LCDR Naval Medical Center Portsmouth, United States
Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a state of pathologic immune hypersensitivity caused by numerous inflammatory triggers. Presented is a case of murine typhus infection leading to secondary HLH and multiorgan failure.
Description: A 59-year-old male with heart failure with reduced ejection fraction presented to the emergency department after a motor vehicle collision. He was recently admitted at a local hospital for sepsis and left against medical advice. On trauma survey, his only injury was a left great toe abrasion; however, he became profoundly encephalopathic and hemodynamically unstable. He was admitted to the ICU for acute hypoxic respiratory failure, undifferentiated shock, and acute kidney injury. He was started on vancomycin, piperacillin-tazobactam, norepinephrine and dobutamine for mixed distributive/cardiogenic shock. The patient’s condition continued to decline, requiring additional vasopressors and continuous renal replacement therapy (CRRT). Closer evaluation of laboratory trends revealed leukopenia, thrombocytopenia, and elevated liver enzymes. Further history indicated the patient was construction worker in Chesapeake, Virginia. Doxycycline was started for potential arthropod- versus tick-borne infection. Ferritin levels returned at >67,000 ng/mL and IL-2 at >7900 U/mL, concerning for secondary HLH. Dexamethasone 40mg daily for four days was also added. Within 48 hours, the patient was weaned off vasoactive medications, extubated, and transitioned from CRRT to intermittent hemodialysis. Rickettsia typhi titers returned elevated at 1:256, consistent with a diagnosis of murine typhus.
Discussion: HLH is mediated by pathologic immune hyperactivity, leading to overactivation of macrophages, hemophagocytosis, and excessive cytokine production. In this case, HLH was precipitated by murine typhus infection. Murine typhus, caused by Rickettsia typhi, is spread via infected fleas. While most patients experience a mild influenza-like illness, some develop severe illness. Notably, there is a nexus of murine typhus near Chesapeake, Virginia. Doxycycline is first line therapy. When patients are not responding standard therapies, it is important to consider atypical infections and their effects on the immune response.
