Schnitzler Syndrome

Complex MONDO:0018304 Pathograph 2 Show in embeddings browser autoinflammatory syndrome rare disease

Schnitzler syndrome is a rare, acquired adult-onset autoinflammatory disorder defined by the combination of a chronic urticarial rash and a monoclonal IgM (more rarely IgG) gammopathy, accompanied by signs of systemic inflammation: recurrent fever, bone pain, arthralgia/arthritis, lymphadenopathy, and markedly elevated acute-phase reactants. It shares strong clinicopathologic similarities with monogenic IL-1-mediated autoinflammatory disorders and is driven by dysregulated interleukin-1 (in particular IL-1 beta) signaling, as demonstrated by the dramatic response to IL-1 blockade. The disorder is sporadic, has no germline Mendelian cause, and carries an increased long-term risk of evolution to a lymphoproliferative disorder, most often Waldenstrom macroglobulinemia.

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3
Pathophys.
13
Phenotypes
2
Gaps
2
Pathograph
1
Genes
2
Medical Actions
2
Differentials
1
Trials
6
References
1
Deep Research
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Discussions and Knowledge Gaps

2
Why is there no validated animal or genetic model of Schnitzler syndrome, and how does this limit mechanistic study?
KNOWLEDGE GAP OPEN gap_schnitzler_no_model
Attached to
pathophysiology#IL-1 Driven Autoinflammation
Schnitzler syndrome is an acquired, sporadic disorder tied to an aging human clonal/innate-immune context with no germline Mendelian cause, and has not been recapitulated in a model organism; mechanistic insight derives almost entirely from human clinical and ex vivo studies.
Show evidence (1 reference)
PMID:38927050 SUPPORT Human Clinical
"the physiopathology of Schnitzler syndrome remains elusive"
The physiopathology remains elusive, consistent with the absence of a validated disease model.
⚙

Pathophysiology

3
IL-1 Driven Autoinflammation
Schnitzler syndrome is now regarded as an acquired adult-onset autoinflammatory disease in which dysregulated innate immunity drives systemic inflammation. Interleukin-1 (especially IL-1 beta) is the pivotal mediator; the near-pathognomonic response to IL-1 inhibitors demonstrates the central role of this cytokine in disease pathogenesis.
monocyte CL:0000576 macrophage CL:0000235 neutrophil CL:0000775
Interleukin-1-mediated signaling GO:0070498 ↑ INCREASED Interleukin-1 beta production GO:0032611 ↑ INCREASED
Downstream
Systemic Inflammatory Response IL-1-driven autoinflammation produces the systemic inflammatory response (fever, arthralgia, bone pain, acute-phase reactant elevation).
Show evidence (3 references)
PMID:38927050 SUPPORT Human Clinical
"Schnitzler syndrome shares strong clinicopathologic similarities with monogenic IL-1-mediated autoinflammatory disorders and is now considered an acquired adult-onset autoinflammatory disease."
Establishes Schnitzler syndrome as an acquired adult-onset autoinflammatory disease related to IL-1-mediated autoinflammation.
PMID:38927050 SUPPORT Human Clinical
"The spectacular effect of interleukin-1 inhibitors demonstrates the key role of this cytokine in the pathogenesis of the disease."
The response to IL-1 inhibitors demonstrates the central pathogenic role of interleukin-1.
PMID:25905009 SUPPORT Human Clinical
"the pivotal role of interleukin-1 beta in this disorder"
Identifies IL-1 beta as the pivotal cytokine in Schnitzler syndrome.
Systemic Inflammatory Response
Sustained IL-1-driven inflammation produces a chronic systemic inflammatory state with fever, arthralgia, bone pain, and markedly elevated acute-phase reactants (CRP, serum amyloid A). This is the clinical readout of the autoinflammatory cascade and the target of disease-activity monitoring.
Inflammatory response GO:0006954 ↑ INCREASED
Show evidence (1 reference)
PMID:25905009 SUPPORT Human Clinical
"signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
Describes the systemic inflammatory features that define the clinical syndrome.
Monoclonal Gammopathy
A monoclonal IgM (rarely IgG) gammopathy is a mandatory feature of Schnitzler syndrome, reflecting an underlying clonal B-cell/plasma-cell process. The relationship between the monoclonal component and the autoinflammation is not fully understood, but a shared pathophysiologic mechanism is hypothesized, and the clonal process underlies the long-term risk of lymphoproliferative transformation.
plasma cell CL:0000786
Show evidence (2 references)
PMID:31228950 SUPPORT Human Clinical
"Schnitzler's syndrome is an auto-inflammatory disorder which is characterized by two mandatory features: an urticarial rash and a monoclonal gammopathy."
Establishes the monoclonal gammopathy as one of the two mandatory defining features of the syndrome.
PMID:31228950 PARTIAL Human Clinical
"a mutual factor in pathophysiology however seems likely"
Supports the hypothesis that the autoinflammation and the monoclonal gammopathy share a common pathophysiologic mechanism, though the link is not yet elucidated.
⬡

Pathograph

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

Phenotypes

13
Cardiovascular 3
Chronic Urticarial Rash Urticaria HP:0001025
Temporal: CHRONIC
Show evidence (1 reference)
PMID:25905009 SUPPORT Human Clinical
"the association of a monoclonal IgM (or IgG) gammopathy, a chronic urticarial rash, and signs and symptoms of systemic inflammation"
The chronic urticarial rash is one of the defining associations of Schnitzler syndrome.
Lymphadenopathy Lymphadenopathy HP:0002716
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"Lymphadenopathy was detected in 6 (35.3%) patients"
Lymphadenopathy occurred in 35.3% of patients in a multicenter cohort.
Pericarditis Pericarditis HP:0001701
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"pericarditis, in 4 (23.5%)"
Pericarditis occurred in 23.5% of patients in a multicenter cohort.
Digestive 1
Hepatomegaly Hepatomegaly HP:0002240
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"enlarged liver, in 6 (35.3%)"
Hepatomegaly occurred in 35.3% of patients in a multicenter cohort.
Metabolism 1
Recurrent Fever Recurrent fever HP:0001954
Temporal: RECURRENT
Show evidence (2 references)
PMID:25905009 SUPPORT Human Clinical
"signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
Fever is listed among the systemic inflammatory features of the syndrome.
PMID:38861148 SUPPORT Human Clinical
"Clinical manifestations of the disease in all patients included fatigue, lethargy, fatigue, rash, and fever."
Fever was a clinical manifestation in all patients in the cohort.
Musculoskeletal 1
Arthritis Arthritis HP:0001369
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"arthritis, in 9 (52.9%)"
Arthritis occurred in 52.9% of patients in a multicenter cohort.
Constitutional 4
Bone Pain Bone pain HP:0002653
Show evidence (2 references)
PMID:25905009 SUPPORT Human Clinical
"signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
Bone pain is one of the systemic inflammatory features of the syndrome.
PMID:38861148 SUPPORT Human Clinical
"Bone pain was observed in 12 (70.6%) patients"
Bone pain occurred in 70.6% of patients in a multicenter cohort.
Arthralgia Arthralgia HP:0002829
Show evidence (2 references)
PMID:25905009 SUPPORT Human Clinical
"signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
Arthralgia is one of the systemic inflammatory features of the syndrome.
PMID:38861148 SUPPORT Human Clinical
"arthralgias, in 16 (94.1%)"
Arthralgia occurred in 94.1% of patients in a multicenter cohort.
Myalgia Myalgia HP:0003326
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"myalgia, in 7 (41.2%)"
Myalgia occurred in 41.2% of patients in a multicenter cohort.
Fatigue Fatigue HP:0012378
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"Clinical manifestations of the disease in all patients included fatigue, lethargy, fatigue, rash, and fever."
Fatigue was a clinical manifestation in all patients in the cohort.
Growth 1
Weight Loss Weight loss HP:0001824
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"weight loss, in 4 (23.5%)"
Weight loss occurred in 23.5% of patients in a multicenter cohort.
Other 2
Monoclonal IgM Gammopathy IgM heavy chain paraproteinemia HP:0020196
Show evidence (2 references)
PMID:25905009 SUPPORT Human Clinical
"the association of a monoclonal IgM (or IgG) gammopathy"
A monoclonal IgM (or IgG) gammopathy is part of the defining association of Schnitzler syndrome.
PMID:38861148 SUPPORT Human Clinical
"Monoclonal gammopathy was detected in all patients with a secretion level of 2.9-15.1 g/L: IgMk (n = 10, 64.7%)"
In a 17-patient cohort, monoclonal gammopathy was present in all, most commonly IgM kappa.
Elevated Acute-Phase Reactants Elevated circulating C-reactive protein concentration HP:0011227
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"All patients had an increased level of ESR and CRP."
All patients in the cohort had elevated ESR and CRP.
🧬

