Painful indurated erythema suggestive of Kikuchi-Fujimoto disease in a patient with primary Sjögren's syndrome.

We report a patient with primary Sjögren's syndrome who developed pyrexia, cervical lymphadenopathy, and painful indurated erythema on the forehead, back, chest, abdomen, and limbs. Laboratory data showed an elevated erythrocyte sedimentation rate, C-reactive protein and CH50 in addition to existing autoantibodies including anti-nuclear antibody, anti SS-A antibody, and anti SS-B antibody. A skin biopsy specimen showed focal infiltration of histiocytes with non-neutrophilic karyorrhetic debris in the dermis and subcutaneous fat tissue. Immunohistochemically the infiltrated cells were stained for CD68, suggesting cutaneous involvement of Kikuchi-Fujimoto disease. All symptoms and laboratory data improved within three weeks after treatment with 20 mg/day of prednisolone. The present case suggests that a pathophysiological condition similar to Kikuchi-Fujimoto disease can develop during the long-term course of Sjögren's syndrome.