P2.L236: Myositis and Encephalopathy as Presenting Symptoms in Murine Typhus

Introduction: Murine typhus cases in children have increased substantially in recent years, especially in southern Texas, California, and Hawaii. The most common clinical presentation of murine typhus includes fever, rash, and headache. A predominant presentation with myositis and/or encephalopathy is rare.

Case Description: A four-year-old unvaccinated but previously healthy male presented with 3 days of fever, altered mental status, and inability to bear weight on the right side. One week prior, he had runny nose, watery eyes and a non-itchy full body rash after visiting a family member with cats and dogs. He then developed fever, back pain, right hip pain, and broad-based gait that progressed to inability to bear weight.
Upon arrival, the patient was dazed and mumbling, hypothermic, and admitted to the pediatric intensive care unit briefly before altered mental status resolved. He received fluid resuscitation, a dose of dexamethasone, and started on IV ceftriaxone and vancomycin. On physical examination he had right hip tenderness, and restriction of movement with right hip flexion and knee extension. Laboratory results are shown in Table 1. CT brain and chest radiograph were unremarkable.
The patient was febrile the first 5 days of admission. Blood, CSF and urine cultures had no growth. Infectious disease was consulted, and doxycycline was added due to concern for rickettsial diseases. Antibody titers for Epstein Barr virus, Cytomegalovirus, and measles, mumps, and rubella were all negative. MRI hip/pelvis and spine revealed diffuse myositis.
Within 24 hours of starting doxycycline, fevers down trended and right hip pain improved. The Rickettsia typhi IgG titer was positive at 1:64, while the IgM titer was 1:1024. He completed a 10-day course of doxycycline with resolution of symptoms.

Discussion: This report showcases pediatric murine typhus with myositis and encephalopathy as a predominant manifestation, rarely represented in the current literature. Murine typhus is caused by the Rickettsia typhi, commonly transmitted by fleas. We reviewed 16 pediatric patients admitted to the inpatient unit from 2018 to 2023 with murine typhus (Table 2). Among them, 4 presented with significant localized myositis. Three of these four patients also had fever, rash and myalgias. Of all 16 patients, 75% reported animal exposure. Table 2 provides an overview of pediatric murine typhus cases reported in the literature and presenting symptoms.
Diagnostic testing for murine typhus is done via indirect immunofluorescence antibody (IFA) assay, ideally confirmed by a >4-fold increase in titers between acute and convalescent sera. Murine typhus infection can self-resolve, but doxycycline is the treatment of choice, with evidence of shortening fever course and hospitalization.

Conclusion: It is important to recognize unusual clinical manifestations of murine typhus in children for early diagnosis and treatment. Prompt antibody titer testing and initiation of doxycycline is necessary for faster recovery and prevention of complications.