Fever of Unknown Origin and Mesenteric Lymphadenitis in a Child: A Diagnostic Challenge Between Tuberculosis, Lymphoma, and Kikuchi-Fujimoto Disease

To the Editors Kikuchi-Fujimoto disease is defined as a rare, benign, self-limiting condition characterized by fever and subacute necrotizing lymphadenopathy, the etiology of which is not yet clearly understood. It was first described in Japan in 1972.1 Although there are hypotheses that autoimmune processes and infections may be the causes, the leading cause of the disease remains unknown. It is usually seen in young adults; however, pediatric cases have also been reported in the literature. A definitive diagnosis is made by demonstrating histiocytic necrotizing lymphadenitis related to pathology in the lymph node biopsy.2 We aimed to increase awareness of this condition in patients with prolonged fever and mesenteric lymphadenitis, whom we followed up. A 13-year-old previously healthy female presented with a 2-week history of persistent fever (up to 39 °C) and abdominal pain. She reported mild diarrhea in the initial days but had no history of dietary indiscretion, chronic illness, or relevant family history. Physical examination revealed no palpable lymphadenopathy or organomegaly. Laboratory investigations showed leukopenia (2870/mm³), mild anemia (hemoglobin: 10.6 g/dL), and elevated inflammatory markers (erythrocyte sedimantion rate: 50 mm/h; C-reactive protein: 11.4 mg/L). Other hematologic and biochemical parameters, including coagulation and autoimmune screening, were within normal limits. Peripheral smear showed no atypical cells. Abdominal ultrasonography identified a cluster of hypoechoic mesenteric lymph nodes in the right lower quadrant, the largest measuring 23 × 19 mm (Fig. 1A,B). Abdominal computerized tomography confirmed mildly reactive lymphadenopathy with no additional pathological findings. Extensive microbiologic workup, including viral and bacterial serologies, was negative. Bone marrow aspiration ruled out hematologic malignancies.FIGURE 1.: A: Mesenteric vascular structures (thick arrow) running between the pathological lymph nodes described between the mesenteric leaves and the hilar vascular structure of the lymph node (open arrow). B: Pathological-looking lymph nodes (asterixes) that have lost their fatty hilum and have significant cortical thickening within the area marked with yellow cursors between the mesenteric leaves in the right lower quadrant, and increased echogenicity in the surrounding fatty tissue in favor of inflammation (white arrow).Due to persistent fever despite empirical antibiotics, an excisional biopsy of the mesenteric lymph node was performed. Histopathologic analysis revealed irregular areas of necrosis surrounded by histiocytic infiltrates, nuclear debris, and absence of neutrophils or viral cytopathic effects—findings consistent with Kikuchi-Fujimoto disease. Viral and autoimmune markers remained negative. High-dose corticosteroid therapy was initiated, resulting in the rapid resolution of fever. The patient remained asymptomatic during follow-up and continues to be monitored for potential development of autoimmune conditions. Kikuchi-Fujimoto disease is a relatively rare and benign condition in the pediatric population, and the exact etiology remains unclear. In most cases reported in the literature, cervical lymphadenopathy and fever are observed, while additional nonspecific findings, such as arthralgia and rash, may also accompany these conditions.3 In our case, it is striking that there is abdominal pain and accompanying mesenteric lymphadenitis with fever. It typically lasts for a few months and rarely recurs. The disease usually responds rapidly to steroids.4 When the literature is reviewed, 114 patients diagnosed with Kikuchi were evaluated in the study conducted by Choi et al.5 It was reported that the patients often presented with prolonged high fever and cervical lymphadenopathy.5 In this case, we aimed to emphasize that Kikuchi-Fujimoto disease can present with symptoms other than cervical lymphadenopathy and that it is a condition that should be considered in the etiology of fever of unknown origin in children. Acknowledgments We thank all the healthcare professionals involved in the diagnosis and treatment of this patient.