A 27-year-old woman was admitted to a hospital due to intermittent fever for 20+ days and swelling pain in knee joint for 7 days.Patients was with persistent fever,the highest temperature to 40.1°C,the double knee joint swelling pain,a large number of scattered red needle-like rash were visible on bilateral hands and legs,lymph-adenectasis,splenectasis,bilateral hands interphalangeal joint and knee joint swelling pain,lymph nodes were con-fined to the bilateral axillary with soft texture,local tenderness,and good activity.Pathological results of left axil-lary lymph node showed the following finding:fragmental lymph node tissue with incomplete structure,lymphoid follicles existed,there were diffuse histocytes,immunoblasts,and a few small lymphocytes proliferation in the re-duced or disappeared area of follicular,caryokinesis could be easily seen,there were patches of necrosis foci with varied size,nucleus disintegrated,fibrinoid necrosis blood vessel with bleeding could be seen.Immunohistochemical detection showed the following results:CD3 (diffuse +);CD20 (follicular +);CD79α(follicular +);CD68 (+);EMA (-);ALK (-);CD15 (a small amount of cells +);CD30 (+),CD4 (-),CD5 (+);CD10 (-);bcl-2 (+);CD21 (+);telomerase B (-);TIA-1 (-);EBV(-)Ki-67 (+).Through a combination of clinical and immunohistochemical detection results,the diagnosis of histiocytic necrotizing lymphadenitis was made.Patient discontinued antimicrobial drugs,after she was treated with 5% glucose 100 mL + hydrocortisone sodium succinate 200 mg intravenous drip for 3 days,patients had no fever,axillary lymph node gradually dwindled.Then patients was treated with methylprednisolone 8 mg/d,twice a day,reduced 1 tablet every two weeks,and stopped eventual-ly.Patients was followed up for two years,repeated examination of blood routine,liver and kidney function were in the normal range,bilateral knee didn’t swell,could walk freely,there appeared no enlargement of lymph node.