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Research Snapshot Theater: Immunology, Adult

Delayed Diagnosis of RMSF-Induced HLH in an Elderly Female With Nonspecific Symptoms

Monday, March 23, 2026
2:30 PM - 3:30 PM Central Time
Location: Connections Central - RST 09

  • Joseph O. Odeyemi, MD

    University of Kansas Medical Center, Kansas

    Disclosure(s): No relevant financial relationship(s) to disclose.

  • DM

    David Maundu, MD

    Resident Physician
    University of Kansas - Wichita

    Disclosure information not submitted.

  • RS

    Raj Shah, MD

    Resident Physician
    University of Kansas - Wichita

    Disclosure information not submitted.

  • JE

    Jessica Emoto, MD

    Resident Physician
    University of Kansas - Wichita

    Disclosure information not submitted.

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory syndrome often triggered by infections, most commonly viral. Bacterial causes like Rocky Mountain Spotted Fever (RMSF), caused by Rickettsia rickettsii, are less common. RMSF-associated HLH is rarely reported and poses significant diagnostic and therapeutic challenges. We present a fatal case of HLH triggered by RMSF in an elderly woman, underscoring the importance of early recognition and treatment.


Description: A 79-year-old woman from Kansas presented with two weeks of weakness, headache, and intermittent fevers. She had visited the emergency room multiple times. Labs revealed hyponatremia, leukopenia, thrombocytopenia, and mild renal impairment. She was treated symptomatically each time and discharged home.
Her symptoms worsened, and she was admitted with worsening cytopenia, rising creatinine (4.06 mg/dL), and metabolic acidosis. On arrival, she met sepsis criteria and labs revealed pancytopenia, elevated troponin, hyperferritinemia (>40,000 ng/mL), hypertriglyceridemia (261 mg/dL), hypofibrinogenemia (97 mg/dL), and mild transaminitis.
She was empirically started on broad-spectrum antibiotics including doxycycline. A bone marrow biopsy showed hemophagocytosis, and serology confirmed Rickettsia rickettsii, establishing the diagnosis of RMSF-induced HLH. She was started on dexamethasone and etoposide per HLH-2004 protocol.
Despite treatment, her condition declined with worsening encephalopathy, persistent renal failure requiring dialysis, and vasopressor dependence. After a family meeting, she was transitioned to comfort-focused care on hospital day nine.


Discussion: This case describes a rare complication of RMSF in an elderly patient. RMSF may present atypically in older adults, increasing the risk of delayed recognition and poor outcomes. Shared features of HLH and RMSF such as fever, cytopenia, and organ dysfunction can obscure diagnosis. Our patient met HLH-2004 criteria and had a high HScore, supporting the diagnosis.
Despite receiving doxycycline, dexamethasone, and etoposide per treatment protocols, she developed progressive multi-organ failure. This case highlights the need for early recognition and timely treatment in patients with severe systemic illness from RMSF and suspected HLH.