Abstract

Acute febrile neutrophilic dermatosis (AKA Sweet syndrome) presents clinically as abrupt onset of fever, leukocytosis and erythematous plaques that histologically show superficial dermal infiltration by neutrophils in a bandlike distribution with mild leukocytoclasis. Clinical subtypes include idiopathic/classical, malignancy-associated, and drug-induced.  Classical Sweet syndrome is a relatively rare disease, with a female:male ratio of 1:1, occurring usually in the sixth decade.  Rare, atypical histologic patterns such as histiocytoid, lymphocyte-predominant, and eosinophil-predominant Sweet syndrome also exist. Although eosinophil-predominant cases usually present as drug-induced or malignancy-associated, classical eosinophil-rich Sweet syndrome has also been reported. Here we report a case of an evolving pattern of classical Sweet syndrome in a 45-year-old female who originally presented with erythematous papules and plaques on her extremities and trunk that showed a bandlike neutrophilic infiltrate, small amount of leukocytoclasis, and rare scattered eosinophils and lymphocytes. The patient was started on a prednisone taper and on follow-up showed near complete resolution of symptoms. She then presented seven years later with pseudovesicular plaques on red base and rare pustules on face, trunk, and extremities.  The clinical differential diagnosis was broad and included various viral exanthems. Evaluation of the biopsy showed a superficial neutrophil-rich infiltrate and leukocytoclasis. Additionally, numerous eosinophils were also present throughout the dermis suggesting evolution of the disease to the eosinophilic subtype.  We present this case to illustrate the evolution of classical Sweet syndrome to its rarer, atypical eosinophilic variant as it should be considered in the appropriate clinical context.