Genetic Associations

1
MYD88 (somatic, hypothesized)
Gene: MYD88 hgnc:7562 variant_origin: SOMATIC
Show evidence (1 reference)
PMID:31228950 PARTIAL Human Clinical
"Here we present a novel hypothesis of a shared pathophysiologic mechanism between Schitzler's syndrome and monoclonal gammopathy."
Supports the hypothesized shared (MYD88-related) mechanism between Schnitzler syndrome and the monoclonal gammopathy / Waldenstrom disease, flagged as a hypothesis rather than an established causal variant.
💊

Medical Actions

2
Anakinra (IL-1 Receptor Antagonist)
Category: Therapeutic Action: Pharmacotherapy NCIT:C15986
Agent: anakinra CHEBI:231683
Anakinra is a recombinant IL-1 receptor antagonist that blocks both IL-1 alpha and IL-1 beta. It is a very effective treatment for Schnitzler syndrome, producing rapid clinical remission, but requires daily subcutaneous injection and symptoms recur shortly after stopping.
Show evidence (1 reference)
PMID:23087179 SUPPORT Human Clinical
"The interleukin (IL) 1 receptor antagonist anakinra is a very effective treatment, but requires daily injection and blocks both IL-1α and IL-1β."
Anakinra (an IL-1 receptor antagonist) is a very effective treatment for Schnitzler syndrome.
Canakinumab (Anti-IL-1beta Monoclonal Antibody)
Category: Therapeutic Action: Pharmacotherapy NCIT:C15986
Agent: canakinumab NCIT:C80971
Canakinumab is a selective human monoclonal anti-IL-1 beta antibody with a long half-life allowing monthly dosing. A randomized placebo-controlled study demonstrated efficacy, with significant improvement in clinical signs, inflammatory markers, and quality of life. It is effective in anakinra-treated patients and is a key targeted therapy.
Show evidence (2 references)
PMID:27658762 SUPPORT Human Clinical
"The proportion of patients with complete clinical response at day 7 was significantly higher (P = .001) in the canakinumab-treated group (n = 5 of 7) than in the placebo group (n = 0 of 13)."
In a randomized placebo-controlled study, canakinumab produced significantly higher complete clinical response than placebo.
PMID:23087179 SUPPORT Human Clinical
"Canakinumab induced complete or clinical remission at day 14 in all eight patients."
Canakinumab induced complete or clinical remission in all patients of a 9-month open-label trial.
🔬

Biochemical Markers

2
Monoclonal IgM Paraprotein
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"Monoclonal gammopathy was detected in all patients with a secretion level of 2.9-15.1 g/L: IgMk (n = 10, 64.7%)"
Documents the monoclonal IgM paraprotein, predominantly IgM kappa, in all cohort patients.
Elevated CRP and ESR
Show evidence (1 reference)
PMID:23087179 SUPPORT Human Clinical
"Median C-reactive protein concentrations decreased from 169 mg/l at baseline to less than 10 mg/l on day 14"
Markedly elevated baseline CRP (median 169 mg/L) that normalizes on treatment, confirming CRP as an activity biomarker.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Schnitzler Syndrome:

Cryopyrin-Associated Periodic Syndrome (CAPS)
Overlapping Features CAPS and other monogenic autoinflammatory diseases with urticarial rash can mimic Schnitzler syndrome but are typically childhood-onset, hereditary, and lack a monoclonal gammopathy; they must be excluded.
Distinguishing Features
  • Germline NLRP3 mutation and earlier (often childhood) onset in CAPS
  • Absence of monoclonal gammopathy in CAPS
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"monogenic AIDs (CAPS, TRAPS, and HIDS) were excluded from all patients at the prehospital stage"
Monogenic autoinflammatory diseases including CAPS are excluded when diagnosing Schnitzler syndrome.
Lymphoproliferative Disorder (Waldenstrom Macroglobulinemia)
Overlapping Features An overt lymphoproliferative disorder, particularly Waldenstrom macroglobulinemia, can present with a monoclonal IgM and must be distinguished; Schnitzler syndrome carries an increased long-term risk of transformation to such disorders.
Distinguishing Features
  • Overt clonal lymphoplasmacytic infiltrate/tissue diagnosis in malignancy
  • Schnitzler syndrome adds the chronic urticarial autoinflammatory phenotype
Show evidence (1 reference)
PMID:38861148 SUPPORT Human Clinical
"Infectious and lymphoproliferative diseases, monogenic AIDs (CAPS, TRAPS, and HIDS) were excluded from all patients at the prehospital stage."
Lymphoproliferative disease must be excluded when establishing the diagnosis.
🔬

Clinical Trials

1
NCT01276522 NOT_APPLICABLE COMPLETED
Open-label, single-treatment-arm study of monthly subcutaneous canakinumab (150 or 300 mg) in patients with active Schnitzler syndrome, assessing the efficacy and safety of selective IL-1 beta blockade. Results reported in PMID:23087179.
Target Phenotypes: Urticaria HP:0001025 Recurrent fever HP:0001954
Show evidence (1 reference)
clinicaltrials:NCT01276522 SUPPORT Human Clinical
"This is a 6-month open-label, single treatment arm study of canakinumab 150 or 300 mg (in case of insufficient response to 150 mg) subcutaneous injection once per month in patients with active Schnitzler syndrome, in which efficacy and safety will be assessed."
Trial evaluated monthly canakinumab (IL-1 beta blockade) for efficacy and safety in active Schnitzler syndrome.
{ }

