Review Question - QID 106904

This patient with fever, headache and a maculopapular rash on the extremities after outdoor activity likely has Rocky Mountain Spotted Fever (RMSF). For patients with suspected Rocky Mountain Spotted Fever, the most appropriate next step in management is administration of doxycycline.

RMSF is a tick-borne infection caused by Ricketsia rickettsii. Incidence is highest in the southeastern and south-central United States (e.g Tennessee, North Carolina). It often presents with fevers, headaches, myalgia, and malaise, starting less than one week after exposure. The associated, "spotted" rash starts as a maculopapular rash on the ankles and wrist, and eventually develops into a petechial rash that moves to the trunk. It appears within 2-6 days of exposure due to a small vessel vasculitic process, although some patients with RMSF will not have the classical rash. RMSF is the most commonly reported Rickettsiel infection in the United States, and delayed diagnosis can result in death. Doxycycline is the therapy of choice for patients with suspected RMSF, and should be started promptly prior to confirmatory testing. Despite the theoretical risk of tooth-staining, doxycycline remains the agent of choice for suspected RMSF in children.

Gayle and Ringdahl review the symptoms and treatments of tick-borne illnesses. They note that Lyme disease is the most common tick-borne illness, but new interest in tularemia has resulted from concern for its use as a weapon in biological warfare. They emphasize that RMSF can be deadly within 8-15 days if not treated, and that serious sequela of infection include encephalitis, non-cardiogenic pulmonary edema, ARDS, and arrythmias.

Mosites et. al performed a survey of health care professionals in Tenessee to determine which health care professionals were most lacking in training on RMSF. They noted that physicians who had been practicing for more than 20 years were more likely to have a solid understanding of the disease. In addition, a high proportion of participants did not know that doxycycline is still the drug of choice in patients <8 years old (in comparison to Lyme disease, which is treated with amoxicillin in young patients).

Figure A shows a rash consistent with Rocky Mountain Spotted Fever. This rash is present in up to 90% of patients with RMSF. Classically, the rash begins around the palms, soles, wrist, and ankles before spreading inward to the extremities and trunk.

Incorrect Answers:
Answer 1: Amoxicillin is an appropriate alternative agent for treatment of suspected Lyme disease in children under the age of 8. While patients often display similar non-specific flu-like symptoms, the pathognomonic erythema migrans rash would be expected.

Answer 2: Azithromycin would be appropriate for treatment of suspected atypical pneumonia due to infection with Chlamydia or Mycoplasma species, which may also present with a diffuse rash. However, cough would be expected. Fever and headache, along with this patient's history make RMSF more likely.

Answer 3: Ceftriaxone is indicated for some late complication of disseminated Lyme disease such as Lyme carditis. However, these often present several weeks to months after exposure. Fever and headache, along with this patient's history make RMSF more likely.

Answer 5: Vancomycin, ceftriaxone, and dexamethasone would be appropriate for coverage of suspected bacterial meningitis. However, signs of meningeal irritation would likely be present. This patient's fever, headache, rash, and history of recent outdoor activity make RMSF more likely.

Bullet Summary:
For patients with suspected Rocky Mountain Spotted Fever, the most appropriate next step in management is administration of doxycycline.