Rare skin diseases are of great interest to dermatologists. Sweet's syndrome (also known as acute febrile neutrophilic dermatosis) is among them. The article presents an overview of the etiology, clinical and pathomorphological diagnostic criteria, differential diagnosis, and treatment of patients with this disease. The authors report their own clinical observation of Sweet's syndrome in a 57-year-old woman. The diagnosis was made on the basis of medical history, clinical findings, the results of dermoscopy and the course of the disease. Administration of systemic gluocorticosteroid resulted in complete regression of rash. The authors emphasize that the correct diagnosis made by dermatologist facilitated rapid remission of the skin process and well-timed visiting of other medical specialists (primary care physician, infectious disease specialist, rheumatologist, oncologist) and identifying serious somatic pathology or cancer.