Febrile neutrophilic dermatosis

Overview

Febrile neutrophilic dermatosis, commonly known as Sweet’s syndrome, is a rare inflammatory skin condition characterized by the sudden appearance of painful, red or purple skin lesions, fever, and an elevated neutrophil count. It is classified as a neutrophilic dermatosis because the skin lesions are infiltrated by neutrophils, a type of white blood cell. Sweet’s syndrome can occur on its own (idiopathic), be associated with infections, malignancies (especially hematologic cancers), or be triggered by certain medications.

Causes

Febrile neutrophilic dermatosis can have several underlying causes, and it is often categorized into three main types:

• Classic (idiopathic) Sweet’s syndrome: Occurs without any identifiable cause; may follow an upper respiratory or gastrointestinal infection.

• Malignancy-associated Sweet’s syndrome: Most commonly linked to hematologic cancers, particularly acute myeloid leukemia (AML), but also seen with solid tumors.

• Drug-induced Sweet’s syndrome: Associated with medications such as granulocyte-colony stimulating factor (G-CSF), all-trans retinoic acid (ATRA), and certain antibiotics or NSAIDs.

Symptoms

Sweet’s syndrome typically presents with a combination of cutaneous and systemic symptoms. Common features include:

• Fever: High-grade fever, often preceding or accompanying skin lesions.

• Painful skin lesions: Tender, red or purple papules, nodules, or plaques that may appear on the face, neck, upper limbs, and trunk.

• Lesions with pseudovesicular appearance: Although solid, lesions may appear blister-like due to intense swelling.

• Malaise and fatigue: General feeling of illness.

• Arthralgia or myalgia: Joint or muscle pain in some cases.

• Ocular involvement: Conjunctivitis or episcleritis may occur in a minority of patients.

Diagnosis

Diagnosis of febrile neutrophilic dermatosis is primarily clinical and histological. Key diagnostic steps include:

• Clinical evaluation: Based on the presence of fever, painful skin lesions, and systemic symptoms.

• Skin biopsy: Confirms the diagnosis by showing a dense neutrophilic infiltrate in the dermis without vasculitis.

• Blood tests: Elevated white blood cell count (neutrophilia), elevated erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).

• Investigations for underlying causes: Includes complete blood count, bone marrow biopsy if leukemia is suspected, cancer screening, and a review of medication history.

Treatment

Treatment of Sweet’s syndrome typically leads to rapid improvement. Common therapies include:

• Systemic corticosteroids: Prednisone is the most effective and commonly used treatment; symptoms often resolve within days.

• Alternative medications: For patients who cannot tolerate corticosteroids, options include colchicine, dapsone, potassium iodide, or NSAIDs.

• Treatment of underlying condition: If associated with malignancy or medication, addressing the underlying cause is essential.

• Topical corticosteroids: May be useful in localized or mild cases.

Prognosis

The prognosis of febrile neutrophilic dermatosis is generally favorable, especially in idiopathic cases with prompt treatment. Most patients respond well to corticosteroids, and skin lesions resolve without scarring. However, recurrence is common, especially in cases associated with malignancy or autoimmune diseases. Long-term follow-up is important to monitor for underlying conditions and manage potential relapses.