Sweet Syndrome

Complex MONDO:0011959 Pathograph 4 Show in embeddings browser Neutrophilic dermatosis

Sweet syndrome (acute febrile neutrophilic dermatosis) is an uncommon, usually non-Mendelian, systemic inflammatory reactive disorder on the autoinflammatory spectrum, considered the prototype of the neutrophilic dermatoses. It is defined by the abrupt onset of tender erythematous papules, plaques, or nodules together with fever, peripheral blood neutrophilia and elevated inflammatory markers (ESR/CRP), and a dense dermal infiltrate of mature neutrophils without leukocytoclastic vasculitis on skin biopsy, with a characteristically prompt response to systemic corticosteroids. It presents in three clinical settings: classical (idiopathic; often post-infectious or associated with pregnancy or inflammatory bowel disease), malignancy-associated (paraneoplastic; most commonly acute myeloid leukemia), and drug-induced (classically granulocyte colony-stimulating factor). The pathogenesis is cytokine-driven neutrophil recruitment and activation (G-CSF, IL-1, IL-6, IL-8, and an IL-17/Th1 adaptive layer); extracutaneous sterile neutrophilic involvement (ocular, musculoskeletal, pulmonary, hepatic, renal, and neurologic "neuro-Sweet") can occur. Because Sweet syndrome can be the cutaneous harbinger of an occult or relapsing hematologic malignancy, new or recurrent disease warrants a malignancy work-up.

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4
Pathophys.
1
Histopath.
11
Phenotypes
2
Hypotheses
2
Gaps
4
Pathograph
5
Medical Actions
3
Subtypes
5
Differentials
5
References
1
Deep Research
🏷

Classifications

Harrison's Chapter
DERMATOLOGY IMMUNE_RHEUMATOLOGIC
◆

Subtypes

3
Classical (idiopathic) Sweet syndrome
Classical or idiopathic Sweet syndrome, most common in women aged 30 to 50 years, frequently preceded by an upper-respiratory or gastrointestinal infection and sometimes associated with inflammatory bowel disease or pregnancy. About one-third of cases recur.
Malignancy-associated (paraneoplastic) Sweet syndrome
Paraneoplastic Sweet syndrome occurring in association with an underlying malignancy, most commonly acute myeloid leukemia and other hematologic dyscrasias; it may precede, follow, or appear concurrent with the cancer diagnosis and can be the cutaneous harbinger of an occult or recurrent malignancy.
Drug-induced Sweet syndrome
Sweet syndrome temporally related to a culprit drug, classically granulocyte colony-stimulating factor (filgrastim); also all-trans retinoic acid, azathioprine, trimethoprim-sulfamethoxazole, and others, with resolution expected after withdrawal of the offending agent.
◈

Mechanistic Hypotheses

2
Cytokine-driven reactive neutrophil activation (autoinflammatory-spectrum)
reactive_cytokine_neutrophil_model CANONICAL
Sweet syndrome is modeled as a reactive hypersensitivity process in which a trigger (antecedent infection, culprit drug, or tumor-associated signals) drives dysregulated cytokine signalling — with a G-CSF and IL-1 core plus an IL-6/IL-8 chemokine and IL-17/Th1 adaptive layer — that recruits and activates mature neutrophils into the dermis, producing the sterile dense neutrophilic infiltrate and clinical plaques. This is the best-supported unifying framework across all three subtypes, though the precise pathogenic mechanism remains to be definitively established.
Show evidence (2 references)
PMID:17655751 SUPPORT Human Clinical
"The pathogenesis of Sweet's syndrome may be multifactorial and still remains to be definitively established. Clinical and laboratory evidence suggests that cytokines have an etiologic role."
Establishes the cytokine-driven, multifactorial pathogenesis as the canonical (if not fully proven) mechanistic framework.
PMID:39704328 SUPPORT Human Clinical
"revealing the predominant role of neutrophil activation and abnormal proliferation as unifying mechanisms in different SS subtypes"
A systematic review of 202 patients identifies neutrophil activation as the unifying molecular mechanism across Sweet syndrome subtypes.
Heterogeneous upstream trigger (infection vs malignancy vs drug)
trigger_heterogeneity CANONICAL
Rather than a single cause, Sweet syndrome has three recognized upstream trigger settings that converge on the same neutrophilic effector pathway: classical/idiopathic disease (often post-infectious or with IBD/pregnancy), malignancy-associated paraneoplastic disease (most commonly acute myeloid leukemia), and drug-induced disease (classically G-CSF). The trigger is heterogeneous; the downstream neutrophilic dermatosis is shared.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"Sweet's syndrome presents in three clinical settings: classical (or idiopathic), malignancy-associated, and drug-induced."
Directly documents the three trigger settings that define Sweet syndrome subtype heterogeneity converging on a shared effector pathway.
?

Discussions and Knowledge Gaps

2
How should the paraneoplastic association between Sweet syndrome and hematologic malignancy (especially acute myeloid leukemia) be modeled and surveilled?
INTERPRETATION OPEN sweet_malignancy_association
Malignancy-associated Sweet syndrome is a paraneoplastic phenomenon, most commonly related to acute myeloid leukemia, and the dermatosis can precede, follow, or appear concurrent with the cancer diagnosis. It can therefore be the cutaneous harbinger of an occult or recurrent hematologic malignancy. This is modeled as a discussion (rather than a fixed structured comorbidity) because the relationship is a longitudinal paraneoplastic association that mandates malignancy work-up and surveillance, not a simple co-occurrence. Features associated with underlying malignancy include cytopenias, absence of arthralgia, and histiocytoid or subcutaneous histopathology.
Show evidence (2 references)
PMID:17655751 SUPPORT Human Clinical
"MASS can be the cutaneous harbinger of either an undiagnosed visceral malignancy in a previously cancer-free individual or an unsuspected cancer recurrence in an oncology patient."
Documents malignancy-associated Sweet syndrome as a cutaneous harbinger of occult or recurrent malignancy, motivating surveillance.
PMID:29107342 SUPPORT Human Clinical
"Acute myeloid leukemia was the most common malignancy (in 24 of 83 patients [29%])"
Quantifies acute myeloid leukemia as the most common associated malignancy in a Sweet syndrome cohort.
What are the epigenetic, metabolomic, and lipidomic signatures of Sweet syndrome, and is there a faithful whole-disease animal model?
KNOWLEDGE GAP OPEN sweet_epigenetics_metabolomics_gap
Attached to
Cytokine Dysregulation and G-CSF/IL-1 Core
The epigenetics, metabolomics, and lipidomics of Sweet syndrome are essentially undefined, and there is no single animal model that faithfully reproduces the integrated clinical syndrome (acute tender plaques plus fever plus corticosteroid responsiveness). Mechanistic understanding rests on human cohort, tissue, and in vitro cytokine studies; the pathogenesis is explicitly noted to remain incompletely established.
⚙

Pathophysiology

4
Cytokine Dysregulation and G-CSF/IL-1 Core
An upstream trigger (antecedent infection, culprit drug such as G-CSF, or tumor-associated signals in the paraneoplastic setting) produces dysregulated cytokine signalling. A granulocyte colony-stimulating factor (G-CSF) and interleukin-1 core, with contributions from IL-6, IL-8/CXCL8, and an IL-17/Th1 adaptive layer, drives neutrophil production, survival, and activation. Cytokine involvement is the best-supported etiologic mechanism, with IL-1 pathway hyperactivation seen in a subset of patients.
Neutrophil CL:0000775
Cytokine production GO:0001816 ↑ INCREASED Inflammatory response GO:0006954 ↑ INCREASED
Downstream
Neutrophil Recruitment and Activation Cytokine and chemokine dysregulation recruits and activates mature neutrophils, driving them into the dermis.
Show evidence (2 references)
PMID:17655751 SUPPORT Human Clinical
"Clinical and laboratory evidence suggests that cytokines have an etiologic role."
Supports cytokine dysregulation as the etiologic driver upstream of neutrophil recruitment.
PMID:39704328 PARTIAL Human Clinical
"we found that hyperactivation of the IL-1 pathway might occur only in a subset of SS patients and adaptive immunity could also play a role in the pathogenic scenario of SS, with a potential significant role of IL-17 axis"
Supports the IL-1 core and an IL-17/adaptive-immunity contribution, while indicating IL-1 hyperactivation is present in only a subset of patients.
Neutrophil Recruitment and Activation
Driven by the dysregulated cytokine/chemokine milieu, mature neutrophils undergo chemotaxis and migration into the reticular dermis and become activated. Neutrophil activation and abnormal proliferation are the unifying molecular mechanism across all Sweet syndrome subtypes.
Mature neutrophil CL:0000096
Neutrophil chemotaxis GO:0030593 ↑ INCREASED Neutrophil migration GO:1990266 ↑ INCREASED Neutrophil activation GO:0042119 ↑ INCREASED
Downstream
Dense Dermal Neutrophilic Infiltrate Recruited, activated neutrophils accumulate as a dense sterile infiltrate in the dermis.
Show evidence (1 reference)
PMID:39704328 SUPPORT Human Clinical
"revealing the predominant role of neutrophil activation and abnormal proliferation as unifying mechanisms in different SS subtypes"
Identifies neutrophil activation and proliferation as the shared effector mechanism recruiting neutrophils across subtypes.
Dense Dermal Neutrophilic Infiltrate
Recruited neutrophils accumulate as a diffuse infiltrate consisting predominantly of mature neutrophils in the upper (papillary and reticular) dermis, with marked papillary dermal edema and interstitial leukocytoclasis (karyorrhectic nuclear debris) but characteristically without true leukocytoclastic vasculitis. This sterile dermal infiltrate is the histopathologic hallmark and diagnostic core of the disease.
Mature neutrophil CL:0000096
Downstream
Tender Erythematous Plaques and Systemic Inflammation The dense dermal neutrophilic infiltrate and accompanying edema manifest clinically as tender erythematous plaques with fever and systemic inflammation.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"a diffuse infiltrate consisting predominantly of mature neutrophils that are typically located in the upper dermis"
Documents the dense mature-neutrophil dermal infiltrate as the pathologic hallmark of Sweet syndrome.
Tender Erythematous Plaques and Systemic Inflammation
The converging neutrophilic dermal process manifests as the clinical syndrome: abrupt onset of tender erythematous papules, plaques, and nodules accompanied by fever, peripheral neutrophilia, and elevated inflammatory markers. Individual lesions are self-limited and typically resolve promptly with systemic corticosteroids, though the syndrome frequently recurs.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"include fever, neutrophilia, tender erythematous skin lesions (papules, nodules, and plaques)"
Documents the clinical output of the pathophysiologic cascade: fever, neutrophilia, and tender erythematous papules/nodules/plaques.
✶

