Acute Febrile Neutrophilic Dermatosis

(Sweet Syndrome)

ByJulia Benedetti, MD, Harvard Medical School
Reviewed/Revised May 2024
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Etiology of Acute Febrile Neutrophilic Dermatosis

Acute febrile neutrophilic dermatosis may occur with various disorders (see table Disorders and Medications Associated with Acute Febrile Neutrophilic Dermatosis). It is often classified into 3 categories:

  • Classical

  • Cancer-associated

  • Medication-induced

Table

Approximately 20% of patients have an underlying cancer (1), many of which are hematologic cancers, especially myelodysplastic syndromes and acute myelogenous leukemia. The dermatosis often precedes the cancer diagnosis.

Classical acute febrile neutrophilic dermatosis affects mostly women ages 30 to 60. In contrast, men who develop the condition tend to be older.

The cause of acute febrile neutrophilic dermatosis is unknown; however, type 1 helper T-cell cytokines, including interleukin-2 and interferon-gamma, are predominant and may play a role in lesion formation.

Etiology reference

  1. 1. Cohen PR. Sweet's syndrome--a comprehensive review of an acute febrile neutrophilic dermatosis. Orphanet J Rare Dis. 2007;2:34. Published 2007 Jul 26. doi:10.1186/1750-1172-2-34

Symptoms and Signs of Acute Febrile Neutrophilic Dermatosis

Patients are febrile, with an elevated neutrophil count, and have painful, tender, and edematous red to violet nodules or papules, most often on the face, neck, and upper extremities, especially the dorsum of hands. Papules and nodules may coalesce to form plaques. Oral lesions can also occur. The lesions often develop in crops and may appear annular. Each crop is usually preceded by fever and persists for days to weeks. Rarely, bullous and pustular lesions are present as well.

Less common variants include a bullous form that can ulcerate and resemble pyoderma gangrenosum and a subcutaneous form involving the subcutaneous fat that typically has 2- to 3-cm erythematous nodules, commonly affecting the extremities. When on the lower extremities, this form can resemble erythema nodosum.

Acute Febrile Neutrophilic Dermatosis (Sweet Syndrome)
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This photo shows classic erythematous plaques with vesicular borders on the neck and face in a woman with acute febrile neutrophilic dermatosis (Sweet syndrome).
© Springer Science+Business Media

Extracutaneous manifestations are rare and can involve the eyes (eg, conjunctivitis, episcleritis, iridocyclitis), joints (eg, arthralgia, myalgia, arthritis), and internal organs (eg, neutrophilic alveolitis; sterile osteomyelitis; psychiatric or neurologic changes; transient kidney, liver, and pancreatic insufficiency).

Diagnosis of Acute Febrile Neutrophilic Dermatosis

  • Clinical evaluation

  • Skin biopsy

Diagnosis of acute febrile neutrophilic dermatosis is suggested by the appearance of the lesions and is supported by the presence of associated conditions or medications. Differential diagnosis can include erythema multiforme, erythema elevatum diutinum, subacute cutaneous lupus erythematosus, pyoderma gangrenosum, and erythema nodosum.

If the diagnosis is unclear, skin biopsy should be done. The histopathologic pattern is that of edema in the upper dermis with a dense infiltrate of neutrophils in the dermis. Vasculitis may be present but is secondary.

A complete blood count (CBC) is also done. If the CBC is abnormal, bone marrow biopsy should be considered to diagnose occult cancer.

Treatment of Acute Febrile Neutrophilic Dermatosis

  • Systemic corticosteroids

Key Points

  • Acute febrile neutrophilic dermatosis can occur in patients who have certain disorders (classical form) or take certain medications (medication-induced form), but approximately 20% of patients have an underlying cancer (cancer-associated form), usually a hematologic cancer.

  • Diagnose acute febrile neutrophilic dermatosis based on the appearance of the lesions and presence of an associated disorder or medication, and confirm with biopsy when necessary.

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