Rocky mountain spotted fever.

Rocky mountain spotted fever (RMSF) is a fulminant tick-borne infection by Rickettsia rickettsii. The classical diagnostic triad is fever, headache and rash in a patient with a recent tick bite. With prompt, appropriate antimicrobial therapy, patient outcomes are excellent. However, RMSF is often misdiagnosed, particularly during the initial stages of illness, and as a result, patient outcomes are sometimes suboptimal.