ricketsia

Rocky Mountain spotted fever (RMSF) is a tick-borne illness caused by Rickettsia rickettsii. The classic triad of symptoms includes fever, headache, and rash. Early nonspecific manifestations (eg, fever, nausea, myalgias, arthralgias) are followed by the development of erythematous macules on the wrists and ankles around days 3-5 of illness. Rash may spread to the trunk, palms, and soles, and macules often evolve into petechiae. Although initial leukocyte count is typically normal, thrombocytopenia, hyponatremia, and transaminitis are characteristic.

RMSF is diagnosed presumptively based on clinical findings as serologic testing is generally negative in early disease. Empiric antibiotics are initiated as soon as possible without waiting for confirmatory test results, as a delay in treatment can lead to serious complications (eg, encephalitis, pulmonary edema, arrhythmia) and increased mortality. Doxycycline is the recommended antibiotic for all patients, including children and pregnant women. The risk of teeth discoloration is minimal with a short treatment course; no other medications are as safe and effective.