Coincident Kikuchi-Fujimoto's disease and adult-onset Still's disease: report of a patient from an uncommonly affected population and case-directed systematic review.

Kikuchi-Fujimoto's disease (KFD) and adult-onset Still's disease (AOSD) are rare idiopathic inflammatory conditions of unknown etiology. Ten prior instances of KFD and AOSD occurring together have been reported in the medical literature. These overlaps, together with certain distinguishing clinical and laboratory characteristics in these co-occurrences, offer insight into the pathophysiology of both of these rare disorders. Too, examination of these cases may help improve the diagnostic evaluation and care of patients afflicted with these rare diseases. We therefore report an additional patient with KFD and AOSD occurring in a middle-aged Hispanic female patient and perform a systematic literature review using the PubMed/MEDLINE and Embase databases to further analyze and compare prior identified cases. Our observations in our index case complement and expand previous reports, including new demographic and diagnostic features not seen in prior cases of overlap. Indeed ours is the first in a patient of Hispanic ethnicity, with retroperitoneal lymphadenopathy, as well as with a skin biopsy consistent with AOSD. Each of the reviewed cases of co-occurrence met the diagnostic criteria for both KFD and AOSD. This finding, in the setting of unique clinical and diagnostic manifestations that are not typically seen in either disease entity alone, suggests the presence of an overlap syndrome. Also, many of the shared clinical features and symptomatic responses to targeted therapies implies a similar, yet still poorly understood, pathophysiologic pathway for the two diseases.