Atypical Bullous Sweet Syndrome.

Sweet syndrome (acute febrile neutrophilic dermatosis) is characterized by fever, leukocytosis, and tender erythematous skin lesions with neutrophilic infiltrate. Although associated with granulocyte colony-stimulating factor (G-CSF) use, its occurrence with pegfilgrastim-the pegylated form-is rare, with fewer than five reported cases. Sweet syndrome has also been rarely linked to FLT3 inhibitors such as quizartinib. We report a 71-year-old male with acute myeloid leukemia who developed bullous Sweet syndrome following concurrent exposure to pegfilgrastim and quizartinib.