Sweet's Syndrome Complicated by Kikuchi's Disease and Hemophagocytic Syndrome which Presented with Retinoic Acid-inducible Gene-I in both the Skin Epidermal Basal Layer and the Cervical Lymph Nodes

A 21-year-old man was admitted to our hospital with a fever, erythema, cervical lymphadenopathy and pancytopenia. A diagnosis of Sweet's syndrome (SS) with Kikuchi's disease (KD) and hemophagocytic syndrome (HPS) was made based on the results of a bone marrow aspiration along with the results from biopsy specimens of the brachial skin and a cervical lymph node. The expression of retinoic acid-inducible gene-I (RIG-I) in the skin epidermal basal layer as well as in a cervical lymph node was revealed through immunohistochemistry. He successfully entered remission through treatment with prednisolone. This findings of this case indicate that when SS with KD presents as HPS, it may suggest an association with an RIG-I-related innate immunity.