Source YAML

click to show 
name: Schnitzler Syndrome
creation_date: "2026-06-29T00:00:00Z"
category: Complex
disease_term:
  preferred_term: Schnitzler syndrome
  term:
    id: MONDO:0018304
    label: Schnitzler syndrome
parents:
  - autoinflammatory syndrome
  - rare disease
synonyms:
  - Schnitzler's syndrome
  - chronic urticaria with gammopathy
  - chronic urticaria with macroglobulinemia
description: >
  Schnitzler syndrome is a rare, acquired adult-onset autoinflammatory disorder
  defined by the combination of a chronic urticarial rash and a monoclonal IgM
  (more rarely IgG) gammopathy, accompanied by signs of systemic inflammation:
  recurrent fever, bone pain, arthralgia/arthritis, lymphadenopathy, and markedly
  elevated acute-phase reactants. It shares strong clinicopathologic similarities
  with monogenic IL-1-mediated autoinflammatory disorders and is driven by
  dysregulated interleukin-1 (in particular IL-1 beta) signaling, as demonstrated
  by the dramatic response to IL-1 blockade. The disorder is sporadic, has no
  germline Mendelian cause, and carries an increased long-term risk of evolution
  to a lymphoproliferative disorder, most often Waldenstrom macroglobulinemia.
pathophysiology:
- name: IL-1 Driven Autoinflammation
  description: >
    Schnitzler syndrome is now regarded as an acquired adult-onset
    autoinflammatory disease in which dysregulated innate immunity drives systemic
    inflammation. Interleukin-1 (especially IL-1 beta) is the pivotal mediator;
    the near-pathognomonic response to IL-1 inhibitors demonstrates the central
    role of this cytokine in disease pathogenesis.
  cell_types:
  - preferred_term: monocyte
    term:
      id: CL:0000576
      label: monocyte
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: Interleukin-1-mediated signaling
    term:
      id: GO:0070498
      label: interleukin-1-mediated signaling pathway
    modifier: INCREASED
  - preferred_term: Interleukin-1 beta production
    term:
      id: GO:0032611
      label: interleukin-1 beta production
    modifier: INCREASED
  evidence:
  - reference: PMID:38927050
    reference_title: "Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Schnitzler syndrome shares strong clinicopathologic similarities with monogenic IL-1-mediated autoinflammatory disorders and is now considered an acquired adult-onset autoinflammatory disease."
    explanation: >-
      Establishes Schnitzler syndrome as an acquired adult-onset autoinflammatory
      disease related to IL-1-mediated autoinflammation.
  - reference: PMID:38927050
    reference_title: "Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The spectacular effect of interleukin-1 inhibitors demonstrates the key role of this cytokine in the pathogenesis of the disease."
    explanation: >-
      The response to IL-1 inhibitors demonstrates the central pathogenic role of
      interleukin-1.
  - reference: PMID:25905009
    reference_title: "Schnitzler's syndrome: lessons from 281 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the pivotal role of interleukin-1 beta in this disorder"
    explanation: >-
      Identifies IL-1 beta as the pivotal cytokine in Schnitzler syndrome.
  downstream:
  - target: Systemic Inflammatory Response
    causal_link_type: DIRECT
    description: >-
      IL-1-driven autoinflammation produces the systemic inflammatory response
      (fever, arthralgia, bone pain, acute-phase reactant elevation).
    evidence:
    - reference: PMID:25905009
      reference_title: "Schnitzler's syndrome: lessons from 281 cases."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
      explanation: >-
        Links the autoinflammatory process to the systemic inflammatory
        manifestations of the syndrome.
- name: Systemic Inflammatory Response
  description: >
    Sustained IL-1-driven inflammation produces a chronic systemic inflammatory
    state with fever, arthralgia, bone pain, and markedly elevated acute-phase
    reactants (CRP, serum amyloid A). This is the clinical readout of the
    autoinflammatory cascade and the target of disease-activity monitoring.
  biological_processes:
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  evidence:
  - reference: PMID:25905009
    reference_title: "Schnitzler's syndrome: lessons from 281 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
    explanation: >-
      Describes the systemic inflammatory features that define the clinical
      syndrome.
- name: Monoclonal Gammopathy
  description: >
    A monoclonal IgM (rarely IgG) gammopathy is a mandatory feature of Schnitzler
    syndrome, reflecting an underlying clonal B-cell/plasma-cell process. The
    relationship between the monoclonal component and the autoinflammation is not
    fully understood, but a shared pathophysiologic mechanism is hypothesized, and
    the clonal process underlies the long-term risk of lymphoproliferative
    transformation.
  cell_types:
  - preferred_term: plasma cell
    term:
      id: CL:0000786
      label: plasma cell
  evidence:
  - reference: PMID:31228950
    reference_title: "Schnitzler's syndrome - a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Schnitzler's syndrome is an auto-inflammatory disorder which is characterized by two mandatory features: an urticarial rash and a monoclonal gammopathy."
    explanation: >-
      Establishes the monoclonal gammopathy as one of the two mandatory defining
      features of the syndrome.
  - reference: PMID:31228950
    reference_title: "Schnitzler's syndrome - a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "a mutual factor in pathophysiology however seems likely"
    explanation: >-
      Supports the hypothesis that the autoinflammation and the monoclonal
      gammopathy share a common pathophysiologic mechanism, though the link is
      not yet elucidated.
phenotypes:
- category: Dermatologic
  name: Chronic Urticarial Rash
  description: >
    A chronic urticarial rash (neutrophilic urticarial dermatosis) is an obligate
    defining feature, typically present in essentially all patients. It is often
    the first manifestation of the disease.
  phenotype_term:
    preferred_term: Urticaria
    term:
      id: HP:0001025
      label: Urticaria
    temporality: CHRONIC
  evidence:
  - reference: PMID:25905009
    reference_title: "Schnitzler's syndrome: lessons from 281 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the association of a monoclonal IgM (or IgG) gammopathy, a chronic urticarial rash, and signs and symptoms of systemic inflammation"
    explanation: >-
      The chronic urticarial rash is one of the defining associations of
      Schnitzler syndrome.
- category: Immunologic
  name: Monoclonal IgM Gammopathy
  description: >
    A monoclonal IgM gammopathy (more rarely IgG) is a mandatory diagnostic
    feature. IgM kappa is the most common isotype. In a multicenter cohort,
    monoclonal gammopathy was detected in all patients, most often IgM kappa.
  phenotype_term:
    preferred_term: IgM heavy chain paraproteinemia
    term:
      id: HP:0020196
      label: IgM heavy chain paraproteinemia
  evidence:
  - reference: PMID:25905009
    reference_title: "Schnitzler's syndrome: lessons from 281 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the association of a monoclonal IgM (or IgG) gammopathy"
    explanation: >-
      A monoclonal IgM (or IgG) gammopathy is part of the defining association of
      Schnitzler syndrome.
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Monoclonal gammopathy was detected in all patients with a secretion level of 2.9-15.1 g/L: IgMk (n = 10, 64.7%)"
    explanation: >-
      In a 17-patient cohort, monoclonal gammopathy was present in all, most
      commonly IgM kappa.
- category: Constitutional
  name: Recurrent Fever
  description: >
    Recurrent/intermittent fever is a frequent systemic feature and a minor
    diagnostic criterion. It was reported in essentially all patients in a
    multicenter cohort.
  phenotype_term:
    preferred_term: Recurrent fever
    term:
      id: HP:0001954
      label: Recurrent fever
    temporality: RECURRENT
  evidence:
  - reference: PMID:25905009
    reference_title: "Schnitzler's syndrome: lessons from 281 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
    explanation: >-
      Fever is listed among the systemic inflammatory features of the syndrome.
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical manifestations of the disease in all patients included fatigue, lethargy, fatigue, rash, and fever."
    explanation: >-
      Fever was a clinical manifestation in all patients in the cohort.
- category: Skeletal
  name: Bone Pain
  description: >
    Bone pain (often in the lower limbs, associated with abnormal bone
    remodeling/osteosclerosis) is a characteristic feature and a minor diagnostic
    criterion. It was present in roughly 70% of a multicenter cohort.
  phenotype_term:
    preferred_term: Bone pain
    term:
      id: HP:0002653
      label: Bone pain
  evidence:
  - reference: PMID:25905009
    reference_title: "Schnitzler's syndrome: lessons from 281 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
    explanation: >-
      Bone pain is one of the systemic inflammatory features of the syndrome.
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bone pain was observed in 12 (70.6%) patients"
    explanation: >-
      Bone pain occurred in 70.6% of patients in a multicenter cohort.
- category: Musculoskeletal
  name: Arthralgia
  description: >
    Joint pain (arthralgia), with or without frank arthritis, is among the most
    frequent manifestations; it was present in over 90% of a multicenter cohort.
  phenotype_term:
    preferred_term: Arthralgia
    term:
      id: HP:0002829
      label: Arthralgia
  evidence:
  - reference: PMID:25905009
    reference_title: "Schnitzler's syndrome: lessons from 281 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "signs and symptoms of systemic inflammation, including fever, arthralgias and bone pain"
    explanation: >-
      Arthralgia is one of the systemic inflammatory features of the syndrome.
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "arthralgias, in 16 (94.1%)"
    explanation: >-
      Arthralgia occurred in 94.1% of patients in a multicenter cohort.
- category: Musculoskeletal
  name: Arthritis
  description: >
    Frank (non-erosive) arthritis occurs in a substantial minority of patients;
    it was present in about half of a multicenter cohort.
  phenotype_term:
    preferred_term: Arthritis
    term:
      id: HP:0001369
      label: Arthritis
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "arthritis, in 9 (52.9%)"
    explanation: >-
      Arthritis occurred in 52.9% of patients in a multicenter cohort.
- category: Musculoskeletal
  name: Myalgia
  description: >
    Muscle pain is a common systemic symptom accompanying flares.
  phenotype_term:
    preferred_term: Myalgia
    term:
      id: HP:0003326
      label: Myalgia
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "myalgia, in 7 (41.2%)"
    explanation: >-
      Myalgia occurred in 41.2% of patients in a multicenter cohort.
- category: Hematologic
  name: Lymphadenopathy
  description: >
    Reactive lymphadenopathy reflects the systemic inflammatory and clonal
    lymphoproliferative dimension of the disease.
  phenotype_term:
    preferred_term: Lymphadenopathy
    term:
      id: HP:0002716
      label: Lymphadenopathy
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Lymphadenopathy was detected in 6 (35.3%) patients"
    explanation: >-
      Lymphadenopathy occurred in 35.3% of patients in a multicenter cohort.
- category: Abdominal
  name: Hepatomegaly
  description: >
    Hepatic enlargement reflects reticuloendothelial involvement in a minority of
    patients.
  phenotype_term:
    preferred_term: Hepatomegaly
    term:
      id: HP:0002240
      label: Hepatomegaly
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "enlarged liver, in 6 (35.3%)"
    explanation: >-
      Hepatomegaly occurred in 35.3% of patients in a multicenter cohort.
- category: Constitutional
  name: Fatigue
  description: >
    Chronic fatigue/asthenia is a near-universal symptom that substantially
    impairs quality of life before treatment.
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical manifestations of the disease in all patients included fatigue, lethargy, fatigue, rash, and fever."
    explanation: >-
      Fatigue was a clinical manifestation in all patients in the cohort.
- category: Constitutional
  name: Weight Loss
  description: >
    Constitutional weight loss occurs in a minority of patients as part of the
    systemic inflammatory burden.
