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Acute febrile neutrophilic dermatosis in Adult
See also in: Cellulitis DDx
Other Resources UpToDate PubMed

Acute febrile neutrophilic dermatosis in Adult

See also in: Cellulitis DDx
Contributors: Erin X. Wei MD, Tyler Werbel MD, Andrew Walls MD, Belinda Tan MD, PhD, Susan Burgin MD
Other Resources UpToDate PubMed


Acute febrile neutrophilic dermatosis, also known as Sweet syndrome, is an inflammatory disorder manifesting as multiple sterile, painful, edematous, erythematous plaques that are usually associated with fever and leukocytosis. The disease is typically limited to the skin, although any organ system may also be affected.

Sweet syndrome is classified by etiology:
  • Classic idiopathic
  • Pregnancy-associated
  • Parainflammatory
  • Paraneoplastic
  • Drug-associated
A recent classification contracts this as follows:
  • Classic (includes all inflammatory causes including infection, inflammatory bowel disease [IBD], and pregnancy)
  • Paraneoplastic and drug-related
Sweet syndrome may be seen in patients of all ages, but it is most common in healthy women aged 20-60 years and individuals with IBD or hematologic malignancies (especially myeloid leukemias and myelodysplastic syndrome). Other common associations include pregnancy, streptococcal pneumonia, autoimmune disorders, radiation therapy, lymphedema, and medications (sulfamethoxazole-trimethoprim, minocycline, granulocyte colony-stimulating factor). While most cases are idiopathic or associated with benign conditions, about 15%-20% are associated with malignancy. Sweet syndrome can proceed a diagnosis of malignancy by up to several months. Most common malignancies are hematologic.

Although the exact etiology is still unclear, abnormal cytokine expression and atypical neutrophil function are thought to contribute to the pathogenesis. A genetic predisposition may also contribute.

Pathergy is reported in a minority of adult cases. When present, lesions arise or worsen in sites of cutaneous injury, such as needle sticks. Extracutaneous manifestations such as fever, headaches, myalgias, malaise, arthralgias, and ocular inflammation may be seen. Other sites that may rarely be affected include the oral mucosa, liver (hepatitis), kidney (acute renal failure), lungs (pulmonary abscess and infiltrate), heart (pericarditis, aortitis), central nervous system (CNS) (encephalitis), gastrointestinal (GI) tract (ileitis), lymphatics (lymphadenitis), musculoskeletal (myositis), and bones (sterile osteomyelitis). Hypotension and tachycardia are rare but can occur as a result of systemic inflammation.

Neutrophilic dermatosis of the dorsal hands is considered by many to represent a localized form of Sweet syndrome. Hematologic malignancies and IBD are the most common associations with this subtype.

Necrotizing neutrophilic dermatosis describes a subset of patients with severe Sweet syndrome or pyoderma gangrenosum who develop, in addition to their cutaneous disease, fever, leukocytosis (or a leukemoid reaction), and features of shock. Skin pain is a prominent symptom. Additionally, soft tissues underlying areas of skin involvement may be affected with neutrophilic infiltrates and necrosis.

Sweet syndrome typically responds rapidly to systemic corticosteroids, but recurrences can be seen in up to a third of affected individuals.


L98.2 – Febrile neutrophilic dermatosis [Sweet]

84625002 – Acute febrile neutrophilic dermatosis

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

  • Pyoderma gangrenosum – Begins as a pustule and evolves into a purulent ulcer with rolled borders. Has similar associations, including IBD and malignancy.
  • Neutrophilic eccrine hidradenitis – Drug-induced toxicity of the eccrine coils 1-2 weeks following chemotherapy. Palmar involvement is more suggestive of this diagnosis. Patients typically lack fevers, but pathology may be required to differentiate these entities.
  • Rheumatoid neutrophilic dermatosis
  • Bowel-associated dermatosis-arthritis syndrome – Pustular skin lesions and aseptic arthritis in bowel-bypass patients.
  • Eosinophilic cellulitis – Involved skin is typically neither tender nor warm. Eosinophilia is present in 50% of affected individuals; neutrophilia would be unusual. Eosinophils and flame figures can be seen on pathology.
  • Necrotizing fasciitis – Necrotizing neutrophilic dermatosis may mimic necrotizing fasciitis. Histopathologic findings and blood and tissue cultures are useful diagnostically.
  • Erythema multiforme – Should display classic target lesions with 3 zones of color; favors acral surfaces. Oral involvement is common.
  • Azathioprine hypersensitivity syndrome – Acute neutrophilic and systemic reaction after initiating azathioprine. See Drug-induced hypersensitivity syndrome.
  • Urticarial vasculitis
  • Erythema elevatum diutinum – A form of chronic necrotizing vasculitis that primarily involves extensor surfaces.
  • Cutaneous small vessel Vasculitis – Presents symmetrically on the lower extremities; typically smaller than the plaques of Sweet syndrome.
  • Behçet syndrome – Rare, recurrent, and associated with oral or genital ulcers.
  • Bromoderma or Iododerma
  • Bacterial infections (Furunculosis, Cellulitis)
  • Sporotrichosis
  • Mycobacteria spp infections (typical and Atypical mycobacterial infection), including Mycobacterium marinum infection
  • Erythema nodosum – Primarily over the shins.
  • Cutaneous leishmaniasis – Recent travel to endemic areas.
  • Lymphoma / Leukemia cutis
  • Metastatic cutaneous carcinoma
  • Majocchi granuloma
  • Sarcoidosis
  • Orf
  • Cat-scratch disease
  • Cutaneous anthrax
  • Coccidioidomycosis
  • VEXAS syndrome

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Management Pearls

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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Last Reviewed:12/05/2022
Last Updated:07/18/2023
Copyright © 2024 VisualDx®. All rights reserved.
Acute febrile neutrophilic dermatosis in Adult
See also in: Cellulitis DDx
A medical illustration showing key findings of Acute febrile neutrophilic dermatosis : Fever, Asymmetric trunk or extremity distribution, Painful skin lesions, CRP elevated, ESR elevated, WBC elevated, Smooth nodules, Smooth plaques
Clinical image of Acute febrile neutrophilic dermatosis - imageId=1858339. Click to open in gallery.  caption: 'A well-demarcated, deep pink, pseudovesicular plaque over the medial clavicle.'
A well-demarcated, deep pink, pseudovesicular plaque over the medial clavicle.
Copyright © 2024 VisualDx®. All rights reserved.