An Unusual Cause of Lymphadenopathy: Kikuchi–Fujimoto Disease Associated with Systemic Lupus Erythematosus

Abstract Kikuchi–Fujimoto disease (KFD), or histiocytic necrotizing lymphadenitis, is an uncommon inflammatory disorder predominantly affecting young women, often mimicking lymphoma or infectious lymphadenitis. Its coexistence with systemic lupus erythematosus (SLE) is rare and diagnostically complex due to overlapping clinical and serological features. We report the case of a 29-year-old female presenting with a 5-week history of bilateral cervical lymphadenopathy, low-grade fever, alopecia, and constitutional symptoms. Laboratory findings revealed mild anemia, leukopenia, elevated erythrocyte sedimentation rate, and positive antinuclear antibody and anti-double-stranded DNA antibodies with a homogeneous pattern at 1:160 titer, yielding an european alliance of associations for rheumatology / american college of rheumatology (EULAR/ACR) 2019 SLE score of 13. Lymph node excision biopsy demonstrated necrotizing lymphadenitis with abundant karyorrhectic debris and CD68+ histiocytic infiltrate. Fluorine-18 fluorodeoxyglucose positron emission tomography–computed tomography revealed hypermetabolic lymphadenopathy in cervical, supraclavicular, axillary, and iliac regions. The patient showed rapid clinical improvement with corticosteroids and hydroxychloroquine. This case underscores the importance of histopathological evaluation in distinguishing KFD from lymphoma and recognizing SLE overlap.