as KB evidence, since this report's citations came from web search summaries rather than direct PMID lookup for every source.

Sources: - PSTPIP1-Associated Myeloid-Related Proteinemia Inflammatory (PAMI) Syndrome: A Systematic Review - PMC - A de novo heterozygous PSTPIP1 variant associated with PAPA syndrome: Chinese case report and review - Frontiers Genetics - PAPA Syndrome - ScienceDirect Topics overview - A novel pathogenic variant in PSTPIP1 highlights the diversity of PSTPIP1-associated disorders - Rheumatology/Oxford Academic - Phenotypic Associations of PSTPIP1 Sequence Variants - PubMed 33218716 - PAPA syndrome - Wikidata (OMIM/Orphanet/MONDO IDs) - Orphanet: PAPA syndrome (ORPHA:69126) - Pyrin Modulates the Intracellular Distribution of PSTPIP1 - PMC2702820 - Inflammation in Mice Ectopically Expressing PSTPIP1 A230T - PMC3576065 - Pyrin binds the PSTPIP1/CD2BP1 protein - PNAS - The role of anti-IL-1 drugs in the treatment of PAPA syndrome: a systematic review - Arch Dermatol Res 2025 - Anakinra in PAPASH Spectrum Disorder: Case Report - PMC11244945 - OMIM 604416 - PYOGENIC STERILE ARTHRITIS, PYODERMA GANGRENOSUM, AND ACNE - Genotype, Phenotype, and Clinical Course in Five Patients With PAPA Syndrome - PMC3737487 - Pyogenic arthritis, pyoderma gangrenosum, and acne syndrome in a Chinese family - PMC8362586 - Imaging findings of PAPA syndrome: differential diagnosis - Pediatric Radiology 2018 - PAPA syndrome: differential diagnosis by synovial cell counts - PubMed 28251506 - Pyoderma gangrenosum, acne, and suppurative hidradenitis (PASH) - PubMed 21745697 - PAPA syndrome - DermNet NZ - Mutations in CD2BP1 disrupt binding to PTP PEST and are responsible for PAPA syndrome - Human Molecular Genetics (Wise et al. 2002) - Clinical, Molecular, and Genetic Characteristics of PAPA Syndrome: A Review - PMC3048314 - Abnormal TNF-α production and etanercept efficacy in PAPA syndrome - PubMed 15580218 - Use of TNF inhibitors in the treatment of PAPA syndrome - PMC4599379 - Combination TNF and IL-1 blockade in PAPA syndrome - PMC3952270 - WASp acts downstream of CD2 and CD2AP/PSTPIP1 adaptors - PubMed 12530983 - The F-BAR protein PSTPIP1 controls ECM degradation and filopodia formation in macrophages - Blood/ASH - Molecular interactions of adaptor protein PSTPIP2 in neutrophil-mediated autoinflammation - PMC9807597 - A novel murine model of pyoderma gangrenosum - Frontiers Immunology 2023

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Deep Research

1. Disease Information

2. Etiology

3. Phenotypes

Articular

Cutaneous

Laboratory abnormalities

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Ontology Term Candidates for Curation