Sweet syndrome (acute febrile neutrophilic dermatosis) is a rare neutrophilic dermatosis characterized by painful erythematous plaques, fever, and neutrophilia. It can be idiopathic, malignancy-associated, or drug-induced. We present a case of Sweet syndrome likely triggered by an inhaled bronchodilator, a previously unreported association, highlighting the importance of considering this diagnosis in patients with sudden-onset cutaneous lesions and systemic symptoms.
#### **Case Presentation**
A 55-year-old woman with a history of hypertension (on enalapril) and COPD (previously on formoterol) presented to primary care with painful erythematous facial and neck plaques and low-grade fever (Fig. 1). The symptoms began two days after switching from formoterol to indacaterol/glycopyrronium inhaler therapy. She denied recent infections, new cosmetics, or dietary changes.
Dermatology evaluation led to discontinuation of the new inhaler, initiation of oral corticosteroids, and biopsy with blood work (revealing leukocytosis, neutrophilia, positive lupus anticoagulant, and negative serology). The lesions improved within 48 hours. Biopsy confirmed Sweet syndrome.
#### **Discussion**
**Diagnostic Criteria & Pathogenesis**
Sweet syndrome is diagnosed based on major criteria (sudden painful plaques, neutrophilic infiltrates on biopsy) and minor criteria (fever, leukocytosis, rapid response to steroids) (Table 1). The etiology remains unclear but may involve cytokine-mediated neutrophil activation triggered by infections, malignancies, or medications (e.g., antibiotics, antihypertensives, contraceptives).
**Drug-Induced Sweet Syndrome**
While inhaled bronchodilators have not been previously implicated, this case suggests a potential association. Given the temporal relationship and exclusion of other triggers, indacaterol/glycopyrronium may have induced a hypersensitivity reaction.
**Differential Diagnoses**
Initial considerations included urticaria, contact dermatitis, toxicoderma, and cutaneous lupus. Histopathology and clinical course confirmed Sweet syndrome.
**Systemic Implications**
Sweet syndrome may signal underlying malignancies (especially hematologic), autoimmune diseases, or infections. Thus, thorough evaluation is essential.
#### **Conclusion**
This case underscores Sweet syndrome as a diagnostic consideration in patients with abrupt-onset painful skin lesions and systemic symptoms, even with uncommon triggers like inhaled medications. Early recognition in primary care ensures prompt referral, biopsy confirmation, and appropriate management, including corticosteroid therapy and investigation for associated systemic conditions.
#### **Ethical Considerations**
Informed consent was obtained, and patient confidentiality was maintained per institutional protocols.
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### **Key Takeaways for Primary Care Physicians**
- Sweet syndrome should be considered in patients with sudden painful erythematous plaques, fever, and neutrophilia.
- Drug-induced cases are rare but possible, even with medications not previously reported.
- Always rule out underlying malignancies, infections, or autoimmune diseases.
- Early referral to dermatology and biopsy are crucial for definitive diagnosis.
- Corticosteroids lead to rapid improvement, reinforcing the diagnosis.
This case highlights the importance of vigilance for rare dermatoses with systemic implications in primary care.