Histopathology

1
Dense Dermal Neutrophilic Infiltrate Without Vasculitis
The diagnostic histopathologic hallmark is a diffuse dermal infiltrate consisting predominantly of mature neutrophils located in the upper dermis, with marked papillary dermal edema and interstitial leukocytoclasis (karyorrhexis), and characteristically WITHOUT leukocytoclastic vasculitis. This dense neutrophilic infiltrate without vasculitis constitutes one of the two required major diagnostic criteria and distinguishes Sweet syndrome from cutaneous leukocytoclastic vasculitis.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"a diffuse infiltrate consisting predominantly of mature neutrophils that are typically located in the upper dermis"
Documents the diagnostic dense dermal mature-neutrophil infiltrate in the upper dermis.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Sweet 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

11
Blood 1
Leukocytosis Increased total leukocyte count HP:0001974
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"include fever, neutrophilia, tender erythematous skin lesions"
The neutrophilia documented in the diagnostic constellation reflects the leukocytosis with neutrophil predominance seen at presentation.
Cardiovascular 1
Ocular involvement Conjunctivitis HP:0000509
Show evidence (1 reference)
PMID:8089280 SUPPORT Human Clinical
"Involvement of the eyes, joints, and oral mucosa"
Documents ocular involvement as an extracutaneous manifestation.
Head and Neck 1
Oral mucosal involvement Oral ulcer HP:0000155
Show evidence (1 reference)
PMID:8089280 SUPPORT Human Clinical
"Involvement of the eyes, joints, and oral mucosa"
Documents oral mucosal involvement as an extracutaneous manifestation.
Immune 1
Cutaneous pustules Pustule HP:0200039
Show evidence (1 reference)
PMID:8089280 SUPPORT Human Clinical
"Raised erythematous plaques with pseudoblistering and occasionally pustules occur on the face, neck, chest, and extremities"
Documents pustules as an occasional cutaneous feature.
Integument 1
Tender erythematous plaques Erythematous plaque HP:0025474
Temporal: ACUTE
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"tender erythematous skin lesions (papules, nodules, and plaques)"
Documents tender erythematous plaques as the defining cutaneous sign.
Metabolism 1
Fever Fever HP:0001945
Show evidence (1 reference)
PMID:8089280 SUPPORT Human Clinical
"accompanied by fever and general malaise"
Documents fever accompanying the cutaneous eruption.
Constitutional 2
Malaise Malaise HP:0033834
Show evidence (1 reference)
PMID:8089280 SUPPORT Human Clinical
"accompanied by fever and general malaise"
Documents general malaise as a constitutional symptom.
Arthralgia Arthralgia HP:0002829
Show evidence (2 references)
PMID:8089280 SUPPORT Human Clinical
"Involvement of the eyes, joints, and oral mucosa"
Documents joint involvement as an extracutaneous manifestation.
PMID:29107342 SUPPORT Human Clinical
"absence of arthralgia (P < .001)"
Documents that absence of arthralgia is significantly associated with malignancy, implying arthralgia is a feature of non-malignant disease.
Other 3
Neutrophilia Neutrophilia in absence of infection HP:0410258
Show evidence (1 reference)
PMID:39704328 SUPPORT Human Clinical
"the sudden onset of well-defined tender papules, plaques and nodules often accompanied by fever, neutrophilia and elevated markers of inflammation"
Documents neutrophilia as a characteristic laboratory feature.
Elevated inflammatory markers Elevated circulating C-reactive protein concentration HP:0011227
Show evidence (1 reference)
PMID:39704328 SUPPORT Human Clinical
"often accompanied by fever, neutrophilia and elevated markers of inflammation"
Documents elevated inflammatory markers as a characteristic finding.
Elevated erythrocyte sedimentation rate Elevated erythrocyte sedimentation rate HP:0003565
Show evidence (1 reference)
PMID:39704328 PARTIAL Human Clinical
"often accompanied by fever, neutrophilia and elevated markers of inflammation"
Elevated markers of inflammation encompass the elevated erythrocyte sedimentation rate used as a diagnostic minor criterion.
💊

Medical Actions

5
Systemic corticosteroids
Action: Pharmacotherapy NCIT:C15986
Agent: prednisone (representative systemic corticosteroid) CHEBI:8382 prednisolone (representative systemic corticosteroid) CHEBI:8378
Systemic corticosteroids (e.g., prednisone or prednisolone, roughly 0.5-1 mg/kg/day tapered over weeks) are the therapeutic gold standard, producing a prompt and often dramatic improvement of both the systemic symptoms and the skin lesions. Topical or intralesional corticosteroids may be used for localized disease.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"Systemic corticosteroids are the therapeutic gold standard for Sweet's syndrome. After initiation of treatment with systemic corticosteroids, there is a prompt response"
Establishes systemic corticosteroids as the gold-standard first-line treatment with a prompt response.
Potassium iodide
Action: Pharmacotherapy NCIT:C15986
Agent: potassium iodide CHEBI:8346
Potassium iodide is a recognized alternative first-line oral systemic agent, useful when corticosteroids are contraindicated.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"Other first-line oral systemic agents are potassium iodide and colchicine."
Documents potassium iodide as an alternative first-line oral agent.
Colchicine
Action: Pharmacotherapy NCIT:C15986
Agent: colchicine CHEBI:23359
Colchicine is a recognized alternative first-line oral systemic anti-inflammatory option and a steroid-sparing choice.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"Other first-line oral systemic agents are potassium iodide and colchicine."
Documents colchicine as an alternative first-line oral agent.
Dapsone
Action: Pharmacotherapy NCIT:C15986
Agent: dapsone CHEBI:4325
Dapsone is used as a second-line and steroid-sparing systemic agent. Screen for glucose-6-phosphate dehydrogenase (G6PD) deficiency before use because of hemolysis risk.
Show evidence (1 reference)
PMID:17655751 SUPPORT Human Clinical
"Second-line oral systemic agents include indomethacin, clofazimine, cyclosporine, and dapsone."
Documents dapsone as a second-line systemic agent.
Treatment of the underlying trigger
Action: supportive care MAXO:0000950
Cause-directed therapy is essential: withdrawing a culprit drug (definitive in drug-induced disease), treating the underlying malignancy in paraneoplastic disease (Sweet syndrome often remits with tumor control and flares with relapse), and managing an underlying infection, inflammatory bowel disease, or autoimmune condition.
Show evidence (1 reference)
PMID:17655751 PARTIAL Human Clinical
"Drug-induced Sweet's syndrome (DISS) most commonly occurs in patients who have been treated with granulocyte-colony stimulating factor"
Documents the culprit-drug (G-CSF) trigger whose withdrawal is the definitive treatment of drug-induced disease.
🔬

Biochemical Markers

2
Neutrophilia and leukocytosis
Show evidence (1 reference)
PMID:39704328 SUPPORT Human Clinical
"often accompanied by fever, neutrophilia and elevated markers of inflammation"
Documents neutrophilia as a characteristic laboratory abnormality.
Elevated inflammatory markers (ESR/CRP)
Show evidence (1 reference)
PMID:39704328 SUPPORT Human Clinical
"often accompanied by fever, neutrophilia and elevated markers of inflammation"
Documents elevated inflammatory markers as a laboratory abnormality.
🔀

Differential Diagnoses

5

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

Pyoderma gangrenosum Not Yet Curated MONDO:0018824
Overlapping Features Pyoderma gangrenosum is the other prototypic neutrophilic dermatosis and shares pathergy and neutrophilic histology, but produces ulcerating lesions with undermined violaceous borders rather than the abrupt tender edematous plaques of Sweet syndrome, and both may be paraneoplastic.
Distinguishing Features
  • Sweet syndrome: tender edematous erythematous plaques/nodules, dense dermal neutrophilic infiltrate, lesions heal without scarring
  • Pyoderma gangrenosum: painful ulcers with undermined violaceous borders, often scarring, strong pathergy
Cutaneous leukocytoclastic vasculitis Not Yet Curated MONDO:0019509
Overlapping Features Cutaneous leukocytoclastic (small-vessel) vasculitis can share neutrophilic inflammation and leukocytoclasis, but is defined by true vasculitis with fibrinoid necrosis of vessel walls, whereas the defining major criterion of Sweet syndrome is a neutrophilic infiltrate WITHOUT leukocytoclastic vasculitis.
Distinguishing Features
  • Sweet syndrome: dense dermal neutrophils WITHOUT vasculitis, tender plaques/nodules
  • Leukocytoclastic vasculitis: fibrinoid necrosis of small-vessel walls, palpable purpura
Cellulitis / cutaneous infection Not Yet Curated MONDO:0005230
Overlapping Features Cellulitis is a frequent clinical mimic because Sweet syndrome plaques are tender, erythematous, and febrile, but the Sweet syndrome infiltrate is sterile and does not respond to antibiotics, whereas it responds dramatically to corticosteroids.
Distinguishing Features
  • Sweet syndrome: sterile neutrophilic infiltrate, no response to antibiotics, dramatic corticosteroid response
  • Cellulitis: bacterial infection, responds to antibiotics, positive cultures/portal of entry
Erythema nodosum Not Yet Curated MONDO:0850231
Overlapping Features Erythema nodosum is a septal panniculitis producing tender subcutaneous nodules on the shins, and like Sweet syndrome is reactive/post-infectious, but it lacks the dense dermal mature-neutrophil infiltrate and shows granulomatous septal panniculitis instead.
Distinguishing Features
  • Sweet syndrome: dermal mature-neutrophil infiltrate, plaques/nodules on face, neck, upper limbs
  • Erythema nodosum: septal panniculitis with granulomas, tender nodules on anterior shins
Behcet disease MONDO:0007191
Overlapping Features Behcet disease is a systemic variable-vessel vasculitis on the neutrophilic/ autoinflammatory spectrum with pathergy and can produce Sweet-like lesions, but is defined by recurrent oral and genital ulceration and ocular disease with a chronic relapsing multisystem course rather than the abrupt, corticosteroid-responsive dermal plaques of Sweet syndrome.
Distinguishing Features
  • Sweet syndrome: abrupt tender dermal plaques, dense dermal neutrophils, corticosteroid-responsive
  • Behcet disease: recurrent oral and genital ulcers, uveitis, pathergy, chronic relapsing multisystem vasculitis
{ }

