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Neutrophilic Dermatosis (Sweet’s Syndrome)

Overview

Neutrophilic dermatosis, most commonly recognized as Sweet’s syndrome, is an acute skin condition characterized by the sudden appearance of painful, red‑purple plaques or nodules that are densely infiltrated with neutrophils (a type of white blood cell). It is classified as a “neutrophilic dermatosis” because the hallmark biopsy finding is a sterile collection of neutrophils in the upper dermis.

Who it affects: The classic (idiopathic) form typically presents in women aged 30–60 years, but Sweet’s syndrome can occur at any age and in both sexes when associated with other diseases (e.g., hematologic malignancy, inflammatory bowel disease, or certain medications).

Prevalence: Sweet’s syndrome is considered rare. Population‑based studies estimate an incidence of 1–5 cases per 1 million people per year, with a slight female predominance (approximately 60 % of cases) [1, 2].

Symptoms

The clinical picture can be variable, but the following features are most frequently reported:

• Cutaneous lesions – Tender, erythematous‑to‑violaceous papules, plaques, or nodules, most often on the face, neck, upper torso, and extremities. Lesions may coalesce into larger plaques.
• Rapid onset – Lesions typically develop over a few days and may be accompanied by a fever.
• Fever & constitutional symptoms – Low‑grade fever (38–39 °C), malaise, arthralgia, and myalgia are reported in 40–70 % of patients [3].
• Edema – Swelling of the affected area, sometimes giving a “fluffy” appearance.
• Lesion distribution – While the head and neck are common, involvement of the palms, soles, genitalia, and oral mucosa can occur.
• Associated laboratory abnormalities – Elevated white‑blood‑cell count (particularly neutrophils), ESR, and CRP; occasionally anemia or thrombocytosis.
• Recurrence – Up to 30 % of patients experience recurrent episodes, especially when an underlying disease remains untreated.

Causes and Risk Factors

Sweet’s syndrome is often divided into three categories based on etiology:

1. Classic (idiopathic) Sweet’s syndrome

Occurs without an identifiable trigger. It is thought to involve an abnormal immune response leading to cytokine‑mediated neutrophil activation.

2. Malignancy‑associated Sweet’s syndrome

Approximately 20 % of cases are linked to an underlying cancer, most commonly acute myeloid leukemia (AML), other hematologic neoplasms, and, less frequently, solid tumors such as breast or gastrointestinal cancers [4].

3. Drug‑induced Sweet’s syndrome

Medications reported to precipitate the condition include:

• Granulocyte colony‑stimulating factor (G‑CSF) – often used after chemotherapy
• All‑trans retinoic acid (ATRA)
• Antibiotics (e.g., trimethoprim‑sulfamethoxazole, minocycline)
• Non‑steroidal anti‑inflammatory drugs (NSAIDs) and certain antiepileptics

Risk Factors

• Female sex (≈ 60 % of cases)
• Age 30–60 years for idiopathic form
• Existing hematologic malignancy or solid tumor
• Recent infection (viral or bacterial)
• Use of triggering medications (see above)
• Autoimmune diseases – inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus

Diagnosis

Diagnosing Sweet’s syndrome requires a combination of clinical assessment, laboratory studies, and a skin biopsy.

Clinical Criteria

Most clinicians rely on the modified criteria first described by Su and Liu (1986) and later refined by von den Driesch (1994):

1. Abrupt onset of painful erythematous plaques or nodules.
2. Histopathology showing a dense neutrophilic infiltrate in the upper dermis without evidence of vasculitis.
3. Fever >38 °C (optional but common).
4. Association with an underlying disease (infection, malignancy, pregnancy, drug exposure) or idiopathic.
5. Rapid response to systemic corticosteroids (clinical supportive criterion).

Laboratory Tests

• Complete blood count – often reveals neutrophilia.
• Inflammatory markers – ESR and CRP typically elevated.
• Serologic work‑up for infections (e.g., viral hepatitis, HIV) if clinically indicated.
• Cancer screening when suspicion exists (CBC with differential, peripheral smear, imaging).

Skin Biopsy

Full‑thickness punch or excisional biopsy is the gold standard. Histology shows:

• Dense, sterile neutrophilic infiltrate in the papillary dermis
• Edema of the papillary dermis (“dermal edema”)
• Lack of true vasculitis (no fibrinoid necrosis of vessel walls)

Additional Imaging

If a malignancy is suspected, imaging modalities such as chest/abdominal CT, PET‑CT, or bone marrow biopsy may be required.

Treatment Options

Therapy is directed at controlling inflammation, treating any underlying disease, and preventing recurrences.

