(451) A Rare and Life-Threatening Presentation of Ehrlichia-Induced Hemophagocytic Lymphohistiocytosis

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a rare and life-threatening syndrome of excessive and ineffective immune activation. It is precipitated by immunosuppression, infection, malignancy or rheumatological disorders (Patel et al., 2020). Due to its varying clinical presentations, diagnosis and treatment of HLH can be delayed, which results in a high mortality rate (Singh et al, 2022). We report a case of Ehrlichia-induced HLH in an immunocompromised patient.

Description: A 55-year-old man with hypertension, diabetes, and rheumatoid arthritis on infliximab presented with fever, weakness, confusion, and oliguria. Laboratory evaluation showed platelets 22,000/µL, WBC 1,000/µL, hemoglobin 12.2g/dL, creatinine 5.9mg/dL, BUN 86mg/dL, AST/ALT 216/139 U/L, and total bilirubin 1.8mg/dL. On CT abdomen, liver and spleen were normal size. He further declined requiring vasopressor and ventilatory support. Further workup revealed triglycerides 297mg/dL, ferritin 28,442ng/mL, LDH 960U/L, soluble IL-2R 5,204U/mL, CXCL9 141,576pg/mL, and 12% NK cell activity. His bone marrow biopsy was compatible with HLH, and high dose dexamethasone and rituximab were started. Patient had a history of recent tick exposure and infectious work up revealed concurrent EBV and Ehrlichia infections. Doxycycline was started with drastic clinical improvement. He was weaned off vasopressors, extubated and ultimately discharged to rehab. HLH was thought to be related to Ehrlichiosis considering rapid response to doxycycline.

Discussion: HLH is a rare and aggressive disease of excessive immune activation (Mitma et al, 2021) with poor prognosis if its underlying etiology is not promptly treated (Otrock et al, 2015). Scarce literature is available on the association of Ehrlichia and HLH and to our knowledge there are no cases of EBV and Ehrlichia co-infection reported. Though history of rheumatologic condition and immunosuppression was present in our case, a high level of suspicion of secondary causes of HLH prompted further investigation. Due to prevalence of tickborne diseases in Kentucky, infectious work-up was performed that uncovered his secondary cause of HLH (Pasternak et al, 2023). We recommend a complete history and evaluation for Ehrlichia when indicated in those with HLH, as early intervention may improve outcomes.