Kikuchi-Fujimoto disease co-occuring with Hashimoto thyroiditis: A case report and literature review.

We introduce a 16-year-old female who presented with tender cervical lymphadenopathy, prolonged fever, and hypothyroidism. After excluding common causes of fever of unknown origin, a surgical biopsy of cervical lymph nodes revealed Kikuchi-Fujimoto disease. The patient showed improvement with a short-term course of NSAIDs. An increased titre of thyroperoxidase antibody led to a diagnosis of Hashimoto's thyroiditis during stable condition. This report underscores the importance of considering Kikuchi-Fujimoto disease in the differential diagnosis of prolonged fever of unknown origin with lymphadenopathy and highlights the association with Hashimoto's thyroiditis, advocating for vigilance regarding hypothyroidism in long-term follow-up after Kikuchi-Fujimoto disease recovery.