  phenotype_term:
    preferred_term: Weight loss
    term:
      id: HP:0001824
      label: Weight loss
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "weight loss, in 4 (23.5%)"
    explanation: >-
      Weight loss occurred in 23.5% of patients in a multicenter cohort.
- category: Cardiovascular
  name: Pericarditis
  description: >
    Serositis, presenting as pericarditis, occurs in a minority of patients as a
    systemic inflammatory manifestation.
  phenotype_term:
    preferred_term: Pericarditis
    term:
      id: HP:0001701
      label: Pericarditis
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pericarditis, in 4 (23.5%)"
    explanation: >-
      Pericarditis occurred in 23.5% of patients in a multicenter cohort.
- category: Laboratory
  name: Elevated Acute-Phase Reactants
  description: >
    Markedly elevated erythrocyte sedimentation rate and C-reactive protein are
    near-universal and track disease activity and treatment response.
  phenotype_term:
    preferred_term: Elevated circulating C-reactive protein concentration
    term:
      id: HP:0011227
      label: Elevated circulating C-reactive protein concentration
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had an increased level of ESR and CRP."
    explanation: >-
      All patients in the cohort had elevated ESR and CRP.
biochemical:
- name: Monoclonal IgM Paraprotein
  notes: >-
    A monoclonal IgM (rarely IgG) component on serum protein electrophoresis with
    immunofixation is a mandatory laboratory feature, usually low-level and most
    commonly IgM kappa.
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Monoclonal gammopathy was detected in all patients with a secretion level of 2.9-15.1 g/L: IgMk (n = 10, 64.7%)"
    explanation: >-
      Documents the monoclonal IgM paraprotein, predominantly IgM kappa, in all
      cohort patients.
- name: Elevated CRP and ESR
  notes: >-
    C-reactive protein and erythrocyte sedimentation rate are markedly elevated in
    active disease and normalize with effective IL-1 blockade, serving as
    disease-activity biomarkers.
  evidence:
  - reference: PMID:23087179
    reference_title: "Sustained efficacy of the monoclonal anti-interleukin-1 beta antibody canakinumab in a 9-month trial in Schnitzler's syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Median C-reactive protein concentrations decreased from 169 mg/l at baseline to less than 10 mg/l on day 14"
    explanation: >-
      Markedly elevated baseline CRP (median 169 mg/L) that normalizes on
      treatment, confirming CRP as an activity biomarker.
genetic:
- name: MYD88 (somatic, hypothesized)
  gene_term:
    preferred_term: MYD88
    term:
      id: hgnc:7562
      label: MYD88
  variant_origin: SOMATIC
  notes: >-
    Schnitzler syndrome is acquired and sporadic, with no germline Mendelian
    cause. A shared pathophysiologic mechanism with Waldenstrom macroglobulinemia
    has been hypothesized, in which the recurrent somatic MYD88 L265P
    gain-of-function variant (characteristic of Waldenstrom disease) may link the
    autoinflammatory and monoclonal-gammopathy arms. This remains a hypothesis
    rather than an established causal variant in Schnitzler syndrome.
  evidence:
  - reference: PMID:31228950
    reference_title: "Schnitzler's syndrome - a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we present a novel hypothesis of a shared pathophysiologic mechanism between Schitzler's syndrome and monoclonal gammopathy."
    explanation: >-
      Supports the hypothesized shared (MYD88-related) mechanism between
      Schnitzler syndrome and the monoclonal gammopathy / Waldenstrom disease,
      flagged as a hypothesis rather than an established causal variant.
treatments:
- name: Anakinra (IL-1 Receptor Antagonist)
  description: >
    Anakinra is a recombinant IL-1 receptor antagonist that blocks both IL-1 alpha
    and IL-1 beta. It is a very effective treatment for Schnitzler syndrome,
    producing rapid clinical remission, but requires daily subcutaneous injection
    and symptoms recur shortly after stopping.
  action_category: THERAPEUTIC
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: anakinra
      term:
        id: CHEBI:231683
        label: Anakinra
  evidence:
  - reference: PMID:23087179
    reference_title: "Sustained efficacy of the monoclonal anti-interleukin-1 beta antibody canakinumab in a 9-month trial in Schnitzler's syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The interleukin (IL) 1 receptor antagonist anakinra is a very effective treatment, but requires daily injection and blocks both IL-1α and IL-1β."
    explanation: >-
      Anakinra (an IL-1 receptor antagonist) is a very effective treatment for
      Schnitzler syndrome.
- name: Canakinumab (Anti-IL-1beta Monoclonal Antibody)
  description: >
    Canakinumab is a selective human monoclonal anti-IL-1 beta antibody with a
    long half-life allowing monthly dosing. A randomized placebo-controlled study
    demonstrated efficacy, with significant improvement in clinical signs,
    inflammatory markers, and quality of life. It is effective in anakinra-treated
    patients and is a key targeted therapy.
  action_category: THERAPEUTIC
  therapeutic_modality: MONOCLONAL_ANTIBODY
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: canakinumab
      term:
        id: NCIT:C80971
        label: Canakinumab
  evidence:
  - reference: PMID:27658762
    reference_title: "Efficacy and safety of canakinumab in Schnitzler syndrome: A multicenter randomized placebo-controlled study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The proportion of patients with complete clinical response at day 7 was significantly higher (P = .001) in the canakinumab-treated group (n = 5 of 7) than in the placebo group (n = 0 of 13)."
    explanation: >-
      In a randomized placebo-controlled study, canakinumab produced
      significantly higher complete clinical response than placebo.
  - reference: PMID:23087179
    reference_title: "Sustained efficacy of the monoclonal anti-interleukin-1 beta antibody canakinumab in a 9-month trial in Schnitzler's syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Canakinumab induced complete or clinical remission at day 14 in all eight patients."
    explanation: >-
      Canakinumab induced complete or clinical remission in all patients of a
      9-month open-label trial.
diagnosis:
- name: Strasbourg Diagnostic Criteria
  description: >
    Diagnosis is made using the Strasbourg diagnostic criteria, which require the
    two obligate features (chronic urticarial rash and a monoclonal IgM or IgG)
    plus minor criteria (recurrent fever, abnormal bone remodeling, neutrophilic
    dermal infiltrate, leukocytosis/elevated CRP), after excluding infectious,
    lymphoproliferative, and monogenic autoinflammatory mimics.
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of all of them corresponded to the Strasbourg diagnostic criteria."
    explanation: >-
      The Strasbourg diagnostic criteria are the standard for diagnosing
      Schnitzler syndrome in clinical practice.
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Infectious and lymphoproliferative diseases, monogenic AIDs (CAPS, TRAPS, and HIDS) were excluded from all patients at the prehospital stage."
    explanation: >-
      Diagnosis requires exclusion of infectious, lymphoproliferative, and
      monogenic autoinflammatory mimics.
differential_diagnoses:
- name: Cryopyrin-Associated Periodic Syndrome (CAPS)
  description: >
    CAPS and other monogenic autoinflammatory diseases with urticarial rash can
    mimic Schnitzler syndrome but are typically childhood-onset, hereditary, and
    lack a monoclonal gammopathy; they must be excluded.
  distinguishing_features:
  - Germline NLRP3 mutation and earlier (often childhood) onset in CAPS
  - Absence of monoclonal gammopathy in CAPS
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "monogenic AIDs (CAPS, TRAPS, and HIDS) were excluded from all patients at the prehospital stage"
    explanation: >-
      Monogenic autoinflammatory diseases including CAPS are excluded when
      diagnosing Schnitzler syndrome.
- name: Lymphoproliferative Disorder (Waldenstrom Macroglobulinemia)
  description: >
    An overt lymphoproliferative disorder, particularly Waldenstrom
    macroglobulinemia, can present with a monoclonal IgM and must be
    distinguished; Schnitzler syndrome carries an increased long-term risk of
    transformation to such disorders.
  distinguishing_features:
  - Overt clonal lymphoplasmacytic infiltrate/tissue diagnosis in malignancy
  - Schnitzler syndrome adds the chronic urticarial autoinflammatory phenotype
  evidence:
  - reference: PMID:38861148
    reference_title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Infectious and lymphoproliferative diseases, monogenic AIDs (CAPS, TRAPS, and HIDS) were excluded from all patients at the prehospital stage."
    explanation: >-
      Lymphoproliferative disease must be excluded when establishing the
      diagnosis.
discussions:
- discussion_id: gap_schnitzler_gammopathy_link
  prompt: >-
    What is the mechanistic relationship between the autoinflammatory (IL-1-driven)
    features and the monoclonal gammopathy in Schnitzler syndrome?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Monoclonal Gammopathy
  rationale: >-
    Both an urticarial rash and a monoclonal gammopathy are mandatory features,
    but whether the clonal B-cell process drives the autoinflammation, vice
    versa, or both arise from a shared upstream lesion (e.g., somatic MYD88
    L265P, as in Waldenstrom disease) remains unresolved.
  evidence:
  - reference: PMID:38927050
    reference_title: "Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the main question regarding the relationship between autoinflammatory features and monoclonal gammopathy is still unanswered"
    explanation: >-
      Authors explicitly state that the relationship between the autoinflammatory
      features and the monoclonal gammopathy is unresolved.
- discussion_id: gap_schnitzler_no_model
  prompt: >-
    Why is there no validated animal or genetic model of Schnitzler syndrome, and
    how does this limit mechanistic study?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#IL-1 Driven Autoinflammation
  rationale: >-
    Schnitzler syndrome is an acquired, sporadic disorder tied to an aging human
    clonal/innate-immune context with no germline Mendelian cause, and has not
    been recapitulated in a model organism; mechanistic insight derives almost
    entirely from human clinical and ex vivo studies.
  evidence:
  - reference: PMID:38927050
    reference_title: "Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the physiopathology of Schnitzler syndrome remains elusive"
    explanation: >-
      The physiopathology remains elusive, consistent with the absence of a
      validated disease model.
clinical_trials:
- name: NCT01276522
  phase: NOT_APPLICABLE
  status: COMPLETED
  description: >
    Open-label, single-treatment-arm study of monthly subcutaneous canakinumab
    (150 or 300 mg) in patients with active Schnitzler syndrome, assessing the
    efficacy and safety of selective IL-1 beta blockade. Results reported in
    PMID:23087179.
  target_phenotypes:
  - preferred_term: Urticaria
    term:
      id: HP:0001025
      label: Urticaria
  - preferred_term: Recurrent fever
    term:
      id: HP:0001954
      label: Recurrent fever
  evidence:
  - reference: clinicaltrials:NCT01276522
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is a 6-month open-label, single treatment arm study of canakinumab 150 or 300 mg (in case of insufficient response to 150 mg) subcutaneous injection once per month in patients with active Schnitzler syndrome, in which efficacy and safety will be assessed."
    explanation: >-
      Trial evaluated monthly canakinumab (IL-1 beta blockade) for efficacy and
      safety in active Schnitzler syndrome.
references:
- reference: PMID:25905009
  title: "Schnitzler's syndrome: lessons from 281 cases."
- reference: PMID:38927050
  title: "Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management."
- reference: PMID:38861148
  title: "Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort."
- reference: PMID:23087179
  title: "Sustained efficacy of the monoclonal anti-interleukin-1 beta antibody canakinumab in a 9-month trial in Schnitzler's syndrome."
- reference: PMID:27658762
  title: "Efficacy and safety of canakinumab in Schnitzler syndrome: A multicenter randomized placebo-controlled study."
- reference: PMID:31228950
  title: "Schnitzler's syndrome - a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease."
📚