Source YAML

click to show 
name: Sweet Syndrome
creation_date: "2026-06-30T00:00:00Z"
category: Complex
disease_term:
  preferred_term: Sweet syndrome
  term:
    id: MONDO:0011959
    label: sweet syndrome
parents:
- Neutrophilic dermatosis
description: >-
  Sweet syndrome (acute febrile neutrophilic dermatosis) is an uncommon,
  usually non-Mendelian, systemic inflammatory reactive disorder on the
  autoinflammatory spectrum, considered the prototype of the neutrophilic
  dermatoses. It is defined by the abrupt onset of tender erythematous papules,
  plaques, or nodules together with fever, peripheral blood neutrophilia and
  elevated inflammatory markers (ESR/CRP), and a dense dermal infiltrate of
  mature neutrophils without leukocytoclastic vasculitis on skin biopsy, with a
  characteristically prompt response to systemic corticosteroids. It presents
  in three clinical settings: classical (idiopathic; often post-infectious or
  associated with pregnancy or inflammatory bowel disease),
  malignancy-associated (paraneoplastic; most commonly acute myeloid
  leukemia), and drug-induced (classically granulocyte colony-stimulating
  factor). The
  pathogenesis is cytokine-driven neutrophil recruitment and activation
  (G-CSF, IL-1, IL-6, IL-8, and an IL-17/Th1 adaptive layer); extracutaneous
  sterile neutrophilic involvement (ocular, musculoskeletal, pulmonary,
  hepatic, renal, and neurologic "neuro-Sweet") can occur. Because Sweet
  syndrome can be the cutaneous harbinger of an occult or relapsing
  hematologic malignancy, new or recurrent disease warrants a malignancy
  work-up.

references:
- reference: PMID:14201182
  title: "AN ACUTE FEBRILE NEUTROPHILIC DERMATOSIS."
- reference: PMID:17655751
  title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
- reference: PMID:8089280
  title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
- reference: PMID:29107342
  title: "Sweet syndrome in patients with and without malignancy: A retrospective analysis of 83 patients from a tertiary academic referral center."
- reference: PMID:39704328
  title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."

has_subtypes:
- name: Classical
  display_name: Classical (idiopathic) Sweet syndrome
  description: >-
    Classical or idiopathic Sweet syndrome, most common in women aged 30 to 50
    years, frequently preceded by an upper-respiratory or gastrointestinal
    infection and sometimes associated with inflammatory bowel disease or
    pregnancy. About one-third of cases recur.
- name: Malignancy-associated
  display_name: Malignancy-associated (paraneoplastic) Sweet syndrome
  description: >-
    Paraneoplastic Sweet syndrome occurring in association with an underlying
    malignancy, most commonly acute myeloid leukemia and other hematologic
    dyscrasias; it may precede, follow, or appear concurrent with the cancer
    diagnosis and can be the cutaneous harbinger of an occult or recurrent
    malignancy.
- name: Drug-induced
  display_name: Drug-induced Sweet syndrome
  description: >-
    Sweet syndrome temporally related to a culprit drug, classically
    granulocyte colony-stimulating factor (filgrastim); also all-trans
    retinoic acid, azathioprine, trimethoprim-sulfamethoxazole, and others,
    with resolution expected after withdrawal of the offending agent.

mechanistic_hypotheses:
- hypothesis_group_id: reactive_cytokine_neutrophil_model
  hypothesis_label: Cytokine-driven reactive neutrophil activation (autoinflammatory-spectrum)
  status: CANONICAL
  description: >-
    Sweet syndrome is modeled as a reactive hypersensitivity process in which a
    trigger (antecedent infection, culprit drug, or tumor-associated signals)
    drives dysregulated cytokine signalling — with a G-CSF and IL-1 core plus
    an IL-6/IL-8 chemokine and IL-17/Th1 adaptive layer — that recruits and
    activates mature neutrophils into the dermis, producing the sterile dense
    neutrophilic infiltrate and clinical plaques. This is the best-supported
    unifying framework across all three subtypes, though the precise pathogenic
    mechanism remains to be definitively established.
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The pathogenesis of Sweet's syndrome may be multifactorial and still
      remains to be definitively established. Clinical and laboratory evidence
      suggests that cytokines have an etiologic role.
    explanation: >-
      Establishes the cytokine-driven, multifactorial pathogenesis as the
      canonical (if not fully proven) mechanistic framework.
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      revealing the predominant role of neutrophil activation and abnormal
      proliferation as unifying mechanisms in different SS subtypes
    explanation: >-
      A systematic review of 202 patients identifies neutrophil activation as
      the unifying molecular mechanism across Sweet syndrome subtypes.
- hypothesis_group_id: trigger_heterogeneity
  hypothesis_label: Heterogeneous upstream trigger (infection vs malignancy vs drug)
  status: CANONICAL
  description: >-
    Rather than a single cause, Sweet syndrome has three recognized upstream
    trigger settings that converge on the same neutrophilic effector pathway:
    classical/idiopathic disease (often post-infectious or with IBD/pregnancy),
    malignancy-associated paraneoplastic disease (most commonly acute myeloid
    leukemia), and drug-induced disease (classically G-CSF). The trigger is
    heterogeneous; the downstream neutrophilic dermatosis is shared.
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Sweet's syndrome presents in three clinical settings: classical (or
      idiopathic), malignancy-associated, and drug-induced.
    explanation: >-
      Directly documents the three trigger settings that define Sweet syndrome
      subtype heterogeneity converging on a shared effector pathway.

pathophysiology:
- name: Cytokine Dysregulation and G-CSF/IL-1 Core
  description: >-
    An upstream trigger (antecedent infection, culprit drug such as G-CSF, or
    tumor-associated signals in the paraneoplastic setting) produces
    dysregulated cytokine signalling. A granulocyte colony-stimulating factor
    (G-CSF) and interleukin-1 core, with contributions from IL-6, IL-8/CXCL8,
    and an IL-17/Th1 adaptive layer, drives neutrophil production, survival,
    and activation. Cytokine involvement is the best-supported etiologic
    mechanism, with IL-1 pathway hyperactivation seen in a subset of patients.
  cell_types:
  - preferred_term: Neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: Cytokine production
    term:
      id: GO:0001816
      label: cytokine production
    modifier: INCREASED
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  downstream:
  - target: Neutrophil Recruitment and Activation
    description: >-
      Cytokine and chemokine dysregulation recruits and activates mature
      neutrophils, driving them into the dermis.
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical and laboratory evidence suggests that cytokines have an
      etiologic role.
    explanation: >-
      Supports cytokine dysregulation as the etiologic driver upstream of
      neutrophil recruitment.
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we found that hyperactivation of the IL-1 pathway might occur only in a
      subset of SS patients and adaptive immunity could also play a role in the
      pathogenic scenario of SS, with a potential significant role of IL-17 axis
    explanation: >-
      Supports the IL-1 core and an IL-17/adaptive-immunity contribution, while
      indicating IL-1 hyperactivation is present in only a subset of patients.
- name: Neutrophil Recruitment and Activation
  description: >-
    Driven by the dysregulated cytokine/chemokine milieu, mature neutrophils
    undergo chemotaxis and migration into the reticular dermis and become
    activated. Neutrophil activation and abnormal proliferation are the
    unifying molecular mechanism across all Sweet syndrome subtypes.
  cell_types:
  - preferred_term: Mature neutrophil
    term:
      id: CL:0000096
      label: mature neutrophil
  biological_processes:
  - preferred_term: Neutrophil chemotaxis
    term:
      id: GO:0030593
      label: neutrophil chemotaxis
    modifier: INCREASED
  - preferred_term: Neutrophil migration
    term:
      id: GO:1990266
      label: neutrophil migration
    modifier: INCREASED
  - preferred_term: Neutrophil activation
    term:
      id: GO:0042119
      label: neutrophil activation
    modifier: INCREASED
  downstream:
  - target: Dense Dermal Neutrophilic Infiltrate
    description: >-
      Recruited, activated neutrophils accumulate as a dense sterile infiltrate
      in the dermis.
  evidence:
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      revealing the predominant role of neutrophil activation and abnormal
      proliferation as unifying mechanisms in different SS subtypes
    explanation: >-
      Identifies neutrophil activation and proliferation as the shared
      effector mechanism recruiting neutrophils across subtypes.
- name: Dense Dermal Neutrophilic Infiltrate
  description: >-
    Recruited neutrophils accumulate as a diffuse infiltrate consisting
    predominantly of mature neutrophils in the upper (papillary and reticular)
    dermis, with marked papillary dermal edema and interstitial leukocytoclasis
    (karyorrhectic nuclear debris) but characteristically without true
    leukocytoclastic vasculitis. This sterile dermal infiltrate is the
    histopathologic hallmark and diagnostic core of the disease.
  cell_types:
  - preferred_term: Mature neutrophil
    term:
      id: CL:0000096
      label: mature neutrophil
  downstream:
  - target: Tender Erythematous Plaques and Systemic Inflammation
    description: >-
      The dense dermal neutrophilic infiltrate and accompanying edema manifest
      clinically as tender erythematous plaques with fever and systemic
      inflammation.
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      a diffuse infiltrate consisting predominantly of mature neutrophils that
      are typically located in the upper dermis
    explanation: >-
      Documents the dense mature-neutrophil dermal infiltrate as the
      pathologic hallmark of Sweet syndrome.
- name: Tender Erythematous Plaques and Systemic Inflammation
  description: >-
    The converging neutrophilic dermal process manifests as the clinical
    syndrome: abrupt onset of tender erythematous papules, plaques, and nodules
    accompanied by fever, peripheral neutrophilia, and elevated inflammatory
    markers. Individual lesions are self-limited and typically resolve promptly
    with systemic corticosteroids, though the syndrome frequently recurs.
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      include fever, neutrophilia, tender erythematous skin lesions (papules,
      nodules, and plaques)
    explanation: >-
      Documents the clinical output of the pathophysiologic cascade: fever,
      neutrophilia, and tender erythematous papules/nodules/plaques.

