Case report: hemophagocytic lymphohistiocytosis secondary to bartonella henselae bacteremia in a renal transplant recipient

Abstract Background Bartonella henselae can cause disseminated infection in renal transplant recipients, however, cases presenting with hemophagocytic lymphohistiocytosis (HLH) triggered by bacteremia are extremely rare. Case presentation A 33-year-old female patient, three years after renal transplantation, presented with headache and fever, which failed to resolve with empirical carbapenem therapy. Laboratory tests revealed pancytopenia, significantly elevated ferritin and soluble IL-2 receptor, and bone marrow biopsy showed hemophagocytosis, confirming the diagnosis of hemophagocytic lymphohistiocytosis (HLH). Routine pathogen screening yielded no causative organism, but metagenomic next-generation sequencing (mNGS) of peripheral blood detected Bartonella henselae as the most probable causative pathogen. Upon further inquiry, the patient recalled being scratched by a kitten approximately one month prior to symptom onset. Treatment involved discontinuation of oral immunosuppressants, followed by short-course antimicrobial therapy with doxycycline and rifampin guided by repeated mNGS monitoring. Concurrently, HLH was managed with dexamethasone and intravenous immunoglobulin. The patient’s symptoms rapidly improved, and her blood counts gradually recovered. At 6-month follow-up, there was no recurrence of disease, and renal allograft function remained stable. Summary Bartonella henselae should be considered a rare and probable infectious trigger of secondary HLH following renal transplantation, warranting heightened clinical vigilance. For patients with bacteremia as the primary clinical manifestation and no disseminated multi-organ lesions, short-course individualized anti-infective therapy can be conducted under the guidance of dynamic mNGS.