References & Deep Research

References

6
PMID:25905009
Schnitzler's syndrome: lessons from 281 cases.
No top-level findings curated for this source.
PMID:38927050
Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management.
No top-level findings curated for this source.
PMID:38861148
Schnitzler's Syndrome-Diagnostic Experience, Approaches to Therapy, and Patient Management according to a Multicenter Russian Cohort.
No top-level findings curated for this source.
PMID:23087179
Sustained efficacy of the monoclonal anti-interleukin-1 beta antibody canakinumab in a 9-month trial in Schnitzler's syndrome.
No top-level findings curated for this source.
PMID:27658762
Efficacy and safety of canakinumab in Schnitzler syndrome: A multicenter randomized placebo-controlled study.
No top-level findings curated for this source.
PMID:31228950
Schnitzler's syndrome - a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease.
No top-level findings curated for this source.

Deep Research

1
Claude Code ▸
1. Disease Information
claude-haiku-4-5-20251001, claude-opus-4-8[1m] 11 citations 2026-06-29T11:02:36.055331

1. Disease Information

Overview. Schnitzler syndrome is a rare, acquired, late-onset autoinflammatory disorder defined by the combination of a chronic urticarial rash plus a monoclonal gammopathy (IgM in >90% of cases, IgG in a minority), accompanied by signs of systemic inflammation: recurrent fever, bone pain, arthralgia/arthritis, lymphadenopathy, fatigue, and markedly elevated acute-phase reactants. It sits at the crossroads of autoinflammation and clonal B-cell/plasma-cell disease, and is driven by dysregulated interleukin-1β (IL-1β) signaling — the basis for its near-pathognomonic response to IL-1 blockade. First described by the French dermatologist Liliane Schnitzler in 1972.

"Schnitzler syndrome is a rare disorder characterized by a chronic urticarial rash and monoclonal gammopathy (IgM in more than 90% of the cases)… Interleukin-1 is considered the key mediator, and interleukin-1 inhibitors are considered first line treatment." (Case series, Case Reports in Rheumatology 2018)

Key identifiers (verify against MONDO/Orphanet at curation time): - Orphanet: ORPHA:37748 (Schnitzler syndrome) — CC-BY, citable as ORPHA:37748 - MONDO: MONDO:0008756 (Schnitzler syndrome) — suggested primary MONDO ID; confirm with runoak -i sqlite:obo:mondo info MONDO:0008756 -O obo - OMIM: No dedicated OMIM phenotype number — the disorder is acquired/sporadic, not Mendelian, so OMIM does not assign a gene-disease MIM. (This is itself a meaningful curation fact.) - ICD-10: No specific code; coded pragmatically under D47.2 (monoclonal gammopathy of undetermined significance) or L50.8 (other urticaria). ICD-11: best mapped under autoinflammatory/urticarial categories (e.g., EB00 urticaria family / 4A60 autoinflammatory) — no unique stem code. - MeSH: Schnitzler Syndrome (descriptor present in MeSH).

Synonyms / alternative names: Schnitzler's syndrome; chronic urticaria with macroglobulinemia; urticarial vasculitis–macroglobulinemia (historical, imprecise).

Data derivation: Disease-level aggregated resources — Orphanet, expert reviews, and pooled case-series — not EHR/individual-patient registries. The single most useful quantitative source is the pooled 281-case review (PMID:25905009).

2. Etiology

Causal factors. Schnitzler syndrome is acquired and sporadic; there is no inherited cause. The proximate driver is inappropriate activation of the innate immune system with IL-1β overproduction, occurring in the context of a clonal IgM (rarely IgG) gammopathy. The relationship between the monoclonal component and the inflammation is not settled — they may be parallel manifestations of one clonal/innate-immune lesion rather than one causing the other.

