Kikuchi-Fujimoto disease: an unusual case report of lymphadenopathy with the absence of classic symptoms.

Introduction and importance: Kikuchi-Fujimoto disease (KFD) is a rare, self-limiting disorder in young adults, characterized by fever and cervical lymphadenopathy. Its uncertain etiology is associated with viral infections and autoimmune conditions, complicating diagnosis. Our patient had no significant past medical conditions, no history of known infections, prescription drug use, or autoimmune diseases within the family, reducing the likelihood of identifiable predisposing factors for KFD. Case presentation: We report a 20-year-old Asian male with a 2 × 3 cm non-tender, matted swelling in the posterior cervical triangle, without systemic symptoms. Despite six months of anti-tubercular treatment for presumed tuberculous lymphadenitis, there was no improvement. The diagnostic workup included tests for autoimmune markers (ANA, ENA panel) and viral markers (CMV, EBV), all of which were negative, as well as imaging studies, including chest x-ray and echocardiography, were normal. Ultrasound revealed multiple enlarged cervical lymph nodes. Excisional biopsy confirmed the diagnosis. Clinical discussion: This case highlights the challenges in diagnosing KFD, especially when classic symptoms are absent. The initial misdiagnosis of tuberculous lymphadenitis led to prolonged treatment, despite negative viral and autoimmune markers. Histopathological examination played a critical role in identifying the hallmark of KFD, including necrotizing lymphadenitis with abundant histiocytic infiltration, karyorrhectic debris, and absence of neutrophils, differentiating it from cancer and lupus lymphadenitis. The patient responded well to corticosteroid therapy, achieving full resolution. Conclusion: This case highlights the importance of considering KFD in persistent cervical lymphadenopathy. While the prognosis is favorable, further research is needed to clarify its pathogenesis and improve diagnostics.