This case centers on a 55-year-old woman with a known medical history of hypertension and chronic obstructive pulmonary disease (COPD), conditions that had been stable for years under regular treatment with enalapril and the long-acting bronchodilator formoterol. Her clinical course took an unexpected turn shortly after a modification in her respiratory therapy. Following the introduction of a new inhaled combination—indacaterol with glycopyrronium—she developed a sudden and alarming dermatological reaction.
Within days of initiating the new medication, the patient presented with intensely painful, erythematous lesions involving her face and neck, accompanied by a persistent low-grade fever. The lesions were tender, inflamed, and rapidly progressive, prompting concern from both the patient and her care team. Importantly, she denied any recent changes in cosmetics, skincare products, or diet, and reported no symptoms suggestive of an acute infection or recent illness—details that helped narrow the diagnostic possibilities.
Given the severity and rapid onset of symptoms, an urgent dermatological evaluation was requested. Clinicians immediately suspected a drug-related reaction and discontinued the newly prescribed inhaled therapy. Oral corticosteroids were initiated without delay. Laboratory investigations revealed marked leukocytosis with neutrophilia, consistent with an inflammatory process, while serological testing for infectious and autoimmune markers returned negative.
The patient’s response to treatment was swift and reassuring. Within 48 hours of stopping the suspected medication and starting corticosteroid therapy, both her systemic symptoms and skin lesions began to markedly improve. A skin biopsy was performed to confirm the diagnosis, and histopathological analysis revealed dense neutrophilic infiltration of the dermis—findings diagnostic of Sweet syndrome.
Sweet syndrome, also known as acute febrile neutrophilic dermatosis, is a rare inflammatory condition characterized by the sudden appearance of painful, erythematous plaques or nodules, often accompanied by fever and elevated inflammatory markers. Histologically, it is defined by prominent neutrophil infiltration without evidence of infection. While the syndrome is most commonly associated with infections, malignancies (particularly hematologic cancers), autoimmune disorders, and certain medications, drug-induced Sweet syndrome remains relatively uncommon.
Notably, although medication-related cases are reported more frequently in women, there have been no previous documented cases directly linking Sweet syndrome to inhaled bronchodilators such as indacaterol or glycopyrronium. This makes the present case particularly significant, expanding the spectrum of potential pharmacologic triggers clinicians should consider.
A comprehensive differential diagnosis was carefully explored. Conditions such as urticaria, allergic or contact dermatitis, toxic drug eruptions, and cutaneous lupus erythematosus were evaluated but ultimately ruled out based on clinical presentation, laboratory findings, histopathology, and the patient’s rapid response to corticosteroids.
This case highlights a critical lesson for primary care physicians and frontline clinicians: rare dermatoses should remain on the diagnostic radar when evaluating adverse drug reactions, even when medications are commonly prescribed and generally well tolerated. Early recognition of Sweet syndrome is essential, as prompt treatment leads to rapid symptom resolution and prevents unnecessary morbidity. Equally important is the need for thorough systemic evaluation once the diagnosis is established, given the potential association with underlying malignancies or autoimmune diseases.
In this instance, timely intervention, interdisciplinary collaboration, and a high index of suspicion allowed for an accurate diagnosis and favorable outcome—underscoring the value of vigilance in clinical practice when new therapies are introduced.