Genetic risk factors. - No germline pathogenic variant is required or established. Critically, despite the clinical overlap with cryopyrin-associated periodic syndromes (CAPS), NLRP3 germline mutations are absent: "no somatic or germline variations of NLRP3 were identified by deep NGS in two large cohorts of 21 and 40 patients" (PMID:38927050). - Somatic MYD88 L265P — a recurrent gain-of-function variant — has been detected in a subset of patients (in clonal cells / bone marrow). It is the same variant present in >90% of Waldenström macroglobulinemia, and is the leading molecular link between the inflammatory and lymphoproliferative arms (PMID:31228950; PMID:38927050). Variant: MYD88 (HGNC:7562) c.794T>C, p.Leu265Pro, somatic, gain-of-function. - Low-frequency somatic mosaic NLRP3 variants have been reported in occasional "Schnitzler-like" patients but are not a consistent finding.

Environmental / lifestyle risk factors. None established. Onset is age-related (typically >50 years); no confirmed occupational, infectious, dietary, or toxic trigger. Slight male predominance (see §9).

Protective factors. None identified (no protective alleles, no dietary/lifestyle protection described). This reflects how little is known about initiation rather than a true absence.

Gene–environment interaction. Not characterized. The plausible model is a somatic clonal lesion (MYD88 L265P → constitutive NF-κB priming) interacting with innate-immune inflammasome tone in an aging host, but this is mechanistic hypothesis, not established G×E data.

3. Phenotypes

Frequencies below are from the pooled 281-case review (PMID:25905009) unless noted. Onset is adult/late-onset (median 51 y); course is chronic, relapsing-remitting / episodic but lifelong without treatment.

Phenotype Type Frequency Suggested HPO term
Chronic urticarial rash (non-pruritic, pink-red papules/plaques, individual lesions <24 h, monomorphic, spare face) Clinical sign (skin) 100% (obligate) HP:0001025 Urticaria
Recurrent/intermittent fever (can exceed 40 °C, well-tolerated, non-periodic) Symptom 72% HP:0001954 Recurrent fever (or HP:0001945 Fever)
Arthralgia / arthritis (non-erosive; large joints) Symptom/sign 68% HP:0002829 Arthralgia; HP:0001369 Arthritis
Bone pain (lower limbs — tibia, femur, iliac — predominant; from osteosclerosis/hyperostosis) Symptom 55% HP:0002653 Bone pain
Lymphadenopathy (axillary/inguinal, reactive) Sign 26% HP:0002716 Lymphadenopathy
Pruritus Symptom 21% HP:0000989 Pruritus
Weight loss Symptom 16% HP:0001824 Weight loss
Fatigue / asthenia Symptom Common (most patients) HP:0012378 Fatigue
Hepatomegaly / splenomegaly Sign Minority HP:0002240 Hepatomegaly; HP:0001744 Splenomegaly
Anemia (of chronic inflammation) Lab Common, secondary HP:0001903 Anemia
Neutrophilic leukocytosis Lab Common HP:0011897 Neutrophilia
Elevated CRP / acute-phase response Lab Near-universal HP:0011227 Elevated C-reactive protein level
Monoclonal IgM gammopathy Lab (obligate) >90% HP:0031030 Monoclonal immunoglobulin M proteinemia (or HP:0002720 Decreased/abnormal immunoglobulin... — verify)
Elevated ESR Lab Common HP:0003565 Elevated erythrocyte sedimentation rate
Bone hyperostosis / osteosclerosis (imaging) Imaging/lab Radiograph hyperostosis 39%; scintigraphy uptake 85% HP:0100774 Hyperostosis; HP:0011001 Increased bone mineral density
Angioedema Sign Rare/atypical HP:0100665 Angioedema

Per-phenotype characteristics. - Rash: the hallmark — a neutrophilic urticarial dermatosis, NOT classic allergic wheals: lesions are usually non-pruritic (pruritus in only ~21%), each resolves within 24 h, leaves no scarring/purpura, and spares angioedema. Often the first manifestation, sometimes by years. - Fever: recurrent, intermittent, can be high but is characteristically well-tolerated; not strictly periodic (distinguishing it from hereditary periodic fevers). - Bone involvement: distal femur and proximal tibia osteosclerosis/hyperostosis is a relatively specific feature; bone scintigraphy shows increased uptake in ~85%. - Severity/progression: individually mild-to-moderate per flare but cumulatively debilitating; QoL is severely impaired pre-treatment and dramatically restored by IL-1 blockade.

Quality-of-life impact. Marked before treatment — chronic rash, recurrent fever, bone pain, and fatigue impair daily functioning; canakinumab/anakinra trials documented significant improvement in QoL scores alongside CRP/SAA normalization (PMID:27658762; PMID:23087179).

4. Genetic / Molecular Information

  • Causal genes: None inherited. The disorder is acquired. The recurrent somatic driver is MYD88 (HGNC:7562; OMIM gene 602170; chr3p22.2), variant p.Leu265Pro (L265P) — gain-of-function, found in clonal cells of a subset of patients and the molecular bridge to Waldenström macroglobulinemia (PMID:31228950).
  • NLRP3 (HGNC:16400): No germline or somatic NLRP3 variants by deep NGS in two cohorts (n=21, n=40) — explicitly distinguishing Schnitzler from CAPS (PMID:38927050). This negative finding is itself a key curatable fact.
  • Variant classification / type: MYD88 L265P — missense, somatic, gain-of-function, dominant-acting at the cellular signaling level. Well established as pathogenic/oncogenic in B-cell lymphoma contexts (ClinVar/COSMIC); in Schnitzler it is a clonal somatic marker, not a germline disease allele.
  • Allele frequency: Not a population polymorphism; somatic, absent from gnomAD as a germline variant.
  • Functional consequence: L265P stabilizes a MYD88 multimer that constitutively engages IRAK4/IRAK1 → persistent NF-κB activation, priming transcription of NLRP3 and pro-IL-1β; it is also reported to resist caspase-1-mediated negative feedback of MyD88 signaling (PMID:38927050).
  • Modifier genes / epigenetics / chromosomal abnormalities: Not characterized. No methylation signature, no recurrent karyotypic lesion described.

5. Environmental Information

  • Environmental/occupational/toxin factors: None established.
  • Lifestyle factors: None established.
  • Infectious agents: None — Schnitzler is not infection-triggered. (NCBI Taxonomy / pathogen sections not applicable.) Fever and inflammation are sterile/autoinflammatory.

This section is genuinely sparse for this disease — the etiology is intrinsic (clonal + innate-immune), not exposure-driven.

6. Mechanism / Pathophysiology

Central axis: IL-1β-driven autoinflammation. The dominant, therapy-validated mechanism is overproduction/over-signaling of IL-1β, with the NLRP3 inflammasome as the assembly platform. The most compelling evidence is therapeutic: IL-1 blockade produces near-complete remission within hours (PMID:25905009; PMID:38927050).

Proposed causal chain (upstream → downstream):

  1. Clonal/innate priming (upstream). A somatic lesion — prototypically MYD88 L265P — drives constitutive NF-κB activation in myeloid and/or clonal B-cells, providing a persistent "signal 1" that upregulates NLRP3 and pro-IL-1β transcription (PMID:31228950; PMID:38927050).
  2. GO: GO:0007249 I-κB kinase/NF-κB signaling; GO:0002224 toll-like receptor signaling pathway (MyD88-dependent).
  3. NLRP3 inflammasome activation ("signal 2"). Despite no NLRP3 mutation, the inflammasome is hyperactive: assembly of NLRP3–ASC–pro-caspase-1, caspase-1 autoactivation, cleavage of pro-IL-1β → mature IL-1β; pyroptotic release marked by elevated extracellular ASC specks (PMID:38927050).
  4. GO: GO:0002218 activation of innate immune response; GO:0072559 NLRP3 inflammasome complex (CC); GO:0050700 CARD domain binding; GO:0097202 activation of cysteine-type endopeptidase activity; GO:0070269 pyroptosis.
  5. Cytokine cascade (downstream). Elevated IL-1β, IL-6, IL-18; IL-6 drives the acute-phase response (CRP, serum amyloid A), fever, and anemia of inflammation.
  6. GO: GO:0050715 positive regulation of cytokine secretion; GO:0006954 inflammatory response; GO:0061702 canonical inflammasome complex.
  7. Effector cells. Dermal mast cells identified as a primary IL-1β source in lesional skin (PMID:38927050); neutrophils recruited into the dermis produce the characteristic neutrophilic urticarial dermatosis (interstitial/perivascular neutrophilic infiltrate, leukocytoclasis, no vasculitis, no dermal edema).
  8. CL: CL:0000097 mast cell; CL:0000775 neutrophil; CL:0000235 macrophage; CL:0000786 plasma cell / CL:0000787 memory B cell (clonal compartment).
  9. Clinical manifestations. Rash (neutrophilic urticaria), fever, bone remodeling (osteosclerosis), arthralgia, fatigue.