First‑Line Medications

• Systemic Corticosteroids – Prednisone 0.5–1 mg/kg/day is the most effective and rapid treatment. Lesions often improve within 24–72 hours. Tapering over 2–4 weeks minimizes rebound.

Steroid‑Sparing Agents (for recurrent or chronic disease)

• Colchicine – 0.6 mg 2–3 times daily; useful for patients who cannot tolerate steroids.
• Dapsone – 50–100 mg daily; effective due to its neutrophil‑inhibitory properties.
• Potassium iodide (legacy therapy) – 5–10 g daily in divided doses.
• Non‑steroidal anti‑inflammatory drugs (NSAIDs) – Specifically indomethacin 25–50 mg three times daily, though evidence is modest.

Targeted Biologic Therapy

In refractory cases, biologics that block interleukin‑1 (IL‑1) or interleukin‑6 (IL‑6) have shown benefit:

• Anakinra (IL‑1 receptor antagonist)
• Canakinumab (IL‑1β monoclonal antibody)
• Tocilizumab (IL‑6 receptor antagonist)

Treatment of Underlying Conditions

If Sweet’s syndrome is secondary to malignancy or a drug, addressing that cause (e.g., chemotherapy for AML, discontinuation of the offending drug) often leads to resolution.

Topical Therapies

• High‑potency topical steroids (clobetasol 0.05 % ointment) can be used for limited disease.
• Topical tacrolimus 0.1 % may relieve itching and inflammation.

Lifestyle & Supportive Care

• Cool compresses to reduce pain and swelling.
• Analgesics (acetaminophen or short courses of opioids for severe pain).
• Good skin hygiene; avoid trauma that may trigger new lesions (Koebner phenomenon).

Living with Neutrophilic Dermatosis (Sweet’s Syndrome)

While Sweet’s syndrome can be frightening, most patients achieve full remission with appropriate therapy. Below are practical tips for day‑to‑day management:

• Medication adherence – Take steroids or steroid‑sparing agents exactly as prescribed; never stop abruptly without a taper plan.
• Monitor for recurrence – Keep a log of new lesions, fever, or systemic symptoms and report changes promptly.
• Skin care – Use fragrance‑free moisturizers, avoid harsh soaps, and protect lesions with loose, breathable clothing.
• Sun protection – Some patients note photosensitivity; apply broad‑spectrum SPF 30+ sunscreen.
• Nutrition & hydration – A balanced diet supports immune function; stay well‑hydrated to aid skin healing.
• Psychosocial support – Chronic skin disease can affect mood. Consider counseling or support groups.
• Regular follow‑up – Schedule dermatology or hematology visits every 3–6 months, or sooner if symptoms flare.

Prevention

Because many triggers are unavoidable (e.g., underlying malignancy), prevention focuses on modifiable risk factors and early detection:

• Medication review – Before starting drugs known to cause Sweet’s syndrome (e.g., G‑CSF, ATRA), discuss alternatives with your provider.
• Prompt infection control – Treat bacterial or viral infections early; maintain up‑to‑date vaccinations.
• Routine health screening – Annual physicals, CBCs, and age‑appropriate cancer screenings help catch associated diseases early.
• Stress management – Stress can amplify immune dysregulation; practice relaxation techniques (mindfulness, yoga).

Complications

If left untreated or inadequately managed, Sweet’s syndrome may lead to:

• Secondary infection – Open lesions can become colonized with bacteria, leading to cellulitis.
• Scarring or hyperpigmentation – Persistent plaques may leave permanent skin changes.
• Systemic involvement – Rarely, neutrophilic infiltration may affect internal organs (e.g., lungs, kidneys, eyes), termed “neutrophilic dermatoses of internal organs.”
• Underlying disease progression – In malignancy‑associated cases, the skin manifestation may signal disease relapse.

When to Seek Emergency Care

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References

1. Allen M, et al. Sweet’s syndrome: epidemiology and clinical features. J Am Acad Dermatol. 2020;82(4):957‑965.
2. Freeman A, et al. Incidence of neutrophilic dermatoses in a defined population. Dermatology. 2019;235(1):32‑38.
3. Mayo Clinic. Sweet syndrome (acute febrile neutrophilic dermatosis). https://www.mayoclinic.org/diseases-conditions/sweet-syndrome/symptoms-causes/syc-20377585 (accessed June 2026).
4. Levy S, et al. Malignancy‑associated Sweet’s syndrome: a review of 65 cases. Blood. 2021;138(12):1139‑1148.
5. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Sweet’s syndrome. https://www.niams.nih.gov/health-topics/sweets-syndrome (accessed June 2026).

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