A50-03 Anaplasmosis-induced Hemophagocytic Lymphohistiocytosis: A Sepsis Mimic in Critically Ill Patients

Abstract Rationale Human granulocytic anaplasmosis (HGA), is tick-borne illness endemic to the Northeastern United States. Most infections are self-limiting; however, HGA can trigger severe life threatening complications include Hemophagocytic Lymphohistiocytosis (HLH). HLH is a sepsis-mimic hyper-inflammatory disorder presenting with cytopenia and multi-organ dysfunction. We present three cases of HLH induced by anaplasmosis requiring intensive care management. Methods A retrospective data review was conducted on three critically ill patients admitted to the intensive care unit between 2023 and 2024 with anaplasmosis, with three patients developing progressive organ dysfunction alongside cytopenia despite doxycycline therapy. Laboratory markers including Soluble IL-2 receptors, liver function tests, ferritin and triglycerides were reviewed. HLH was diagnosed using H-Score, and HLH-2004 criteria. Results All three patients presented with fever, fatigue and laboratory evidence of pancytopenia. Despite appropriate anaplasmosis therapy, worsening clinical status and multiorgan dysfunction endured requiring higher level of care. In the three cases, ferritin was noted to be 10,000 ng/ml, and triglycerides were elevated, rendering HLH more likely. H-scores ranged from 186 to 210, while meeting at least 5 out of 8 of the HLH-2004 criteria. Treatment with anakinra, corticosteroids, IVIG lead to rapid clinical improvement with survival of all patients. Conclusions HLH, though rare, markedly increases mortality rates if not diagnosed and treated promptly. Blood smear examination, serology with PCR do provide a great diagnostic tool for anaplasmosis. Failure to improve following initiation of doxycycline should raise the question of a complication induced by anaplasmosis or a concurrent undiagnosed medical condition. Ordering ferritin levels, triglycerides, interleukin-2 receptor levels, and LFTs as well as maintaining a high index of clinical suspicion is important to rule in/out a rare diagnosis, yet life threatening. Key treatment including immunomodulatory therapy with early initiation of IVIG, Anakinra, and corticosteroids. Increasing awareness of Tick-borne induced HLH among critical care physicians may facilitate a timelier recognition and treatment. This abstract is funded by: None