C50-05 Kikuchi-Fujimoto Disease and Hemophagocytic Lymphohistiocytosis in an African-American Adult: A Rare Overlap

Introduction Kikuchi-Fujimoto disease (KFD) is a rare, self-limited cause of necrotizing lymphadenopathy and fever, most often reported in Asian populations. KFD is rarely associated with hemophagocytic lymphohistiocytosis (HLH), a life-threatening hyperinflammatory syndrome caused by uncontrolled immune cell activation and excessive cytokine release. The overlap of these conditions has been described sparsely in the literature, mostly in pediatric populations. This case highlights the clinical course of an African-American adult female who presented with sepsis and was ultimately diagnosed with KFD and HLH. Case A 38-year-old African-American female with diabetes, hypertension, and recent robotic hysterectomy and salpingectomy for fibroids presented with five days of fevers, chills, and diffuse pain. She had recently completed a two-week IV piperacillin-tazobactam course and nephrostomy exchange for presumed pyelonephritis after a complicated postoperative course, including surgical abscess and ureteral injury requiring nephrostomy tube placement. On admission, she was tachycardic, febrile, and hypertensive. Exam revealed right flank tenderness and intact drains. Laboratory evaluation showed leukopenia, anemia, and normal creatinine and urinalysis. She was started on piperacillin-tazobactam and vancomycin. Hematology was consulted for severe neutropenia and filgrastim was administered. Extensive imaging and lumbar puncture revealed no infectious source. Despite broadening to meropenem, she remained febrile with worsening headaches, ear pain, and rigors. Ferritin was markedly elevated (43,408), raising concern for HLH. Repeat labs showed transaminitis, ferritin >100,000, cytopenias, hypofibrinogenemia, coagulopathy, and inflammatory markers consistent with HLH (HScore 269, 99% probability). Hematology, rheumatology, and the HLH task force were consulted. An exam later revealed tender cervical lymphadenopathy. CT imaging revealed necrotic right cervical nodes; biopsy confirmed necrotizing lymphadenitis consistent with Kikuchi disease. Given persistent fevers, she received IV methylprednisolone for three days followed by an oral prednisone taper. Following clinically improved and was discharged on an oral prednisone taper. Significance This case underscores the risk of anchoring bias and the importance of re-evaluating differentials when patients fail to improve. Sepsis requires rapid recognition and early treatment to reduce morbidity and mortality. Similarly, HLH requires a high index of suspicion, as it often mimics sepsis. Ferritin, inflammatory markers, and the HScore help discriminate HLH from sepsis. While Kikuchi disease is most often reported in Asian and pediatric populations, this case introduces a rare overlap of Kikuchi-HLH in a young African-American woman. Recognizing the possibility of Kikuchi-HLH in adults, irrespective of race, expands clinical knowledge and may prevent delays in diagnosis and care, as HLH carries a mortality rate of 40-50%.