phenotypes:
- category: Clinical
  name: Tender erythematous plaques
  description: >-
    Abrupt onset of tender, edematous, erythematous papules, plaques, and
    nodules is the defining cutaneous feature, favoring the face, neck, chest,
    and extremities.
  phenotype_term:
    preferred_term: Tender erythematous plaque
    term:
      id: HP:0025474
      label: Erythematous plaque
    temporality: ACUTE
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      tender erythematous skin lesions (papules, nodules, and plaques)
    explanation: Documents tender erythematous plaques as the defining cutaneous sign.
- category: Clinical
  name: Cutaneous pustules
  description: >-
    Raised erythematous plaques may show pseudoblistering and occasionally
    develop pustules, part of the "juicy"/pseudovesicular appearance.
  phenotype_term:
    preferred_term: Pustule
    term:
      id: HP:0200039
      label: Pustule
  evidence:
  - reference: PMID:8089280
    reference_title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Raised erythematous plaques with pseudoblistering and occasionally
      pustules occur on the face, neck, chest, and extremities
    explanation: Documents pustules as an occasional cutaneous feature.
- category: Clinical
  name: Fever
  description: >-
    Fever accompanies the eruption and is a diagnostic minor criterion; it
    often precedes or coincides with the skin lesions.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
  evidence:
  - reference: PMID:8089280
    reference_title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      accompanied by fever and general malaise
    explanation: Documents fever accompanying the cutaneous eruption.
- category: Clinical
  name: Malaise
  description: General malaise is a common constitutional symptom accompanying the eruption.
  phenotype_term:
    preferred_term: Malaise
    term:
      id: HP:0033834
      label: Malaise
  evidence:
  - reference: PMID:8089280
    reference_title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      accompanied by fever and general malaise
    explanation: Documents general malaise as a constitutional symptom.
- category: Laboratory
  name: Neutrophilia
  description: >-
    Peripheral blood neutrophilia is a characteristic laboratory finding and a
    diagnostic minor criterion. It is a sterile (reactive) neutrophilia and may
    be absent in malignancy-associated disease with marrow failure.
  phenotype_term:
    preferred_term: Neutrophilia (sterile/reactive)
    term:
      id: HP:0410258
      label: Neutrophilia in absence of infection
  evidence:
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the sudden onset of well-defined tender papules, plaques and nodules
      often accompanied by fever, neutrophilia and elevated markers of
      inflammation
    explanation: Documents neutrophilia as a characteristic laboratory feature.
- category: Laboratory
  name: Leukocytosis
  description: >-
    Leukocytosis (typically with a neutrophil predominance) is part of the
    laboratory diagnostic minor criterion.
  phenotype_term:
    preferred_term: Leukocytosis
    term:
      id: HP:0001974
      label: Increased total leukocyte count
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      include fever, neutrophilia, tender erythematous skin lesions
    explanation: >-
      The neutrophilia documented in the diagnostic constellation reflects the
      leukocytosis with neutrophil predominance seen at presentation.
- category: Laboratory
  name: Elevated inflammatory markers
  description: >-
    Elevated markers of inflammation, including C-reactive protein and
    erythrocyte sedimentation rate, are characteristic and form part of the
    laboratory diagnostic criterion.
  phenotype_term:
    preferred_term: Elevated C-reactive protein
    term:
      id: HP:0011227
      label: Elevated circulating C-reactive protein concentration
  evidence:
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      often accompanied by fever, neutrophilia and elevated markers of
      inflammation
    explanation: Documents elevated inflammatory markers as a characteristic finding.
- category: Laboratory
  name: Elevated erythrocyte sedimentation rate
  description: >-
    An elevated erythrocyte sedimentation rate is one of the laboratory
    abnormalities used as a diagnostic minor criterion.
  phenotype_term:
    preferred_term: Elevated erythrocyte sedimentation rate
    term:
      id: HP:0003565
      label: Elevated erythrocyte sedimentation rate
  evidence:
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      often accompanied by fever, neutrophilia and elevated markers of
      inflammation
    explanation: >-
      Elevated markers of inflammation encompass the elevated erythrocyte
      sedimentation rate used as a diagnostic minor criterion.
- category: Clinical
  name: Arthralgia
  description: >-
    Joint involvement with arthralgia (and sometimes arthritis) is a common
    extracutaneous manifestation. Notably, the ABSENCE of arthralgia is
    statistically associated with underlying malignancy.
  phenotype_term:
    preferred_term: Arthralgia
    term:
      id: HP:0002829
      label: Arthralgia
  evidence:
  - reference: PMID:8089280
    reference_title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Involvement of the eyes, joints, and oral mucosa
    explanation: Documents joint involvement as an extracutaneous manifestation.
  - reference: PMID:29107342
    reference_title: "Sweet syndrome in patients with and without malignancy: A retrospective analysis of 83 patients from a tertiary academic referral center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      absence of arthralgia (P < .001)
    explanation: >-
      Documents that absence of arthralgia is significantly associated with
      malignancy, implying arthralgia is a feature of non-malignant disease.
- category: Clinical
  name: Ocular involvement
  description: >-
    Ocular inflammation, most commonly conjunctivitis (and also episcleritis,
    scleritis, or uveitis), is a recognized extracutaneous manifestation.
  phenotype_term:
    preferred_term: Conjunctivitis
    term:
      id: HP:0000509
      label: Conjunctivitis
  evidence:
  - reference: PMID:8089280
    reference_title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Involvement of the eyes, joints, and oral mucosa
    explanation: Documents ocular involvement as an extracutaneous manifestation.
- category: Clinical
  name: Oral mucosal involvement
  description: >-
    Oral/mucosal lesions (including oral ulceration) occur, and are more common
    in the malignancy-associated form.
  phenotype_term:
    preferred_term: Oral ulcer
    term:
      id: HP:0000155
      label: Oral ulcer
  evidence:
  - reference: PMID:8089280
    reference_title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Involvement of the eyes, joints, and oral mucosa
    explanation: Documents oral mucosal involvement as an extracutaneous manifestation.

biochemical:
- name: Neutrophilia and leukocytosis
  notes: >-
    Peripheral blood neutrophilia and leukocytosis (neutrophils >70%,
    leukocytes >8,000/uL) are characteristic and contribute to the laboratory
    diagnostic criterion; they may be absent in malignancy-associated disease
    with cytopenias.
  evidence:
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      often accompanied by fever, neutrophilia and elevated markers of
      inflammation
    explanation: Documents neutrophilia as a characteristic laboratory abnormality.
- name: Elevated inflammatory markers (ESR/CRP)
  notes: >-
    Elevated erythrocyte sedimentation rate and C-reactive protein are
    characteristic acute-phase abnormalities used in the diagnostic laboratory
    criterion.
  evidence:
  - reference: PMID:39704328
    reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      often accompanied by fever, neutrophilia and elevated markers of
      inflammation
    explanation: Documents elevated inflammatory markers as a laboratory abnormality.

histopathology:
- name: Dense Dermal Neutrophilic Infiltrate Without Vasculitis
  finding_term:
    preferred_term: Dense dermal infiltrate of mature neutrophils without leukocytoclastic vasculitis
    term:
      id: NCIT:C35978
      label: Inflammatory Infiltrate
  diagnostic: true
  description: >-
    The diagnostic histopathologic hallmark is a diffuse dermal infiltrate
    consisting predominantly of mature neutrophils located in the upper dermis,
    with marked papillary dermal edema and interstitial leukocytoclasis
    (karyorrhexis), and characteristically WITHOUT leukocytoclastic vasculitis.
    This dense neutrophilic infiltrate without vasculitis constitutes one of
    the two required major diagnostic criteria and distinguishes Sweet syndrome
    from cutaneous leukocytoclastic vasculitis.
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      a diffuse infiltrate consisting predominantly of mature neutrophils that
      are typically located in the upper dermis
    explanation: >-
      Documents the diagnostic dense dermal mature-neutrophil infiltrate in the
      upper dermis.

diagnosis:
- name: Clinicopathologic diagnostic criteria (major plus minor)
  description: >-
    Diagnosis is clinicopathologic, using the von den Driesch modification of
    the Su and Liu criteria: both major criteria (abrupt onset of tender
    erythematous plaques/nodules; and a dense dermal neutrophilic infiltrate
    without leukocytoclastic vasculitis on biopsy) plus at least two of four
    minor criteria (fever; association with malignancy, inflammatory disease,
    pregnancy, or preceding infection/vaccination; excellent response to
    systemic corticosteroids or potassium iodide; and characteristic laboratory
    abnormalities). Skin biopsy is the cornerstone of diagnosis.
  evidence:
  - reference: PMID:8089280
    reference_title: "Sweet's syndrome (acute febrile neutrophilic dermatosis)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      reviews its epidemiology, clinical spectrum, histologic features,
      laboratory results, differential diagnosis, pathogenic mechanisms,
      associated diseases, and treatment
    explanation: >-
      This foundational review establishes the clinical, histologic, and
      laboratory framework underlying the modified diagnostic criteria.
- name: Work-up for underlying trigger (malignancy, drug, infection)
  description: >-
    Because Sweet syndrome can be paraneoplastic, evaluation should include a
    complete blood count with differential and a search for an underlying
    malignancy (especially acute myeloid leukemia), review of medications
    (notably granulocyte colony-stimulating factor), and assessment for
    infection, inflammatory bowel disease, or autoimmune disease. New or
    recurrent disease, cytopenias, absence of arthralgia, or histiocytoid/
    subcutaneous histology should prompt hematologic evaluation including bone
    marrow examination.
  evidence:
  - reference: PMID:29107342
    reference_title: "Sweet syndrome in patients with and without malignancy: A retrospective analysis of 83 patients from a tertiary academic referral center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      dermatologists should be aware of the potential association of
      leukopenia, anemia, thrombocytopenia, absence of arthralgia, and
      histiocytoid or subcutaneous histopathology with malignancy
    explanation: >-
      Identifies the clinical and laboratory features that should trigger a
      malignancy work-up in Sweet syndrome.

differential_diagnoses:
- name: Pyoderma gangrenosum
  description: >-
    Pyoderma gangrenosum is the other prototypic neutrophilic dermatosis and
    shares pathergy and neutrophilic histology, but produces ulcerating lesions
    with undermined violaceous borders rather than the abrupt tender edematous
    plaques of Sweet syndrome, and both may be paraneoplastic.
  distinguishing_features:
  - "Sweet syndrome: tender edematous erythematous plaques/nodules, dense dermal neutrophilic infiltrate, lesions heal without scarring"
  - "Pyoderma gangrenosum: painful ulcers with undermined violaceous borders, often scarring, strong pathergy"
  disease_term:
    preferred_term: pyoderma gangrenosum
    term:
      id: MONDO:0018824
      label: pyoderma gangrenosum
- name: Cutaneous leukocytoclastic vasculitis
  description: >-
    Cutaneous leukocytoclastic (small-vessel) vasculitis can share neutrophilic
    inflammation and leukocytoclasis, but is defined by true vasculitis with
    fibrinoid necrosis of vessel walls, whereas the defining major criterion of
    Sweet syndrome is a neutrophilic infiltrate WITHOUT leukocytoclastic
    vasculitis.
  distinguishing_features:
  - "Sweet syndrome: dense dermal neutrophils WITHOUT vasculitis, tender plaques/nodules"
  - "Leukocytoclastic vasculitis: fibrinoid necrosis of small-vessel walls, palpable purpura"
  disease_term:
    preferred_term: cutaneous leukocytoclastic angiitis
    term:
      id: MONDO:0019509
      label: cutaneous leukocytoclastic angiitis
- name: Cellulitis / cutaneous infection
  description: >-
    Cellulitis is a frequent clinical mimic because Sweet syndrome plaques are
    tender, erythematous, and febrile, but the Sweet syndrome infiltrate is
    sterile and does not respond to antibiotics, whereas it responds
    dramatically to corticosteroids.
  distinguishing_features:
  - "Sweet syndrome: sterile neutrophilic infiltrate, no response to antibiotics, dramatic corticosteroid response"
  - "Cellulitis: bacterial infection, responds to antibiotics, positive cultures/portal of entry"
  disease_term:
    preferred_term: cellulitis
    term:
      id: MONDO:0005230
      label: cellulitis
- name: Erythema nodosum
  description: >-
    Erythema nodosum is a septal panniculitis producing tender subcutaneous
    nodules on the shins, and like Sweet syndrome is reactive/post-infectious,
    but it lacks the dense dermal mature-neutrophil infiltrate and shows
    granulomatous septal panniculitis instead.
  distinguishing_features:
  - "Sweet syndrome: dermal mature-neutrophil infiltrate, plaques/nodules on face, neck, upper limbs"
  - "Erythema nodosum: septal panniculitis with granulomas, tender nodules on anterior shins"
  disease_term:
    preferred_term: erythema nodosum
    term:
      id: MONDO:0850231
      label: erythema nodosum
- name: Behcet disease
  description: >-
    Behcet disease is a systemic variable-vessel vasculitis on the neutrophilic/
    autoinflammatory spectrum with pathergy and can produce Sweet-like lesions,
    but is defined by recurrent oral and genital ulceration and ocular disease
    with a chronic relapsing multisystem course rather than the abrupt,
    corticosteroid-responsive dermal plaques of Sweet syndrome.
  distinguishing_features:
  - "Sweet syndrome: abrupt tender dermal plaques, dense dermal neutrophils, corticosteroid-responsive"
  - "Behcet disease: recurrent oral and genital ulcers, uveitis, pathergy, chronic relapsing multisystem vasculitis"
  disease_term:
    preferred_term: Behcet disease
    term:
      id: MONDO:0007191
      label: Behcet disease

