[A case of Sweet's syndrome (acute febrile neutrophilic dermatosis) associated with mixed connective tissue disease].

Sweet's syndrome (acute febrile neutrophilic dermatosis) is an unusual condition characterized by fever, polymorphonuclear neutrophil leukocytosis of the blood, thick painful plaques on the face, neck and limbs, and a dense dermal infiltrate of mature neutrophils seen histologically. Recently, this disease has also been reported in association with various malignant neoplasms and chronic inflammatory disorders. In the literature, seven cases of Sweet's syndrome associated with collagen diseases have been reported, but no cases with mixed connective tissue disease (MCTD). The first case of Sweet's syndrome associated with MCTD was herein described and discussed. A 49-year-old man was admitted to our hospital with the complaints of high fever and painful erythema on his face, neck and limbs. Six months ago, MCTD was suspected, with the presence of limited cutaneous sclerosis of the hands, Raynaud's phenomenon, polyarthralgia, an elevation of CPK value and a positive anti-RNP antibody. Just before hospitalization, he suffered a prodromal infection of the upper respiratory tract for two weeks. He was diagnosed as Sweet's syndrome by the clinical and histological features. He began receiving corticosteroid therapy (prednisolone 60 mg/day), and within a week he showed dramatic improvement in the above symptoms.