Abstract: Objective To study the diagnosis and treatment of histiocytic necrotizing lymphadenitis(HNL) accompanying Hashimoto's thyroiditis(HT) and autoimmune hemolytic anemia(AIHA) by reporting a case of unknown origin fever and reviewing its related literature. Methods The clinical data about a patient with HNL accompanying HT and AIHA admitted to the Department of Fever-Related Diseases in our hospital as a case of unknown origin fever were retrospectively analyzed with its related literature reviewed. Results The patient was a 56-year-old female manifested as unknown origin fever accompanying arthralgia, myalgia, sore-throat, transient skin rash, thyroid enlargement, axillary and inguinal lymph node enlargement, anemia, and was diagnosed as HNL accompanying HT and AIHA according to its clinical manifestations, pathological examination and bone marrow biopsy. Conclusion HNL accompanying HT and AIHA is rarely encountered in clinical practice. HNL and autoimmune diseases should be considered in patients with fever of unknown origin. Its diagnosis depends mainly on its pathological examination and its treatment depends mainly on glucocorticoid.