treatments:
- name: Systemic corticosteroids
  description: >-
    Systemic corticosteroids (e.g., prednisone or prednisolone, roughly
    0.5-1 mg/kg/day tapered over weeks) are the therapeutic gold standard,
    producing a prompt and often dramatic improvement of both the systemic
    symptoms and the skin lesions. Topical or intralesional corticosteroids may
    be used for localized disease.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: prednisone (representative systemic corticosteroid)
      term:
        id: CHEBI:8382
        label: prednisone
    - preferred_term: prednisolone (representative systemic corticosteroid)
      term:
        id: CHEBI:8378
        label: prednisolone
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Systemic corticosteroids are the therapeutic gold standard for Sweet's
      syndrome. After initiation of treatment with systemic corticosteroids,
      there is a prompt response
    explanation: >-
      Establishes systemic corticosteroids as the gold-standard first-line
      treatment with a prompt response.
- name: Potassium iodide
  description: >-
    Potassium iodide is a recognized alternative first-line oral systemic
    agent, useful when corticosteroids are contraindicated.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: potassium iodide
      term:
        id: CHEBI:8346
        label: potassium iodide
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other first-line oral systemic agents are potassium iodide and colchicine.
    explanation: Documents potassium iodide as an alternative first-line oral agent.
- name: Colchicine
  description: >-
    Colchicine is a recognized alternative first-line oral systemic
    anti-inflammatory option and a steroid-sparing choice.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: colchicine
      term:
        id: CHEBI:23359
        label: colchicine
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Other first-line oral systemic agents are potassium iodide and colchicine.
    explanation: Documents colchicine as an alternative first-line oral agent.
- name: Dapsone
  description: >-
    Dapsone is used as a second-line and steroid-sparing systemic agent. Screen
    for glucose-6-phosphate dehydrogenase (G6PD) deficiency before use because
    of hemolysis risk.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: dapsone
      term:
        id: CHEBI:4325
        label: dapsone
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Second-line oral systemic agents include indomethacin, clofazimine,
      cyclosporine, and dapsone.
    explanation: Documents dapsone as a second-line systemic agent.
- name: Treatment of the underlying trigger
  description: >-
    Cause-directed therapy is essential: withdrawing a culprit drug (definitive
    in drug-induced disease), treating the underlying malignancy in
    paraneoplastic disease (Sweet syndrome often remits with tumor control and
    flares with relapse), and managing an underlying infection, inflammatory
    bowel disease, or autoimmune condition.
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Drug-induced Sweet's syndrome (DISS) most commonly occurs in patients who
      have been treated with granulocyte-colony stimulating factor
    explanation: >-
      Documents the culprit-drug (G-CSF) trigger whose withdrawal is the
      definitive treatment of drug-induced disease.

discussions:
- discussion_id: sweet_malignancy_association
  kind: INTERPRETATION
  status: OPEN
  prompt: >-
    How should the paraneoplastic association between Sweet syndrome and
    hematologic malignancy (especially acute myeloid leukemia) be modeled and
    surveilled?
  rationale: >-
    Malignancy-associated Sweet syndrome is a paraneoplastic phenomenon, most
    commonly related to acute myeloid leukemia, and the dermatosis can precede,
    follow, or appear concurrent with the cancer diagnosis. It can therefore be
    the cutaneous harbinger of an occult or recurrent hematologic malignancy.
    This is modeled as a discussion (rather than a fixed structured comorbidity)
    because the relationship is a longitudinal paraneoplastic association that
    mandates malignancy work-up and surveillance, not a simple co-occurrence.
    Features associated with underlying malignancy include cytopenias, absence
    of arthralgia, and histiocytoid or subcutaneous histopathology.
  evidence:
  - reference: PMID:17655751
    reference_title: "Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      MASS can be the cutaneous harbinger of either an undiagnosed visceral
      malignancy in a previously cancer-free individual or an unsuspected cancer
      recurrence in an oncology patient.
    explanation: >-
      Documents malignancy-associated Sweet syndrome as a cutaneous harbinger
      of occult or recurrent malignancy, motivating surveillance.
  - reference: PMID:29107342
    reference_title: "Sweet syndrome in patients with and without malignancy: A retrospective analysis of 83 patients from a tertiary academic referral center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Acute myeloid leukemia was the most common malignancy (in 24 of 83
      patients [29%])
    explanation: >-
      Quantifies acute myeloid leukemia as the most common associated
      malignancy in a Sweet syndrome cohort.
- discussion_id: sweet_epigenetics_metabolomics_gap
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What are the epigenetic, metabolomic, and lipidomic signatures of Sweet
    syndrome, and is there a faithful whole-disease animal model?
  rationale: >-
    The epigenetics, metabolomics, and lipidomics of Sweet syndrome are
    essentially undefined, and there is no single animal model that faithfully
    reproduces the integrated clinical syndrome (acute tender plaques plus fever
    plus corticosteroid responsiveness). Mechanistic understanding rests on
    human cohort, tissue, and in vitro cytokine studies; the pathogenesis is
    explicitly noted to remain incompletely established.
  attaches_to:
  - Cytokine Dysregulation and G-CSF/IL-1 Core

classifications:
  harrisons_chapter:
  - classification_value: DERMATOLOGY
    evidence:
    - reference: PMID:39704328
      reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Sweet syndrome (SS), originally described as acute febrile neutrophilic
        dermatosis, is a rare inflammatory skin condition, considered the
        prototype of neutrophilic dermatoses.
      explanation: >-
        The prototypic neutrophilic dermatosis is a dermatologic inflammatory
        skin condition, supporting a dermatology placement.
  - classification_value: IMMUNE_RHEUMATOLOGIC
    evidence:
    - reference: PMID:39704328
      reference_title: "Molecular Characteristics of Sweet Syndrome: A Systematic Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        recent findings have shed light on the role of dermal infiltrating
        neutrophils-in the context of innate immunity, and signalling pathways
        related to adaptive immunity
      explanation: >-
        The innate/adaptive-immune, autoinflammatory-spectrum pathogenesis
        supports a secondary immune/rheumatologic placement.

notes: >-
  Curation informed by a claude_code deep-research report
  (research/Sweet_Syndrome-deep-research-claude_code.md) used as leads only. All
  evidence snippets were independently verified as exact substrings of cached
  PubMed abstracts. NEC preflight: MONDO:0011959 confirmed via OAK as sweet
  syndrome / acute febrile neutrophilic dermatosis, and the entry is anchored on
  that neutrophilic-dermatosis identity, not on other neutrophilic dermatoses
  (pyoderma gangrenosum) or vasculitides. The deep-research report cited
  PMID:8113453 for the von den Driesch (1994) criteria, but that PMID is
  actually an unrelated epidermolysis-bullosa anesthesia paper (a DR
  misattribution); the correct von den Driesch 1994 review is PMID:8089280,
  which is used here instead. No GeneReviews chapter exists for Sweet syndrome:
  a PubMed "Sweet syndrome GeneReviews[All Fields]" search returns only the
  retired Majeed Syndrome chapter (PMID:20301735, a different MEFV/LPIN2
  autoinflammatory disorder), as expected for a non-Mendelian reactive disorder.
  Sweet syndrome is modeled as a reactive, cytokine-driven neutrophilic
  dermatosis on the autoinflammatory spectrum; no causal Mendelian gene is
  asserted (a rare familial autoinflammatory form and susceptibility signals such
  as MEFV or the VEXAS/UBA1 Sweet-like genocopy exist but are out of scope and
  are not asserted as causal here). Drug (G-CSF) and malignancy (AML) triggers
  are modeled as associations/triggers, not proven single causes. No existing
  mechanism module was a clean fit (the closest, an IL-1/inflammasome or
  neutrophilic-dermatosis module, does not currently exist), so no conforms_to
  is declared.
📚

References & Deep Research

References

5
PMID:14201182
AN ACUTE FEBRILE NEUTROPHILIC DERMATOSIS.
No top-level findings curated for this source.
PMID:17655751
Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis.
No top-level findings curated for this source.
PMID:8089280
Sweet's syndrome (acute febrile neutrophilic dermatosis).
No top-level findings curated for this source.
PMID:29107342
Sweet syndrome in patients with and without malignancy: A retrospective analysis of 83 patients from a tertiary academic referral center.
No top-level findings curated for this source.
PMID:39704328
Molecular Characteristics of Sweet Syndrome: A Systematic Review.
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] 12 citations 2026-07-01T08:50:16.578993

1. Disease Information

Overview. Sweet syndrome (SS), or acute febrile neutrophilic dermatosis, is an uncommon reactive inflammatory (autoinflammatory-spectrum) skin disorder defined by the abrupt onset of tender, edematous, erythematous-to-violaceous papules, plaques, and nodules, typically accompanied by fever, peripheral neutrophilia, and a dense dermal neutrophilic infiltrate on biopsy without leukocytoclastic vasculitis. It responds dramatically to systemic corticosteroids. It was first described by the British dermatologist Robert Douglas Sweet in 1964 (Sweet RD, Br J Dermatol 1964;76:349–356, PMID:14201182).

Key identifiers. - MONDO: MONDO:0011959 (sweet syndrome) — this is the correct MONDO ID for the dismech entry (the template's "MONDO ID: (if available)" field). Related grouping term for neutrophilic dermatoses exists separately. - Orphanet: ORPHA:3243 - MeSH: D016463 (Sweet Syndrome) - ICD-10: L98.2 (Febrile neutrophilic dermatosis [Sweet]) - ICD-11: EB21.1 (Acute febrile neutrophilic dermatosis) - OMIM: 608068 — Sweet syndrome, familial (a rare autosomal-dominant familial form; note that most SS is not Mendelian and has no OMIM number). UMLS: C0085077. - SNOMED CT: 84625002 (Acute febrile neutrophilic dermatosis).

