Sweet Syndrome

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.

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)

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?