#00060970

A 20-year-old man presented with a 3-week history of fevers, night sweats, weight loss, and increasing cervical adenopathy. A comprehensive infectious disease workup was negative. Complete blood count demonstrated a white blood cell count of 2.1 × 10 9/L with 48% neutrophils, 39% lymphocytes, 8% monocytes, 4% eosinophils, and a platelet count of 87 × 10 9/L. Bone marrow studies revealed normocellular marrow with adequate trilineage hematopoiesis. Fludeoxyglucose positron emission tomography/computed tomography exhibited enlarged nonspecific hypermetabolic left cervical nodes with a maximum standardized uptake value of 5.4 (panel A, arrow) and 1.8 cm diameter. An excisional biopsy of the cervical lymph node demonstrated reactive lymphoid follicles with expanded paracortex and extensive paracortical karyorrhexis and necrosis (panels B-C; original magnification ×100 [B]; original magnification ×1000 [C], hematoxylin-eosin stain). Immunohistochemical studies for TCL1 were positive in cells at the interface between necrosis and viable cells (panel D; original magnification ×400). CD123 showed clusters of plasmacytoid dendritic cells at the periphery of the necrosis (panel E; original magnification ×400). A diagnosis of Kikuchi-Fujimoto disease was rendered. Lymph nodes involuted spontaneously on 6-month follow-up without therapy.Kikuchi-Fujimoto disease is an inflammatory self-limited disorder of unknown etiology, characterized by systemic symptoms commonly associated with leukopenia. Karyorrhexis and proliferation of plasmacytoid dendritic cells identified with immunohistochemistry for CD123 and TCL1 (nuclear reactivity) are the pathognomonic morphological findings of the disease. Treatment is mainly supportive, and resolution occurs within 6 months.