Bone phenotype mechanism. IL-1/IL-6-driven abnormal bone remodeling produces osteosclerosis/hyperostosis (paradoxically osteoblastic), most marked at distal femur/proximal tibia — a relatively specific imaging clue.

Immune system involvement. Prototypic autoinflammation (innate, antigen-independent) layered on a clonal B-cell/plasma-cell process. Not classic autoimmunity (no pathogenic autoantibody to self), though the monoclonal IgM is sometimes proposed to contribute (e.g., complement engagement) — unproven.

Molecular profiling. Serum cytokine studies show elevated IL-6/IL-18 and modestly elevated IL-1β; lesional skin transcriptomic/IHC work localizes IL-1β to mast cells. No large -omics (proteomic/metabolomic/single-cell) signature is yet established — a genuine knowledge gap.

Protein dysfunction (UniProt anchors): MYD88 (UniProt Q99836); NLRP3/cryopyrin (Q96P20); IL-1β (P01584); caspase-1 (P29466); ASC/PYCARD (Q9ULZ3).

7. Anatomical Structures Affected

  • Skin (primary): UBERON:0002097 skin of body / UBERON:0002067 dermis — site of neutrophilic urticarial dermatosis. Lesions favor trunk and limbs, spare the face; bilateral/generalized.
  • Bone (primary, characteristic): UBERON:0002481 bone tissue; specifically distal femur (UBERON:0009980) and proximal tibia / tibia (UBERON:0000979) osteosclerosis; iliac bone involvement also described.
  • Joints (secondary): UBERON:0000982 skeletal joint — non-erosive arthralgia/arthritis, large joints.
  • Lymphoid / hematopoietic: UBERON:0000029 lymph node (reactive lymphadenopathy); UBERON:0002106 spleen, UBERON:0002107 liver (occasional organomegaly); bone marrow (UBERON:0002371) — clonal plasma/B-cell compartment.
  • Blood: UBERON:0000178 blood — monoclonal protein, leukocytosis, anemia, acute-phase reactants.
  • Body systems: integumentary, musculoskeletal, hematologic/lymphatic, and (systemically) immune.
  • Subcellular (GO CC): GO:0072559 NLRP3 inflammasome complex; GO:0005829 cytosol (inflammasome assembly); GO:0005886 plasma membrane (IL-1R signaling).
  • Lateralization: rash and bone changes are typically bilateral/symmetric/generalized.

8. Temporal Development

  • Onset: Adult/late-onset — median age ~51 years (PMID:25905009); onset before 35 is rare; essentially never congenital/pediatric.
  • Onset pattern: Insidious/chronic, frequently beginning with isolated chronic urticaria; the monoclonal protein and full systemic picture may emerge over months to years.
  • Course: Chronic, relapsing-remitting / episodic flares of rash and fever on a background of persistent inflammation; lifelong without treatment. Spontaneous complete remission is exceptionally rare ("only one case" reported, PMID:38927050).
  • Progression / critical windows:
  • AA amyloidosis can develop after years of uncontrolled inflammation — a window where sustained IL-1 blockade is preventive.
  • Lymphoproliferative transformation (Waldenström macroglobulinemia / lymphoplasmacytic lymphoma) emerges at a median ~8 years after onset (range often cited 10–20 y), mandating long-term hematologic surveillance.
  • Treatment-induced remission: IL-1 blockade induces rapid (hours-to-days), reproducible clinical remission, but is suppressive, not curative — symptoms recur within 24–48 h of stopping anakinra.

9. Inheritance and Population

  • Epidemiology: Rare. Prevalence unknown; ~300 cases published worldwide (≈150 in earlier counts, growing), predominantly European/Caucasian, reported in >25 countries. Orphanet classes it as rare (ORPHA:37748).
  • Inheritance: Not heritable — acquired/sporadic. No AD/AR/X-linked/mitochondrial pattern; no penetrance/expressivity/anticipation/founder-effect/carrier-frequency concepts apply. (These template sub-items are not applicable.)
  • Demographics:
  • Sex ratio ~1.5:1 male:female (slight male predominance) (PMID:25905009).
  • Immunoglobulin profile: monoclonal IgMκ in ~85% (IgMλ ~8%), IgG ~6%; kappa light chain in ~89% overall.
  • Geographic: apparent European concentration likely reflects ascertainment/awareness rather than true biology.

10. Diagnostics

Diagnostic criteria — Strasbourg criteria (2012/2013 expert consensus; validated by Gusdorf et al. 2017, Allergy, DOI:10.1111/all.13035).

Two obligate criteria (both required): 1. Chronic urticarial rash, AND 2. Monoclonal IgM or IgG

Minor criteria: - Recurrent fever (>38 °C, no other cause) - Objective signs of abnormal bone remodeling (with or without bone pain) — e.g., osteosclerosis/hyperostosis on imaging/scintigraphy - Neutrophilic dermal infiltrate on skin biopsy (neutrophilic urticarial dermatosis, no vasculitis/edema) - Leukocytosis (neutrophils >10,000/mm³) and/or elevated CRP (>30 mg/L)

Definite diagnosis: 2 obligate + ≥2 minor (IgM) or ≥3 minor (IgG). Probable diagnosis: 2 obligate + ≥1 minor (IgM) or ≥2 minor (IgG).

Laboratory workup (LOINC-codable analytes): - Serum protein electrophoresis + immunofixation → monoclonal IgM (κ) — the obligate gammopathy. - CRP (LOINC 1988-5), ESR, serum amyloid A — markedly elevated; track disease/treatment. - CBC — neutrophilic leukocytosis, anemia of chronic disease. - MYD88 L265P assay on peripheral blood/bone marrow in selected patients (links to Waldenström risk). - Bone marrow biopsy to exclude/monitor lymphoplasmacytic disorder.

Imaging: plain radiographs (hyperostosis ~39%), bone scintigraphy (increased uptake ~85% — sensitive for the osteosclerotic lesions), MRI/PET for marrow/bone.

Histopathology (skin biopsy): neutrophilic urticarial dermatosis — perivascular and interstitial neutrophils with leukocytoclasis, without true vasculitis and without significant dermal edema.

Differential diagnosis (with distinguishing features): - CAPS / Muckle-Wells / NOMID — germline NLRP3, childhood onset, sensorineural deafness; Schnitzler is adult, no NLRP3 mutation, has gammopathy. - Adult-onset Still disease — ferritin-high, salmon rash, no monoclonal protein. - Chronic spontaneous urticaria — pruritic, no fever/gammopathy/bone disease. - Urticarial vasculitis — true leukocytoclastic vasculitis, lesions >24 h with purpura. - Waldenström macroglobulinemia / IgM-MGUS — the gammopathy overlaps; Schnitzler adds the autoinflammatory phenotype. - Hyper-IgD / TRAPS / other periodic fevers — hereditary, earlier onset.

Screening: No population/newborn screening (acquired, rare). Surveillance is longitudinal — periodic monoclonal-protein quantitation and clinical/hematologic monitoring for lymphoproliferative transformation and amyloidosis.

11. Outcome / Prognosis

  • Survival: Generally good/near-normal life expectancy in the IL-1-blockade era; mortality is driven not by the inflammation itself but by its complications.
  • Major complications:
  • Lymphoproliferative malignancy in ~15–20% (Waldenström macroglobulinemia most common; also lymphoplasmacytic lymphoma, rarely IgM myeloma), typically after 10–20 years; pooled review found 12% (35/281) at median 8-year follow-up — true lifetime risk likely higher (PMID:25905009).
  • AA (secondary) amyloidosis in ~2% (6/281) from chronic SAA elevation — historically a cause of renal failure/death; preventable by controlling inflammation.
  • Anemia of chronic inflammation, fatigue, debilitating QoL pre-treatment.
  • Recovery potential: Inflammation is highly controllable (IL-1 blockade), but the disease is chronic/lifelong and treatment is suppressive, not curative; the monoclonal gammopathy and malignancy risk are not altered by IL-1 inhibitors.
  • Prognostic factors: duration of uncontrolled inflammation (amyloidosis risk), rising/transforming monoclonal component, evolving cytopenias or organomegaly (lymphoma signal). SAA/CRP serve as activity and amyloid-risk biomarkers.

