Sweet syndrome: an update on clinical aspects, pathophysiology, and treatment

Sweet syndrome is a neutrophilic dermatosis characterized by an autoinflammatory nature and a sterile neutrophilic infiltrate. It presents with tender, erythematous, edematous papules or plaques, often accompanied by fever. Aim of this review is to summarize the most meaningful aspects of Sweet syndrome, critically discussing old paradigms and novel findings. A search of the English-language literature was conducted using the terms "Sweet syndrome" and "acute febrile neutrophilic dermatosis." MEDLINE (via PubMed) and Web of Science (WOS) databases were consulted up to June 30, 2024. Since its first identification, new clinical and histopathological variants of Sweet syndrome have been described, highlighting its heterogeneity. Additionally, a multitude of clinical conditions have been increasingly reported in association with Sweet syndrome, ranging from malignancies, autoimmune and infectious disorders. The pathogenesis of the disease is unclear and varies according to the associated conditions. One unifying mechanism is the aberrant activation, proliferation, and skin homing of neutrophils. The mainstay of treatment remains systemic corticosteroids; alternatives include colchicine, dapsone, and potassium iodide. Traditional immunosuppressants, biologic agents, and small molecules have also been described as effective in treating Sweet syndrome. Sweet syndrome is a heterogeneous condition with an elusive pathogenesis. Most cases resolve with corticosteroids, but some remain refractory to various therapies, representing an unmet medical need. Recent evidence on the pathomechanisms underlying Sweet syndrome suggests that not only innate but also adaptive immunity might play roles. Further experimental studies are needed and may help identify new therapeutic targets in the future.