Rocky Mountain Spotted Fever (RMSF) is a tick-borne illness caused primarily by Rickettsia rickettsii. It can be found in all 48 contiguous U.S. states. The incidence of RMSF in the U.S. is rising, with 495 cases in year 2000 to over 4,000 in 2016.
Of note, while children represent less than 10% of all cases, they comprise approximately 22% of all fatalities. Compared with adults, children <10 years of age are 5 times more likely to die from RMSF.
Illness begins with non-specific symptoms including fever, headache, nausea, vomiting, and myalgias 3-12 days following a bite with a carrier tick. While 90% of patients have a rash during the course of their illness, the rash is often non-specific within the first few days. Development of petechiae is an ominous finding, reflective of a progressive vasculitis. Symptoms may progress to multi-organ system failure, coma, and death if untreated.
Common laboratory findings include hyponatremia, thrombocytopenia, and elevated liver enzymes. Diagnosis is confirmed with serology testing. Due to its high morbidity and mortality in children, the preferred treatment for RMSF is doxycycline regardless of age.
Take Home Points
- Due to the high morbidity and mortality of RMSF (especially in children), treatment should be initiated on history and clinical findings and not delayed for serologic testing confirmation.
- Doxycycline is the preferred treatment for suspected cases of RMSF in all ages.