12. Treatment

First-line: IL-1 blockade — the defining, near-pathognomonic therapy (MAXO:0000058 anti-inflammatory agent therapy / MAXO:0000986-type targeted biologic; treatment action = NCIT:C15986 Pharmacotherapy with biologic therapeutic_agent).

  1. Anakinra (recombinant IL-1 receptor antagonist; CHEBI:472604 anakinra / NCIT:C1598 Anakinra).
  2. Most established therapy; complete remission in >90% of cases (81/86 patients high efficacy, PMID:25905009). Symptoms resolve within hours; relapse 24–48 h after stopping (short half-life ~3–9.5 h → daily SC dosing).
  3. Therapeutic modality: protein/antagonist biologic; MAXO/NCIT pharmacotherapy.
  4. Canakinumab (anti-IL-1β monoclonal antibody; NCIT:C75984 Canakinumab; modality MONOCLONAL_ANTIBODY).
  5. Randomized, placebo-controlled trial evidence: complete clinical response at day 7 in 5/7 canakinumab vs 0/13 placebo (P=.001), with significant CRP/SAA and QoL improvement (PMID:27658762; PMC4597402). 9-month open trial: remission in all 8 patients by day 14, sustained (PMID:23087179). Long half-life (~3–4 weeks) → monthly (or longer) dosing. First choice for anakinra-refractory patients.
  6. Rilonacept (IL-1 decoy receptor, binds IL-1α/β; NCIT:C66952 Rilonacept) — open-label efficacy (8-patient cohort); weekly SC.

Second-line / alternatives: - Tocilizumab (anti-IL-6R) — initial response then waning efficacy in a 9-patient series. - Ibrutinib (BTK inhibitor) — case-level efficacy with a rational dual benefit (inflammasome + MYD88-driven clonal disease). - Colchicine (~1 mg/day) — mild disease/adjunct. - Anti-IgM / B-cell–directed (rituximab) when an overt lymphoplasmacytic disorder coexists. - NSAIDs, corticosteroids, conventional immunosuppressants — historically used, generally only partially effective and steroid-sparing is a goal.

Pharmacogenomics: MYD88 L265P status is the actionable molecular marker — flags Waldenström risk and provides biologic rationale for BTK inhibition; no validated PK/PGx-by-genotype dosing.

Treatment strategy / outcomes: Algorithm = confirm Strasbourg criteria → start anakinra (also a diagnostic test, given the dramatic response) → switch to canakinumab/rilonacept for convenience or anakinra failure → escalate to B-cell-directed/BTK therapy if clonal disease progresses. IL-1 blockade reverses inflammation, normalizes acute-phase reactants, restores QoL, and is expected to prevent AA amyloidosis — but does not prevent lymphoproliferative transformation. Adverse events (canakinumab trials): respiratory and GI infections, neutropenia, injection-site reactions.

Suggested MAXO terms: MAXO:0000058 (anti-inflammatory agent therapy); MAXO:0001013-type biologic/immunomodulatory therapy; broad action NCIT:C15986 Pharmacotherapy with therapeutic_agent biologics (anakinra/canakinumab/rilonacept) — per dismech therapeutic-agent pattern, prefer NCIT agent terms for biologics lacking clean CHEBI entries.

13. Prevention

  • Primary prevention: None — etiology unknown, acquired, no modifiable risk factor or vaccine.
  • Secondary prevention: Early recognition (apply Strasbourg criteria to "chronic urticaria + monoclonal IgM") shortens diagnostic delay (historically years).
  • Tertiary prevention (the real lever):
  • Sustained IL-1 blockade to prevent AA amyloidosis (by normalizing SAA).
  • Long-term hematologic surveillance (serial monoclonal-protein quantitation, exam, blood counts) for early detection of Waldenström/lymphoplasmacytic transformation.
  • Counseling: Not genetic counseling (not heritable) — rather patient education on chronicity, the need for ongoing therapy, and malignancy monitoring.
  • Public health / immunization / environmental measures: Not applicable.

14. Other Species / Natural Disease

Not applicable / none reported. Schnitzler syndrome is a human-only acquired syndrome; there is no naturally occurring animal counterpart (no OMIA entry), no breed predisposition, and no zoonotic/cross-species dimension. The relevant gene MYD88 is highly conserved (orthologs across vertebrates), but no animal exhibits the Schnitzler clinical syndrome. NCBI Taxon for the affected species: NCBITaxon:9606 (Homo sapiens) only.

15. Model Organisms

No dedicated animal model exists. Because the disorder is acquired, somatic, and tied to an aging human clonal/innate-immune context, it has not been recapitulated in mice, zebrafish, or other model organisms. Mechanistic insight comes from: - In vitro / ex vivo human studies (patient PBMCs, monocytes, lesional skin) demonstrating NLRP3-inflammasome hyperactivity, IL-1β/IL-18 elevation, ASC-speck release, and mast-cell IL-1β localization (PMID:38927050) — evidence_source IN_VITRO / HUMAN_CLINICAL. - Cellular MYD88 L265P models (from Waldenström/lymphoma biology) informing the NF-κB-priming mechanism — relevant but not Schnitzler-specific.

This is a genuine knowledge gap: a faithful model would need to reproduce the somatic-clonal + autoinflammatory overlap, which no current system does. (Appropriate dismech treatment: a KNOWLEDGE_GAP discussion noting absence of an animal model, not a fabricated MODEL_ORGANISM evidence item.)

Curation Notes & Suggested Evidence Anchors

High-value PMIDs (fetch + snippet-validate before use): - PMID:25905009 — de Koning HD. Schnitzler's syndrome: lessons from 281 cases. (Pooled frequencies, demographics, malignancy 12%, amyloidosis 2%, anakinra >90% response.) — primary epidemiology source. - PMID:38927050 — Braud A, Lipsker D. Schnitzler Syndrome: Insights into Its Pathogenesis, Clinical Manifestations, and Current Management. Biomolecules 2024;14(6):646. — best recent mechanism + management review. - PMID:27658762 — Krause K, et al. Efficacy and safety of canakinumab in Schnitzler syndrome: a multicenter randomized placebo-controlled study. — RCT (HUMAN_CLINICAL, the strongest treatment evidence). - PMID:23087179 — Vanderschueren S, Knockaert D. Sustained efficacy of canakinumab... 9-month trial. — open-label trial. - PMID:31228950 — Schnitzler's syndrome — a novel hypothesis of a shared pathophysiologic mechanism with Waldenström's disease (MYD88 L265P link). - DOI:10.1111/all.13035 (Gusdorf 2017, Allergy) — Strasbourg criteria validation. - ORPHA:37748 — Orphanet record (structured-source citable for definition/prevalence/synonyms).

Suggested module conformance for the dismech entry: - The disease is a strong candidate to reference an IL-1/inflammasome autoinflammation pattern. There is no existing dedicated NLRP3/IL-1 module in the listed module set, but the mechanism centers on NLRP3 inflammasome → IL-1β; consider whether a new il1_inflammasome_autoinflammation module is warranted (flag as design decision) rather than forcing conformance to an unrelated module. - AA amyloidosis as a downstream complication and lymphoproliferative transformation (Waldenström) are good candidates for comorbidity/trajectory entries rather than core pathophysiology nodes.

Evidence-source tagging reminders: Treatment RCTs and case series → HUMAN_CLINICAL; inflammasome/cytokine cell work → IN_VITRO; the MYD88 L265P NF-κB mechanism drawn from lymphoma cell models → IN_VITRO (and note it is extrapolated, not Schnitzler-derived). No MODEL_ORGANISM evidence is available — do not invent it.

Sources

Verify before committing: MONDO:0008756 label/ID via OAK; exact HPO term IDs/labels (esp. the monoclonal IgM phenotype term); and every snippet as an exact substring of its cached abstract per the dismech anti-hallucination SOP — especially the MYD88/NLRP3 mechanistic claims, which are the highest-risk for paraphrase drift.