Skin nontumor

Dermal non-granulomatous granulocyte-rich reaction patterns

Sweet syndrome

Last author update: 1 August 2011
Last staff update: 17 July 2020

Copyright: 2002-2023,, Inc.

PubMed Search: Sweet syndrome [title]

Mowafak Hamodat, M.B.Ch.B., M.Sc.
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Cite this page: Hamodat M Sweet syndrome. website. Accessed March 24th, 2023.
Definition / general
  • Also called acute febrile neutrophilic dermatosis
  • Abrupt onset of tender or painful erythematous plaques and nodules on the face and extremities and less commonly on the trunk, in association with fever (usually), malaise and a neutrophil leukocytosis
  • Associated with AML, less often with solid malignancies
  • Often females, any age but rare in childhood
  • Unknown etiology, but may represent immunological hypersensitivity reaction
  • Most cases respond to oral corticosteroids
  • Thalidomide was successful in one patient who failed to respond to metronidazole, dapsone and methotrexate; IV immunoglobulin was used in a child with concurrent immunodeficiency
  • Also response to 5-azacytidine in patient with myelodysplastic syndrome
  • A case of histiocytoid Sweet's syndrome was responsive to dapsone; dapsone has also been used with systemic corticosteroids in a patient who was HIV positive
Microscopic (histologic) description
  • Intense neutrophilic dermal infiltrate in reticular dermis, may be perivascular, diffuse and surround sweat glands; edema with marked leukocytoclasia; marked papillary edema
  • Occasional presence of dermal papillary microabscesses can result in confusion with dermatitis herpetiformis
  • Epidermis is normal, occasionally slight spongiosis, vesiculation with spongioform pustule
  • Necrotic keratinocytes may be present
  • Variable eosinophils, lymphocytes and histiocytes
  • Blood vessels are dilated and show endothelial swelling
Microscopic (histologic) images

Contributed by Angel Fernandez-Flores, M.D., Ph.D.

Differential diagnosis
  • Behçet disease may be associated with lesions similar to Sweet syndrome
  • Gram stain and PAS exclude infection
  • Granuloma faciale: fibrinoid necrosis is minimal but eosinophils are prominent
  • Late lesions of erythema elavatum diutinum and granuloma faciale show fibrosis, not seen in Sweet Syndrome
  • Pyoderma gangrenosum: has ulcer, no leukorrhexis
  • Rheumatoid neutrophilic dermatitis, neutrophil rich variant of anaplastic large cell lymphoma
  • Presence of fibrinoid vascular changes distinguishes necrotizing vasculitis such as leukocytoclastic vasculitis, erythema elevatum diutinum and granuloma faciale from Sweet syndrome
Additional references
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