FEVER OF UNKNOWN ORIGIN: ATYPICAL CLINICAL PRESENTATION OF MURINE TYPHUS

ABSTRACT

CASE 66yo woman with a past medical history of hypertension and monoclonal gammopathy of undetermined significance was sent from clinic in winter for 4 days of worsening fevers and sinus congestion unrelieved by over-the- counter medications. COVID and flu negative. Patient has had no sick contacts or recent travel and has pet cats but no recent scratches. Initial chest x-ray showed no acute processes, but patient was continuing to have fevers up to 103 with mild dyspnea and chills so a CT chest was completed which showed ground glass opacities in the right middle lobe. Blood and sputum cultures were obtained, and patient was started on ceftriaxone and azithromycin for community acquired pneumonia. Urine strep and legionella antigens were also acquired, both negative. Over the next two days, she continued to have high fevers and chills at nights with leukocytosis, thrombocytopenia, hyponatremia, and notable worsening of mild elevation of liver enzymes on admission. Cultures were negative and patient had no other indication of an infection aside from the cyclical fevers therefore empiric doxycycline was added for coverage of atypical infections. Over the next two days, she continued to have nightly fevers up to 103 so ID was consulted for fever of unknown origin. On repeat exposure assessment, patient revealed that she lived with multiple animals including cats, dogs, parakeets, chickens, geese and a pony. Patient was continued on doxycycline while additional lab tests were sent for atypical infections including Rickettsia typhi, Coxiella brunetti (Q fever), and Brucella spp given patient's history of exposure to multiple animals at home. Patient was discharged on doxycycline after being afebrile for 48hrs with declining white count and liver enzymes. Lab results confirmed the diagnosis with high titers for Rickettsia typhi IgG and IgM. IMPACT/DISCUSSION: This case illustrates an atypical presentation of murine typhus with pneumonia in winter. There are several key teaching points in this case 1. Ricketssia typhi infections have largely nonspecific symptoms therefore it should should be included in differential diagnoses of febrile illnesses with thrombocytopenia and elevated liver enzymes 2. Although a complete history is acquired on admission, it is important to revisit and review information again when a clinical diagnosis has not been established 3. Defeverscence after starting doxycycline can take anywhere from 4 to 66hrs so fevers during this timeframe is not an indication of failure of therapy CONCLUSION: Murine typhus presents with non-specific symptoms so it should be included in the differential diagnosis of patients with fevers of unknown origin with potential exposure to flea-bearing animals. The optimal therapy is doxycycline 100mg twice a day for seven days. Patients should also be advised to treat their animals for fleas to prevent recurrent infections.