Synonyms / alternative names: acute febrile neutrophilic dermatosis; Gomm-Button disease (historical eponym after Sweet's first two patients); neutrophilic dermatosis, acute febrile. Recognized variants: classical/idiopathic SS, malignancy-associated (paraneoplastic) SS, drug-induced SS; histological/clinical variants include histiocytoid SS, subcutaneous SS (neutrophilic panniculitis), bullous/necrotizing SS, and neutrophilic dermatosis of the dorsal hands.

Data provenance: Aggregated disease-level (Orphanet, OMIM, MeSH, review articles, single-center cohorts). No large EHR/registry-level individual-patient dataset dominates; cohort sizes are typically 50–100 patients.

Sources: Cohen PR, Orphanet J Rare Dis 2007;2:34 (PMID:17655751, PMC1963326); Orphanet ORPHA:3243; MONDO:0011959 (Monarch Initiative).

2. Etiology

Sweet syndrome is best conceptualized as a hypersensitivity/reactive process — an aberrant, cytokine-driven activation and recruitment of neutrophils triggered by an antecedent immunologic stimulus, rather than a primary infection of the skin. The three etiologic settings:

Disease causal factors / triggers by subtype: 1. Classical/idiopathic (~70–80% of cases): Frequently preceded (1–3 weeks prior) by upper respiratory tract or gastrointestinal infection; associated with inflammatory bowel disease (Crohn, ulcerative colitis), autoimmune connective-tissue disease, pregnancy, and vaccination. 2. Malignancy-associated (~15–20%): Paraneoplastic; hematologic malignancy predominates, most commonly acute myeloid leukemia (AML), then myelodysplastic syndrome (MDS); also CML, lymphoma, multiple myeloma; solid tumors (GU, breast, GI) less often. SS may be the presenting sign of an occult hematologic malignancy or herald relapse. 3. Drug-induced: Best-established culprit is granulocyte colony-stimulating factor (G-CSF/filgrastim); also all-trans retinoic acid (ATRA), trimethoprim-sulfamethoxazole and other antibiotics, azathioprine, bortezomib, imatinib, lenalidomide, ipilimumab and other immune-checkpoint inhibitors (e.g., pembrolizumab), hydralazine, furosemide, NSAIDs, oral contraceptives, and certain antiepileptics.

Risk factors. - Environmental/clinical: female sex, age 30–60, antecedent infection, underlying malignancy (esp. myeloid), autoimmune/inflammatory disease, pregnancy, recent culprit-drug exposure. - Genetic/susceptibility: Not a classic monogenic disease. Reported associations/leads: MEFV (Mediterranean fever) variants — a case with compound heterozygous MEFV mutations links SS to the familial-Mediterranean-fever autoinflammatory axis (PMC4599868); HLA associations have been proposed but are inconsistent; rare familial SS (OMIM 608068). A newly recognized major genocopy/mimic is VEXAS syndrome (somatic UBA1 mutation) — see §4.

Protective factors: None specifically established (genetic or environmental). By definition, removal/treatment of the trigger (culprit drug withdrawal, treatment of the underlying malignancy or infection) leads to resolution — the closest analog to a "protective" intervention.

Gene–environment interaction: The prevailing model is that a susceptible host (autoinflammatory predisposition, e.g., inflammasome/IL-1 pathway priming via MEFV variants, or a clonal myeloid population as in VEXAS/MDS/AML) mounts an exaggerated neutrophilic response to an environmental trigger (infection, drug, tumor antigen). This is analogous to a smoke detector wired too hot: the same puff of environmental smoke that a normal system ignores sets off the whole building's alarm.

Sources: PMID:17655751; StatPearls NBK431050; PMC4599868 (MEFV); systematic review PMC11660222.

3. Phenotypes

Below, phenotypes are grouped with suggested HPO terms, typical characteristics, and frequency. Onset is adult (typically 30–60 y); the disease course is acute/episodic with a tendency to recur.

Phenotype (type) HPO suggestion Frequency / characteristics
Tender erythematous papules/plaques/nodules (cutaneous sign) HP:0000988 Abnormal skin morphology / HP:0011123 Inflammatory abnormality of the skin; HP:0200035 Papule; HP:0100650? (plaque) Defining feature; ~100%. Abrupt onset, asymmetric, favoring face, neck, upper limbs; "pseudovesicular"/juicy plaques
Fever HP:0001945 Fever 30–80% (reported "50–80%" classically); often precedes/accompanies eruption
Neutrophilic leukocytosis HP:0011897 Neutrophilia / HP:0001974 Leukocytosis Common (~60–70%); a diagnostic minor criterion; may be absent in malignancy-associated SS with marrow failure
Elevated ESR / CRP HP:0025464 Elevated circulating C-reactive protein concentration; HP:0003565 Elevated erythrocyte sedimentation rate Very frequent; diagnostic minor criterion
Arthralgia / arthritis HP:0002829 Arthralgia / HP:0001369 Arthritis ~30–60%; its absence is associated with malignancy
Ocular involvement (conjunctivitis, episcleritis, scleritis, uveitis) HP:0000509 Conjunctivitis; HP:0100534 (episcleritis); HP:0000554 Uveitis Conjunctivitis most common; broad spectrum incl. peripheral ulcerative keratitis, iritis
Oral/mucosal lesions HP:0000155 Oral ulcer More common in malignancy-associated SS
Pathergy (lesions at trauma sites) HP:0025614? (pathergy) Reported; overlaps with pyoderma gangrenosum
Malaise / headache / myalgia HP:0002027, HP:0002315, HP:0003326 Common constitutional symptoms
Extracutaneous neutrophilic infiltration (see §7) organ-specific HP terms Up to ~50% of cases

Severity/progression: Individual lesions are self-limited but the syndrome is episodic/recurrent (recurrence up to ~50%, higher in malignancy/IBD-associated cases). Lesions heal without scarring (except bullous/ulcerative variants).

Quality-of-life impact: Painful eruptions, fever, and arthralgia impair daily functioning acutely; in paraneoplastic cases the driving concern is the underlying malignancy. No SS-specific validated QoL instrument; generic dermatology tools (DLQI) or SF-36 would apply. Formal QoL data are sparse.

Sources: von den Driesch P, J Am Acad Dermatol 1994 (PMID:8113453); PMID:17655751; PMID:29107342 (83-patient cohort: arthralgia absence, cytopenias associated with malignancy); StatPearls NBK431050.

4. Genetic / Molecular Information

Sweet syndrome is predominantly non-Mendelian; genetics matters chiefly through (a) rare familial forms, (b) autoinflammatory susceptibility genes, and (c) clonal somatic mutations in the malignancy/MDS-associated setting.

Causal / associated genes and variants: - UBA1 (HGNC:12469) — VEXAS syndrome (the transformative recent finding). Somatic mutations at methionine-41 (p.Met41) in UBA1 (X-linked, encoding the E1 ubiquitin-activating enzyme) cause VEXAS (Vacuoles, E1 enzyme, X-linked, Autoinflammatory, Somatic; OMIM 301054), an adult-onset autoinflammatory disease in which Sweet-like neutrophilic dermatosis is the most typical cutaneous histology. Genotype–phenotype: p.Met41Leu carriers frequently show Sweet-like neutrophilic lesions (~82%), whereas p.Met41Val more often gives vasculitic lesions (~55%); the dermal infiltrate is derived from the UBA1-mutated myeloid clone (PMC11170453). Variant type: somatic missense; origin: somatic (acquired, myeloid-restricted); consequence: hypomorphic loss of canonical cytoplasmic UBA1b isoform → activated innate immunity. VEXAS is a critical mimic to exclude in older men with "refractory Sweet syndrome" + macrocytic anemia/cytopenias. - MEFV (HGNC:6998) — pyrin/inflammasome axis. Compound heterozygous MEFV mutations reported in SS, linking it to the familial-Mediterranean-fever/IL-1 autoinflammatory spectrum (PMC4599868). Variant type: missense; origin: germline. - Familial Sweet syndrome (OMIM 608068): rare autosomal-dominant inheritance reported; molecular basis not fully defined. - PIK3R1 (HGNC:8979): a gain-of-function PIK3R1 variant in neutrophils from a refractory-SS patient increased IL-1R1 expression and neutrophil migration (reported in the systematic review PMC11660222) — mechanistic, single-case, functional-genomics lead. - Clonal myeloid drivers (paraneoplastic SS): in AML/MDS-associated SS the skin infiltrate can share cytogenetic/molecular abnormalities of the marrow clone (e.g., trisomy 8 associations with MDS/Behçet-overlap neutrophilic disease); these are somatic and tumor-derived rather than SS-causal per se.

Allele frequencies: UBA1 p.Met41 variants are somatic (absent/negligible in germline gnomAD). MEFV variants (e.g., M694V, V726A) are common founder alleles in Mediterranean populations (gnomAD-documented) but are susceptibility, not causal, for SS.

Modifier genes: none robustly established. Epigenetics: no well-defined DNA-methylation/histone signature specific to SS (a genuine knowledge gap). Chromosomal abnormalities: trisomy 8, del(5q), and other MDS/AML karyotypes appear in the associated hematologic disease.

Suggested annotations: genes HGNC UBA1 (hgnc:12469), MEFV (hgnc:6998), PIK3R1 (hgnc:8979), CSF3/CSF3R (G-CSF axis); GENO for somatic vs germline.

Sources: Beck DB et al. (VEXAS, N Engl J Med 2020, foundational — verify PMID); PMC11170453 (VEXAS skin/genotype); OMIM 301054; PMC4599868 (MEFV); PMC11660222 (PIK3R1, molecular review).

5. Environmental Information

  • Infectious triggers: antecedent upper respiratory tract infection and gastrointestinal infection are the classic prodromes of classical SS (e.g., Streptococcus, Yersinia, Salmonella enterocolitis have been implicated); reported associations with HIV, viral hepatitis, and secondary syphilis. These are triggers, not direct skin pathogens (the infiltrate is sterile). Suggested NCBI Taxonomy anchors only where a specific organism is documented per case.
  • Drug/chemical exposures (see §2): G-CSF is the flagship; also ATRA, TMP-SMX, azathioprine, bortezomib, checkpoint inhibitors, hydralazine, furosemide, minocycline, NSAIDs, oral contraceptives. (CTD-type chemical→disease links.) CHEBI anchors: G-CSF (protein, not CHEBI), all-trans retinoic acid CHEBI:15367, azathioprine CHEBI:2948, bortezomib CHEBI:52717.
  • Lifestyle factors: no established smoking/diet/alcohol causal link. Pregnancy is a recognized (physiologic, not lifestyle) trigger.

Sources: PMID:17655751; StatPearls NBK431050.

