UMEM Educational Pearls

Rocky Mountain spotted fever (RMSF)

Systemic small vessel vasculitis caused by R rickettsii which is transmitted by a tick bite.


Clinical features: fever, headache, myalgia, nausea, vomiting, and characteristic rash. Rash usually appears before the sixth day of the illness initially on the wrists and ankles, and spreads to the trunk within hours.  Initially. It is erythematous and macular, later becoming petechial.

Laboratory findings: thrombocytopenia, anemia, and hyponatremia.

Complications: meningitis, multiorgan involvement, DIC, shock, and death. 

Treatment: doxcycycline (even despite the risk of dental staining in children younger than 8 years old)


American Academy of Pediatrics. Rickettsial diseases, Rickettsialpox, Rocky Mountain spotted fever. In: Pickering LK, ed. Red Book: 2006 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, Ill: American Academy of Pediatrics; 2006:529-534.