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Rocky Mountain Spotted Fever USMLE Notes & Mnemonics contains all the high-yield points you need to know.

  • Rocky Mountain Spotted Fever: A severe tick-borne illness caused by Rickettsia rickettsii.


  • Common in the southeastern and south-central United States.
  • Peak incidence in spring and early summer.


  • Transmitted by the bite of infected ticks (Dermacentor species). (Ref)


  • Rickettsia rickettsii infects endothelial cellsvasculitis.

Clinical Features:

  • Incubation Period: 2-14 days post-tick bite.
  • Early Symptoms: Fever, headache, malaise, myalgia.
  • Rash: 2-5 days after fever onset; starts on wrists, ankles, then spreads to palms, soles, and trunk.
  • Severe Cases: Can involve CNS, respiratory, gastrointestinal, and renal systems.


  • Clinical Diagnosis: Based on symptoms, history of tick exposure, and characteristic rash.
  • Serology: Indirect immunofluorescence assay (IFA) is the gold standard.
  • PCR: For Rickettsia rickettsii DNA detection.


  • Doxycycline: First-line treatment for all ages, including children.
  • Start Treatment Immediately: If RMSF is suspected, without waiting for confirmation.


  • Severe Cases: Can lead to hospitalization, long-term health problems, or death.
  • Potential Issues: DIC, multiorgan failure, limb gangrene necessitating amputation.


  • Tick Avoidance: Protective clothing, tick repellents.
  • Prompt Tick Removal: To reduce transmission risk.

Mnemonic: “RMSF – Really Mean Symptoms Fast

  • Rickettsia
  • Mountains (Rocky Mountains, but more common in Southeast US)
  • Spots (rash on wrists, ankles, palms, soles, trunk)
  • Fever, headache, myalgia

Chart: RMSF Key Features and Management

FeatureDescriptionManagement Strategy
RashWrist, ankles → palms, soles, trunkDoxycycline
FeverHigh fever within 2 weeks of tick biteImmediate treatment initiation
HeadacheSevere headache
ComplicationsDIC, multiorgan failureHospitalization, supportive care
PreventionTick avoidance, prompt removal

Note: On the USMLE, RMSF is often tested in the context of a patient with a history of tick exposure presenting with fever, headache, and a characteristic rash. Early recognition and prompt treatment initiation with Doxycycline is crucial, as delayed treatment can lead to severe complications.

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