Sweet's syndrome (SS), also known as acute febrile neutrophilic dermatosis, is a rare condition characterized by recurrent erythematous skin lesions. Skin lesions appear as papules, nodules and plaques located on the upper extremity, trunk, neck and face.

A 72-year-old male patient presented to the emergency department with a 10-day history of generalized rash, generalized muscle and joint pain and high fever. He had a history of upper respiratory tract infection. He presented with painful erythematous plaques on both lower and upper extremities and the trunk as well as serohemorrhagic bullous lesions on the feet. The laboratory results revealed WBC count of 20.6 × 10³/mm³ (76.9% neutrophils), CRP (c-reactive protein) of 33 mg/L and erythrocyte sedimentation of 110/h. The patient was referred to a dermatologist with prediagnosis of SS due to the presence of typical painful skin lesions, high fever and neutrophilic leukocytosis. A systemic corticosteroid therapy was initiated. The diagnosis for SS was confirmed after the skin biopsy revealed the presence of dense dermal infiltrate of neutrophils and leukocytoclasis in the upper dermis. The patient responded rapidly to corticosteroids and the skin lesions improved.

We reported this case as it was a rare life-threatening dermatosis diagnosed in the emergency department, which is generally difficult to diagnose therein, and the skin lesions appeared on the lower extremities.