Kikuchi-Fujimoto Disease: A Rare Cause of Fever and Generalized Lymphadenopathy.

Kikuchi-Fujimoto disease (KFD), recognized as histiocytic necrotizing lymphadenitis, is an uncommon, non-threatening, and self-resolving condition mainly seen in young adults. It frequently appears with cervical lymphadenopathy and fever, often resembling infectious, autoimmune, or malignant disorders like lymphoma. KFD poses a diagnostic challenge because of its nonspecific clinical and radiological characteristics, potentially resulting in unwarranted tests and intense treatments. We report the case of a 25-year-old male patient who presented with a 12-day history of ongoing high-grade fever, along with vomiting and a dry cough. Preliminary laboratory tests indicated leukopenia and increased inflammatory markers, whereas imaging examinations ruled out acute abdominal issues. Despite broad-spectrum antibiotics, daily fever spikes continued, leading to a comprehensive investigation for pyrexia of unknown origin. Tests for infectious origins, such as tuberculosis, brucellosis, malaria, and viral factors, were negative. Computed tomography of the chest showed mediastinal and hilar lymphadenopathy, while neck ultrasound identified several bilateral cervical lymph nodes, with some exhibiting loss of fatty hilum. Excisional biopsy of cervical lymph nodes revealed geographic necrosis with karyorrhectic debris, paracortical enlargement, and lack of neutrophilic infiltration, indicative of necrotizing histiocytic lymphadenitis. Flow cytometry and immunohistochemistry ruled out cancer, and a diagnosis of KFD was made. The patient showed improvement with supportive care and was released with follow-up appointments in outpatient rheumatology. The follow-up autoimmune evaluation yielded negative results. Thus, KFD should be taken into account in young individuals showing unexplained fever and lymphadenopathy once infectious and malignant reasons have been ruled out. The definitive diagnosis depends on excisional biopsy of lymph nodes and histopathological analysis. Identifying this entity is essential to prevent misdiagnosis, unnecessary treatment, and patient distress. Due to its link to systemic lupus erythematosus, prolonged monitoring is advised. KFD is a significant differential diagnosis for pyrexia of unknown origin accompanied by lymphadenopathy. Timely histopathological verification guarantees suitable treatment and avoids unnecessary procedures.