What are the clinical manifestations of Sweet syndrome (Acute Febrile Neutrophilic Dermatosis) and its differential diagnoses?

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Last updated: May 29, 2025 • View editorial policy

From the Guidelines

Sweet syndrome, also known as acute febrile neutrophilic dermatosis, typically presents with sudden onset of tender, erythematous papules, plaques, or nodules that may have a pseudovesicular appearance, and its clinical manifestation and differential diagnoses should be carefully evaluated to ensure proper treatment and management. The clinical manifestations of Sweet syndrome include tender, red inflammatory nodules or papules, usually affecting the upper limbs, face or neck, as described in the study by 1. Key features of Sweet syndrome include:

  • Sudden onset of tender, erythematous papules, plaques, or nodules
  • Lesions commonly appear on the face, neck, upper extremities, and trunk
  • Often accompanied by fever, malaise, and arthralgia
  • Laboratory findings frequently include leukocytosis with neutrophilia, elevated inflammatory markers (ESR, CRP), and a skin biopsy showing dense neutrophilic infiltrates in the dermis without vasculitis
  • Can be idiopathic or associated with malignancy (particularly hematologic), inflammatory conditions, medications, or infections

Differential diagnoses for Sweet syndrome include:

  • Erythema multiforme
  • Cellulitis
  • Pyoderma gangrenosum
  • Leukocytoclastic vasculitis
  • Erythema nodosum
  • Neutrophilic dermatoses like pustular psoriasis As recommended by 2 and 3, a skin biopsy or aspiration of the lesion to obtain material for histological and microbiological evaluation should always be implemented as an early diagnostic step to differentiate Sweet syndrome from other conditions. Treatment typically involves systemic corticosteroids, which usually produce rapid improvement, as noted in the study by 1. Alternative therapies include colchicine, dapsone, potassium iodide, or immunosuppressants like cyclosporine for refractory cases. When Sweet syndrome is associated with an underlying condition, treating that condition is essential for complete resolution, as emphasized by 4. The pathophysiology involves cytokine dysregulation leading to neutrophil activation and infiltration, though the exact trigger varies depending on the underlying cause.

From the Research

Clinical Manifestation of Sweet Syndrome

  • Sweet syndrome is characterized by a constellation of clinical symptoms, physical features, and pathologic findings which include fever, neutrophilia, tender erythematous skin lesions (papules, nodules, and plaques), and a diffuse infiltrate consisting predominantly of mature neutrophils that are typically located in the upper dermis 5.
  • The syndrome presents with tender, erythematous, edematous papules or plaques, often accompanied by fever 6.
  • Sweet syndrome can also present with extra-cutaneous manifestations 7.

Classification of Sweet Syndrome

  • Sweet syndrome can be classified based upon the clinical setting in which it occurs: classical or idiopathic Sweet's syndrome, malignancy-associated Sweet's syndrome, and drug-induced Sweet's syndrome 5, 7.
  • Classical Sweet's syndrome (CSS) usually presents in women between the age of 30 to 50 years, it is often preceded by an upper respiratory tract infection and may be associated with inflammatory bowel disease and pregnancy 5.
  • Malignancy-associated Sweet's syndrome (MASS) can occur as a paraneoplastic syndrome in patients with an established cancer or individuals whose Sweet's syndrome-related hematologic dyscrasia or solid tumor was previously undiscovered 5.
  • Drug-induced Sweet's syndrome (DISS) most commonly occurs in patients who have been treated with granulocyte-colony stimulating factor, however, other medications may also be associated with DISS 5.

Differential Diagnosis

  • Other dermatologic conditions can present with similar clinical and histological features, therefore, diagnostic criteria are important for the correct diagnosis of Sweet syndrome 8.
  • Conditions that may be considered in the differential diagnosis of Sweet syndrome include other neutrophilic dermatoses, infectious diseases, and inflammatory disorders 6, 9.

Treatment Options

  • Systemic corticosteroids are the therapeutic gold standard for Sweet's syndrome 5, 7, 6.
  • Other treatment options include topical and/or intralesional corticosteroids, potassium iodide, colchicine, indomethacin, clofazimine, dapsone, and cyclosporine 5, 7, 8.
  • Traditional immunosuppressants, biologic agents, and small molecules have also been described as effective in treating Sweet syndrome 6.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Sweet syndrome: an update on clinical aspects, pathophysiology, and treatment.

Italian journal of dermatology and venereology, 2024

Research

Sweet's syndrome: a review of current treatment options.

American journal of clinical dermatology, 2002

Research

Sweet syndrome: acute febrile neutrophilic dermatosis.

Seminars in dermatology, 1995

Research

Sweet Syndrome: A Review of Published Cases.

Dermatology (Basel, Switzerland), 2023

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.