6. Mechanism / Pathophysiology

Central causal chain (upstream → downstream):

  1. Trigger / priming (infection antigen, drug, tumor-derived cytokines, or a clonal myeloid population) →
  2. Cytokine dysregulation with a G-CSF and IL-1 core. G-CSF is a "major player" driving neutrophil production, survival, and activation across all three subtypes; serum G-CSF rises in active disease (e.g., 390 pg/mL active vs 14 pg/mL inactive) (PMC11660222). The IL-1β/inflammasome pathway is a key initiating hub — lesional IL-1β transcript up to >250-fold over unaffected skin, though elevation is seen in only a subset of patients (selective inflammasome hyperactivation) (PMC11660222). This is why IL-1 blockade (anakinra) works (PMC3953233).
  3. Th1 / IL-17 skewing. Up-regulation of IL-12, IL-15, interferon-γ (Th1) and the IL-17 axis (IL-17 + receptor, epidermal IL-17E) contributes an adaptive-immune layer (PMC11660222).
  4. Neutrophil chemotaxis and recruitment. IL-6 (up to ~4988 pg/mL in active serum, normalizing after steroids), IL-8/CXCL8, and chemokines CXCL1/2/3 and CXCL16 are overexpressed in lesional tissue, recruiting neutrophils into the dermis (PMC11660222).
  5. Dense sterile dermal neutrophilic infiltration → tissue edema and clinical plaques. Histology: diffuse mature-neutrophil infiltrate in the reticular dermis, marked papillary-dermal edema, and interstitial leukocytoclasis (karyorrhectic nuclear debris), characteristically without true vasculitis (secondary/subtle vascular change may occur). Epidermis usually spared. In the histiocytoid variant, the infiltrate is immature myeloid cells / M2-like CD68+CD163+ macrophages rather than mature neutrophils — important because it mimics leukemia cutis and flags MDS/AML.
  6. Extracutaneous "sterile neutrophilic infiltration" of other organs when systemic (§7).

Cellular processes / GO suggestions: neutrophil chemotaxis (GO:0030593), neutrophil migration (GO:1990266), inflammatory response (GO:0006954), acute inflammatory response (GO:0002526), interleukin-1-mediated signaling (GO:0070498), IL-1β production (GO:0032611), response to granulocyte colony-stimulating factor (GO:0097011), positive regulation of neutrophil activation.

Cell types / CL suggestions: neutrophil (CL:0000775), immature/band neutrophil (CL:0000776), myeloid cell / immature myeloid cell (histiocytoid variant), macrophage (CL:0000235, M2 CL:0000890), dermal microvascular endothelial cell, keratinocyte (bystander).

Immune-system framing: SS sits on the autoinflammatory (innate-immune) spectrum — an aberrant, antigen-nonspecific neutrophil-driven response, overlapping with pyoderma gangrenosum, Behçet disease, and the monogenic autoinflammatory syndromes (hence conceptual dismech links to an inflammasome/IL-1 or neutrophilic-dermatosis module, if one exists or is created).

Protein dysfunction / metabolic changes: In VEXAS, hypomorphic UBA1 loss impairs ubiquitylation → innate-immune hyperactivation and cytoplasmic vacuoles in myeloid precursors. No general SS-wide enzyme deficiency or metabolomic/lipidomic signature is established (knowledge gap).

Sources: Molecular systematic review PMC11660222; Front Immunol 2019;10:414 (Pathogenesis of Sweet's Syndrome — verify PMID); PMC3953233 (anakinra/IL-1); StatPearls NBK431050.

7. Anatomical Structures Affected

Primary organ: skin (UBERON:0002097 skin of body / UBERON:0002067 dermis; reticular dermis UBERON:0004539; papillary dermis UBERON:0004538). Predilection sites: face, neck, upper trunk, upper extremities/dorsal hands; asymmetric; lesions favor sun-exposed/photodistributed and dorsal-hand areas.

Secondary / extracutaneous involvement (up to ~50% of cases) — sterile neutrophilic infiltration of: - Eyes (UBERON:0000970): conjunctivitis, episcleritis, scleritis, uveitis, peripheral ulcerative keratitis. - Musculoskeletal: joints (arthralgia/arthritis), sterile osteomyelitis (bone, UBERON:0002481), muscle (myositis). - Lungs (UBERON:0002048): neutrophilic alveolitis, pleural effusion, culprit of steroid-responsive infiltrates. - Central nervous system (UBERON:0000955 brain / meninges UBERON:0002360): aseptic/neutrophilic meningitis, encephalitis ("neuro-Sweet"). - Heart (UBERON:0000948): myocarditis, aortitis. - Liver (UBERON:0002107), spleen (UBERON:0002106), kidney (UBERON:0002113): sterile neutrophilic infiltration; hepatic/renal involvement reported. - Oral/mucosa, intestine, ears.

Body systems: integumentary (primary); hematologic, ophthalmic, musculoskeletal, respiratory, nervous, cardiovascular, hepatobiliary/GI (secondary).

Subcellular (GO cellular component): no SS-defining organellar lesion; in VEXAS, cytoplasmic vacuoles in myeloid precursors are the hallmark (GO:0005737 cytoplasm).

Lateralization: cutaneous lesions are characteristically asymmetric.

Sources: PMID:17655751; JAAD case/review on extracutaneous SS; StatPearls NBK431050.

8. Temporal Development

  • Onset: adult, peak 30–60 years (classical form 30–50 y in women); pediatric and rare congenital/familial cases exist. Pattern is acute/abrupt ("sudden onset" is a major diagnostic criterion) — lesions erupt over hours to days.
  • Progression / course: individual episodes are self-limited; untreated lesions may persist weeks to months, but respond within days to corticosteroids. Overall course is episodic/relapsing–remitting, especially when tied to an ongoing driver (IBD flare, malignancy relapse, re-exposure to a culprit drug).
  • Remission: frequently treatment-induced (dramatic steroid response); spontaneous resolution occurs, particularly in drug-induced SS after withdrawal of the agent.
  • Recurrence: up to ~50%, higher in malignancy-associated and IBD-associated disease; recurrence should prompt re-evaluation for underlying/occult malignancy.
  • Critical windows: SS as a presenting or relapse marker of hematologic malignancy makes the diagnostic moment a key intervention window — new/recurrent SS warrants CBC/marrow evaluation.

Sources: StatPearls NBK431050; PMID:17655751; cohort PMC10753595 (long-term follow-up, malignancy association, treatment response).

9. Inheritance and Population

Epidemiology: - Prevalence/incidence: true population incidence undefined; considered rare. Institutional data: overall SS incidence ~0.36% among screened populations, rising to ~0.94–1% among AML patients (Karger, Acta Haematol 2024, 28-year AML institutional experience). - Sex ratio: female predominance, classically ~4:1 (F:M) in classical SS; the ratio approaches 1:1 in malignancy-associated SS. - Age distribution: peak 30–60 y; mean age ~50 y in the molecular systematic review cohort (mean 50.7 y; 52% female) (PMC11660222). - Subtype share: classical ~70–80%; malignancy-associated ~15–20% (AML > MDS > other); drug-induced a smaller fraction.

Genetic epidemiology (limited, since mostly non-Mendelian): - Inheritance: predominantly sporadic/multifactorial; rare autosomal-dominant familial SS (OMIM 608068). VEXAS is somatic, X-linked (male-predominant, older men) — not heritable. - Penetrance/expressivity/anticipation/mosaicism: not applicable to the sporadic form; VEXAS is defined by acquired somatic mosaicism in the myeloid lineage. - Founder effects/consanguinity/carrier frequency: relevant only to the MEFV susceptibility axis in Mediterranean populations; no SS-specific carrier screening. - Population/geographic distribution: reported worldwide; no strong ethnic predilection ("no racial predilection" per StatPearls), though some East-Asian/Japanese literature emphasizes SS–MDS and trisomy-8 overlap.

Sources: StatPearls NBK431050; PMC11660222; Karger Acta Haematol 2024;147(4):457; PMID:29107342.

10. Diagnostics

Diagnosis is clinicopathologic, resting on the von den Driesch (1994) modification of the Su & Liu (1986) criteria — both major + ≥2 of 4 minor for classical SS:

Major criteria (both required): 1. Abrupt onset of tender/painful erythematous plaques or nodules. [verify snippet] 2. Histopathology: dense dermal neutrophilic infiltrate without leukocytoclastic vasculitis. [verify snippet]

Minor criteria (≥2 of 4): 3. Fever >38 °C. 4. Association with underlying hematologic/visceral malignancy, inflammatory disease, pregnancy, or preceding respiratory/GI infection or vaccination. 5. Excellent response to systemic corticosteroids (or potassium iodide). 6. Laboratory abnormalities at presentation (≥3 of 4): ESR >20 mm/h; elevated CRP; leukocytosis >8,000; neutrophils >70%.

(Drug-induced SS uses the separate Walker & Cohen 1996 criteria: temporal relation to drug, and resolution on withdrawal / recurrence on rechallenge.)

Laboratory (LOINC-anchorable): CBC with differential (neutrophilia HP:0011897), ESR (LOINC 4537-7), CRP (LOINC 1988-5), often anemia/thrombocytopenia if paraneoplastic. Biopsy is the cornerstone — punch/incisional skin biopsy for H&E (dense dermal neutrophils, papillary edema, leukocytoclasis, no vasculitis) ± immunohistochemistry (MPO+ neutrophils; CD68/CD163 in histiocytoid variant to distinguish from leukemia cutis).

Work-up for underlying cause (mandatory): CBC/peripheral smear, and — given the AML/MDS link — bone marrow examination and cytogenetics if cytopenias, atypical/histiocytoid features, absence of arthralgia, or recurrence; malignancy screening; medication review; infection/IBD/autoimmune evaluation. In refractory or male older-patient cases, sequence UBA1 to exclude VEXAS.

Imaging/other: guided by extracutaneous symptoms (e.g., CXR/CT for pulmonary infiltrates, MRI/LP for neuro-Sweet, echocardiography for myocarditis).

Differential diagnosis: cellulitis/erysipelas (sterile SS mimics infection but doesn't respond to antibiotics), pyoderma gangrenosum, leukocytoclastic vasculitis, erythema nodosum, erythema multiforme, Behçet disease, leukemia cutis, neutrophilic eccrine hidradenitis, VEXAS, bacterial/atypical infection.

Screening: no population screening. Key practical rule: new-onset SS = screen for occult hematologic malignancy, and monitor known MDS/AML patients.

Sources: von den Driesch PMID:8113453; Su & Liu, Cutis 1986 (verify PMID:3527570); Walker & Cohen 1996 (drug-induced criteria — verify PMID); StatPearls NBK431050.

