Febrile Neutrophilic Dermatosis (Sweet's Syndrome)

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• Sweet's syndrome is a dermatologic condition that presents with acute onset of high fever (100.4F), tender nodules and papules with dense neutrophilic infiltrate in the dermis.
  
• It is almost always associated with underlying systemic disease like cancer (acute myelogenous leukemia), infections or immunologic pathology like rheumatoid arthritis.

Pathogenesis

• The pathogenesis of Sweet’s syndrome is not well understood, but it may be a hypersensitivity reaction in which the body’s response to an infection, cancer, or other illness stimulates the production of cytokines, including granulocyte colony-stimulating factor. This process eventually activates neutrophils and promotes abnormal migration of these neutrophils into dermal tissues.
  

Signs and Symptoms

• High fever (>100.4 F)
  
• Tender or painful nodules, papules and plaques on the head, neck, legs, and arms.
• Malaise, arthralgias, myalgias, conjunctivitis or iridocyclitis and headaches

Diagnosis

• Diagnosis is based upon clinical presentation and histological findings.
  
• Histology will show dense neutrophilic infiltrate in the dermis (leukocytoclastic vasculitis must be excluded). The infiltrate is predominantly perivascular with endothelial cell swelling in some vessels. Perivasculitis occurs secondarily, because of cytokines released by the lesional neutrophils. True transmural vasculitis is not an expected finding histopathologically in SS.
• Lab will show elevated ESR (>20mm/hr), elevated CRP, WBC count > 8000 per cubic mm and neutrophils > 70% on peripheral blood smear.

Differential Diagnosis

• Leukocytoclastic vasculitis
  
• Erythema nodusum
  
• Drug reaction
  
• Erythema multiforme
  

Managements

• Drug of choice: Systemic glucocorticoids
  
• Second-line agents are dapsone, colchicine, or potassium iodide
  

Xtra High Yield Point

• On the boards, it is more likely to get case of febrile neutrophilic dermatosis in association with acute myelogenous leukemia or inflammatory diseases like chron's disease or rheumatoid arthritis.
  
• Erythema nodosum typically presents as multiple tender, erythematous nodules or plaques on the lower extremities and typically associated with medications, infections or autoimmune disease. These lesions do not ulcerate and resolves after 2-8 weeks without scarring [ReelDx Patient Video # 1]
• Eryhtema gangrenosum typically presents as hemorrhagic pustules with surrounding erythema that evolves into necrotic ulcers. It is often due to Pseudomonas aeruginosa and occurs most commonly in the setting of profound neutropenia or diabetic patient.

Related ReelDx Video: 

What is the most likely diagnosis? Check out Real Patient Video at ReelDx website

Sweet Syndrome

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Article by: Dr. Chirag Navadia, Founder of MedRX Education and Author of 'Fundamentals of Cardiology'
ReelDx Patient video: James Lace, MD, Childhood health associates of Salem, Tanzania and David Spiro, MD, Co-founder of ReelDx
References: www.nejm.org, www.medscape.com, www.wikipedia.org

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