Subcutaneous sweet syndrome.

Neutrophilic panniculitis encompasses a heterogeneous group of diseases histopathologically characterized by an inflammatory infiltrate in the subcutaneous fat mainly composed of mature neutrophils. This group of panniculitides includes alpha(1)-antitrypsin deficiency, infectious panniculitis, factitious panniculitis, subcutaneous Sweet syndrome, neutrophilic/pustular panniculitis associated with rheumatoid arthritis, erythema nodosum-like lesions of Behçet disease, bowel bypass panniculitis, and iatrogenic panniculitis. This article reviews subcutaneous Sweet syndrome, which is a rare idiopathic panniculitis characterized by a dense neutrophilic infiltrate in the subcutis and is often related to hematologic malignancies. The relationship of subcutaneous Sweet syndrome and erythema nodosum is discussed as well as the differential diagnosis with other neutrophilic panniculitis.