11. Outcome / Prognosis

  • Classical & drug-induced SS: generally excellent prognosis; rapid, often dramatic response to corticosteroids; drug-induced resolves on withdrawal. Lesions heal without scarring (except bullous/ulcerative variants).
  • Recurrence: up to ~50%, especially IBD- or malignancy-associated.
  • Malignancy-associated SS: prognosis is governed by the underlying hematologic disease; SS itself is steroid-responsive but recurs with tumor relapse and may herald progression. Marked cytopenias, absence of arthralgia, and histiocytoid/subcutaneous histology correlate with malignancy (PMID:29107342).
  • Mortality/morbidity: SS is rarely directly fatal; serious morbidity/mortality arise from extracutaneous neutrophilic organ involvement (myocarditis, alveolitis, aseptic meningitis) and from the associated malignancy. Complications: corticosteroid toxicity from prolonged therapy; secondary infection of ulcerated lesions.
  • Prognostic factors: subtype (drug-induced best; malignancy-associated worst), presence/control of underlying malignancy, degree of cytopenia, extracutaneous involvement.
  • QoL: acute pain, fever, arthralgia; generally reversible with treatment. No SS-specific validated instrument.

Sources: PMC10753595 (93-patient long-term cohort); PMID:29107342; StatPearls NBK431050.

12. Treatment

Suggested MAXO anchor for drug therapy: pharmacotherapy (use NCIT:C15986 Pharmacotherapy per dismech convention, with CHEBI therapeutic_agent); MAXO:0000058? (systemic corticosteroid therapy) / MAXO:0000108? — verify exact MAXO IDs with OAK before committing.

First-line: - Systemic corticosteroids — gold standard. Prednisone 0.5–1 mg/kg/day (≈40–60 mg/day) tapered over 2–4 (up to 4–6) weeks; produces rapid defervescence and lesion regression. CHEBI: prednisone CHEBI:8382, prednisolone CHEBI:8378, methylprednisolone CHEBI:6888. Topical/intralesional corticosteroids for localized disease. - Potassium iodide and colchicine (CHEBI:23359) are recognized alternative first-line anti-inflammatory options, useful when steroids are contraindicated. - Dapsone (CHEBI:4325) — first-line/steroid-sparing.

Second-line / steroid-sparing / refractory: methotrexate, cyclosporine, indomethacin, clofazimine, and — for autoinflammatory/refractory disease — biologics targeting the cytokine core: IL-1 blockade (anakinra) with documented efficacy (PMC3953233), TNF inhibitors, and emerging JAK inhibitors — e.g., a 2025 report of Sweet syndrome successfully treated with upadacitinib (PMC12547819).

Cause-directed therapy (essential): - Drug-induced: withdraw the culprit (definitive). - Malignancy-associated: treat the underlying AML/MDS; SS often remits with tumor control and flares with relapse. - Infection/IBD-associated: treat/steroid-manage the underlying condition.

Pharmacogenomics: dapsone carries hemolysis risk in G6PD deficiency — screen before use (a genotype-guided safety step). No SS-specific PGx-guided efficacy markers.

Experimental / trials: IL-1 (anakinra, canakinumab), IL-17, and JAK-pathway agents are the active frontier; check ClinicalTrials.gov for current NCTs (no landmark SS-specific RCT exists — evidence base is case series/cohorts). For VEXAS-driven Sweet-like disease, treatment shifts toward the underlying clone (azacitidine, JAK inhibitors, allogeneic HSCT).

Sources: UpToDate (management); StatPearls NBK431050; Cohen, Sweet's Syndrome: Review of Current Treatment Options (verify PMID); PMC3953233 (anakinra); PMC12547819 (upadacitinib, 2025).

13. Prevention

  • Primary prevention: limited — the disease is reactive. The principal preventable trigger is drug-induced SS: avoid/cautiously monitor known culprits (especially G-CSF, and rechallenge avoidance after a documented episode).
  • Secondary prevention / early detection: recognizing SS as a paraneoplastic sentinel → prompt hematologic work-up enables earlier detection of AML/MDS. Surveillance of MDS/AML patients for cutaneous flares.
  • Tertiary prevention: steroid-sparing maintenance (colchicine, dapsone, methotrexate) to prevent recurrences and limit long-term corticosteroid toxicity; management of the underlying IBD/autoimmune/malignant driver.
  • Immunization/public health/environmental: not applicable (non-infectious, non-communicable).
  • Genetic counseling: relevant only for the rare familial form and for VEXAS (somatic, non-heritable, but with prognostic/therapeutic implications warranting hematology referral).

Sources: PMID:17655751; StatPearls NBK431050.

14. Other Species / Natural Disease

  • Taxonomy: Sweet syndrome is essentially a human (NCBITaxon:9606) diagnosis. There is no well-established naturally occurring homolog in companion animals or wildlife catalogued in OMIA; "sterile neutrophilic dermatosis" and sterile neutrophilic dermatosis/"Sweet's-like" syndromes have been described anecdotally in dogs (canine, NCBITaxon:9615) but are not a defined OMIA Mendelian entry.
  • Orthologous genes: UBA1 and MEFV have clear mammalian orthologs (mouse Uba1, Mefv), enabling mechanistic study of ubiquitylation and pyrin-inflammasome biology, but not disease modeling of SS per se.
  • Comparative biology / evolutionary conservation: the neutrophil-recruitment and IL-1/inflammasome machinery driving SS is deeply conserved across vertebrates, which is why cross-species mechanistic work is informative even without a natural animal counterpart.
  • Zoonotic potential: none (non-infectious).

Sources: OMIA (absence of a defined entry); general veterinary dermatology literature (canine sterile neutrophilic dermatosis, MODEL_ORGANISM/case-level).

15. Model Organisms

Sweet syndrome has no single canonical animal model that faithfully reproduces the full syndrome — a genuine limitation to flag in the dismech entry.

  • Relevant genetic models (mechanism, not whole-disease):
  • UBA1 / VEXAS models: conditional/hematopoietic Uba1 hypomorph and zebrafish uba1 models recapitulate innate-immune hyperactivation and vacuolization, informing VEXAS/Sweet-like neutrophilic dermatosis. (IN_VITRO/MODEL_ORGANISM.)
  • Mefv (pyrin) models: knock-in mice model inflammasome-driven neutrophilic autoinflammation, relevant to the IL-1 axis of SS.
  • G-CSF / CSF3–CSF3R transgenic or administration models: exogenous G-CSF drives neutrophilia and can precipitate neutrophilic-dermatosis-like infiltration, mirroring drug-induced SS.
  • Induced / in vitro models: patient-derived neutrophils and skin explants have been used to demonstrate the IL-1β/G-CSF/IL-8 cytokine profile and the PIK3R1 gain-of-function → enhanced neutrophil migration phenotype (PMC11660222; IN_VITRO). iPSC-derived myeloid systems are a plausible platform for VEXAS-associated neutrophilic dermatosis.
  • Phenotype recapitulation / limitations: models capture components (neutrophilia, IL-1/inflammasome activation, myeloid clonality) but not the integrated clinical syndrome (acute tender plaques + fever + steroid responsiveness). Reactive/paraneoplastic biology is hard to model in a single organism.
  • Resources: MGI (mouse Uba1, Mefv, Csf3/Csf3r), ZFIN (zebrafish uba1), IMPC/IMSR for alleles.

Sources: PMC11660222 (functional neutrophil studies, PIK3R1); VEXAS mechanistic literature; MGI/ZFIN gene records.

Consolidated Evidence Table (top curatable citations)

Claim area Reference ID (verify snippet before commit) Evidence source
Original description; disease definition Sweet RD, Br J Dermatol 1964 PMID:14201182 HUMAN_CLINICAL
Comprehensive review; subtypes; criteria Cohen PR, Orphanet J Rare Dis 2007;2:34 PMID:17655751 (PMC1963326) HUMAN_CLINICAL (review)
Revised diagnostic criteria von den Driesch P, JAAD 1994 PMID:8113453 HUMAN_CLINICAL
Molecular/cytokine mechanisms; PIK3R1; stats Molecular Characteristics of SS: Systematic Review, 2024 PMC11660222 multiple (review)
Malignancy vs non-malignancy features (n=83) Retrospective cohort 2018 PMID:29107342 HUMAN_CLINICAL
93-patient cohort, autoinflammatory/malignancy, follow-up Cohort PMC10753595 HUMAN_CLINICAL
SS in AML, 28-yr institutional (~0.94–1%) Acta Haematol 2024;147:457 Karger (verify PMID) HUMAN_CLINICAL
VEXAS skin manifestations & UBA1 genotype 2024 PMC11170453 HUMAN_CLINICAL
MEFV compound-het in SS Case report PMC4599868 HUMAN_CLINICAL
IL-1 blockade (anakinra) Abstract/report PMC3953233 HUMAN_CLINICAL
JAK inhibitor (upadacitinib) success 2025 PMC12547819 HUMAN_CLINICAL
Clinical overview; epidemiology; treatment dosing StatPearls NBK431050 secondary/reference

Key gaps flagged for the dismech entry

  1. Epigenetics, metabolomics, lipidomics of SS are essentially undefined — mark as KNOWLEDGE_GAP.
  2. No faithful whole-disease animal model — a HUMAN_MODEL_MISMATCH candidate (mechanistic models exist; translational fidelity to the integrated syndrome is unproven).
  3. VEXAS as a molecular genocopy is the most important recent conceptual shift — consider a conforming link between Sweet syndrome and a VEXAS/UBA1 autoinflammatory entry, and an IL-1/inflammasome or neutrophilic-dermatosis mechanism module if one exists or is worth creating.
  4. All snippets marked [verify snippet] are paraphrases and must be replaced with exact abstract quotes via just fetch-reference + just validate-references before committing evidence items.

Sources (primary URLs): - Sweet's syndrome comprehensive review (Cohen 2007, PMC1963326) - Molecular Characteristics of Sweet Syndrome: Systematic Review (PMC11660222) - Sweet Syndrome — StatPearls (NBK431050) - Sweet syndrome in patients with/without malignancy, n=83 (PMID:29107342) - 93-patient cohort with long-term follow-up (PMC10753595) - VEXAS skin manifestations & UBA1 genotypes (PMC11170453) - MEFV compound heterozygous mutations in Sweet's (PMC4599868) - Anakinra for Sweet syndrome (PMC3953233) - Upadacitinib for Sweet syndrome, 2025 (PMC12547819) - SS in AML, 28-year experience (Acta Haematologica 2024) - Orphanet ORPHA:3243 - MONDO:0011959 (Monarch)

A quick note on how to use this, since it feeds a KB: think of Sweet syndrome less like a single broken gene and more like a fire alarm that's wired too sensitive — the neutrophils are the sprinklers, and G-CSF plus the IL-1 inflammasome are the trigger circuit. The cause (infection, drug, or a smoldering myeloid clone) is the smoke. That framing maps cleanly onto a causal chain for the pathophysiology nodes: trigger → G-CSF/IL-1 cytokine surge → chemokine-driven neutrophil recruitment → sterile dermal infiltrate → plaques + fever, with the malignancy-associated arm branching off toward the clonal myeloid/VEXAS biology. Want me to go ahead and draft the actual Sweet_Syndrome.yaml pathophysiology/evidence blocks from this (running the fetch-reference + validation loop as I go), or leave it as the research brief?