Definition and epidemiology
Sweet syndrome — acute febrile neutrophilic dermatosis — is a reactive inflammatory disorder defined by the abrupt onset of tender erythematous plaques, fever, and a dense dermal neutrophilic infiltrate without vasculitis. It is uncommon in childhood (roughly 5–8% of cases) and is conventionally split into three subtypes: classical/idiopathic (often post-infectious, especially upper-respiratory or gastrointestinal infection), malignancy-associated (in children chiefly haematological — leukaemia, myelodysplasia), and drug-induced (G-CSF, all-trans retinoic acid, certain antibiotics). A distinct neonatal/infantile presentation and association with immunodeficiency and autoinflammatory syndromes are recognised. Skewed female predominance seen in adults is less marked in children.
Clinical features
Onset is abrupt. Lesions are tender, sharply demarcated, juicy red-to-violaceous plaques, nodules, or pseudovesicles, typically on the face, neck, and upper limbs, sometimes with pustules, bullae, or a targetoid appearance; pathergy (lesions at sites of trauma) may occur. High fever and malaise are usual, and an elevated neutrophil count and acute-phase response are characteristic. Extracutaneous (neutrophilic) involvement — ocular (conjunctivitis, episcleritis), musculoskeletal (arthralgia, arthritis), pulmonary, hepatic, and CNS — can occur and is more concerning in children. Mucosal lesions, though rare, are described.
Diagnosis
Diagnosis rests on the von den Driesch (1994) criteria: both major criteria plus two of four minor criteria establish classical or malignancy-associated Sweet syndrome. The major criteria are (1) abrupt onset of tender/painful erythematous plaques or nodules and (2) a histology of dense dermal neutrophilic infiltrate without leucocytoclastic vasculitis — the histological cornerstone. The minor criteria are (1) fever > 38 °C; (2) association with an underlying haematological/visceral malignancy, inflammatory disease, pregnancy, or antecedent respiratory/GI infection or vaccination; (3) excellent response to systemic corticosteroids (or potassium iodide); and (4) abnormal labs at presentation — three of four of ESR > 20 mm/h, raised CRP, leucocytosis > 8,000, and neutrophils > 70%. Drug-induced Sweet syndrome uses a separate five-item set requiring a temporal drug relationship and resolution on withdrawal. Skin biopsy is essential to confirm the infiltrate and exclude infection and vasculitis. In every child, screen for an underlying trigger — including a haematological workup for occult malignancy.
See the full criteria: Sweet Syndrome Criteria
Red flags
- Sweet syndrome without an obvious infectious/drug trigger — investigate for occult haematological malignancy (leukaemia, MDS).
- Recurrent or treatment-resistant disease — re-evaluate for underlying systemic disease.
- Rapidly necrotic or ulcerating lesions — consider pyoderma gangrenosum overlap or alternative diagnosis.
- Ocular pain/visual change, breathlessness, or neurological signs — extracutaneous neutrophilic involvement.
- Neonatal/infantile presentation — consider underlying immunodeficiency or autoinflammatory disorder.
Management overview
First, identify and treat the trigger — withdraw a culprit drug, treat the precipitating infection, and evaluate for malignancy. Systemic corticosteroids are the mainstay and produce a dramatic, often diagnostic, response with rapid defervescence and lesion resolution; a gradual taper limits relapse. For localised disease, potent topical or intralesional corticosteroids may suffice. Steroid-sparing or recurrent disease is managed with first-line alternatives such as potassium iodide, colchicine, or dapsone; refractory cases may need other immunomodulators or biologics. Doses are deliberately omitted here — verify weight-based regimens against current guidance. Most children respond well with a good prognosis, but malignancy-associated disease follows the course of the underlying condition.
References
- von den Driesch P. Sweet’s syndrome (acute febrile neutrophilic dermatosis). J Am Acad Dermatol. 1994;31(4):535-556.
- Cohen PR. Sweet’s syndrome — a comprehensive review. Orphanet J Rare Dis. 2007;2:34.
- Halpern J, Salim A. Pediatric Sweet syndrome. Pediatr Dermatol. 2009;26(4):452-457.
- Nelson Textbook of Pediatrics, 21st ed.
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.