[Kikuchi-Fujimoto Disease Developing after Brucellosis and Leptospirosis Coinfection Presenting with Gastrointestinal System Bleeding: A Case Report].

Brucellosis and leptospirosis are zoonotic infections with overlapping clinical features, especially in endemic regions. Coinfection of these pathogens is rare and may trigger secondary inflammatory disorders through excessive immune activation. In this report, a rare case of Kikuchi-Fujimoto disease following brucellosis and leptospirosis coinfection with gastrointestinal bleeding was presented. A 31-year-old male presented with fever, malaise, diarrhea and black, foul-smelling stools for three days. Physical examination revealed conjunctival hyperemia, hepatosplenomegaly and diffuse abdominal tenderness. Laboratory findings showed elevated AST, ALT and creatine kinase levels, thrombocytopenia, and prolonged international normalized ratio. Upper gastrointestinal endoscopy demonstrated antral erosions with an active bleeding site. Serologic tests revealed positive Brucella agglutination and Leptospira microscopic agglutination tests with titers of 1/320 and 1/400, respectively. The patient was treated with doxycycline and rifampicin. Three weeks later, he developed painful cervical lymphadenopathy. Excisional biopsy showed necrotizing lymphadenitis consistent with Kikuchi-Fujimoto disease. The patient improved with symptomatic therapy and showed no recurrence at three-month follow-up. Although brucellosis and leptospirosis coinfection is rare, it may induce immune dysregulation leading to secondary inflammatory lymphadenitis. This case highlights the potential link between zoonotic coinfections and Kikuchi-Fujimoto disease and underlines the importance of considering this diagnosis in patients presenting with fever and lymphadenopathy following infectious episodes.