A Rare Reaction: When an Inhaler Triggers Sweet Syndrome

What started as a routine adjustment in a patient’s COPD inhaler rapidly unfolded into a puzzling medical mystery. Within just two days, a 55-year-old woman developed intensely painful, bright red patches across her face and neck, accompanied by a mild fever.

While the visible symptoms subsided quickly, the biopsy results revealed an unexpected diagnosis—Sweet syndrome, a rare immune-driven skin disorder.

This unusual case may mark the first time an inhaled medication has been linked to this condition, raising new questions about hidden risks in commonly prescribed treatments.

The patient, with a medical history including hypertension and COPD, had been stable on enalapril and formoterol inhaler for years. Due to declining lung function, her pulmonologist switched her inhaler to a combination of indacaterol and glycopyrronium. Just 48 hours after starting the new inhaler, she presented with painful erythematous plaques on her face and neck, plus a low-grade fever. She denied new cosmetic use, diet changes, or cold symptoms but mentioned recent sun exposure with proper protection.

Referred urgently to dermatology, she discontinued the inhaler. Blood tests ruled out infections and autoimmune markers, while a skin biopsy confirmed Sweet syndrome. Oral corticosteroids were prescribed, leading to rapid symptom improvement within two days.

Understanding Sweet Syndrome

Also known as acute febrile neutrophilic dermatosis, Sweet syndrome is characterized by sudden onset of painful, red papules or plaques—often asymmetrical—primarily affecting the face, neck, upper torso, and hands. It typically presents with systemic symptoms such as fever and elevated white blood cells.

While its exact cause remains unclear, Sweet syndrome is believed to stem from cytokine-driven immune responses, triggered by infections, cancers, or certain medications—including antibiotics, antiepileptics, and vaccines. Treatment with corticosteroids usually brings swift relief.

This case stands out because inhaled therapies have never before been documented as a trigger. Differential diagnoses like contact dermatitis, lupus, or urticaria were carefully excluded.

Why This Matters

Sweet syndrome’s rarity and its potential link to serious systemic diseases mean it’s often overlooked in initial diagnoses. This case highlights the critical role primary care providers play in identifying unusual reactions tied to medication changes, ensuring timely referrals and treatment.

Conclusion

This case serves as a reminder that even familiar medications—like inhalers—can occasionally trigger rare, serious immune responses. For clinicians, staying alert to sudden skin changes following medication adjustments is vital. Recognizing atypical causes of Sweet syndrome expands diagnostic awareness and can lead to faster, life-changing interventions.