Rocky Mountain Spotted Fever – CME from Pediatric EM Morsels

Rocky Mountain Spotted Fever CME available.

Just go to the link above–everything in the post is relevant.


Ticks are disgusting (no offense ticks). They engorge themselves on our blood, becoming bloated sloth-like sacs of our serum. While that is certainly not appealing, what makes them most offensive is their tendency to transmit awful diseases to us.  These diseases (and unique conditions – Tick Paralysis*) are numerous, but one of the most important to review (especially for those of us in North Carolina, USA) is Rocky Mountain Spotted Fever.

*Be sure and review Dr. Fox’s post Tick Paralysis. It is very helpful for ascending paralysis.

So go review the entire  Rocky Mountain Spotted Fever post now.

Still here are some excerpts:

RMSF Presentation

  • Initial symptoms are typically not specific (and, thus, requires our vigilance).
    • Symptoms appear 3-12 days after bite
    • For patients who end up with severe disease, incubation is shorter (< 5 days).
  • Initial symptoms include sudden onset of: [Biggs, 2016]
    • Fever, chills
    • Headache
    • Malaise, myalgia, anorexia
    • Nausea, vomiting, and abdominal pain
    • Photophobia
  • Rash?* [Biggs, 2016]
    • Begins as small, blanching pink macule on ankles, wrists/forearms.
      • Then rash spreads to palms, soles, and up extremities.
      • Spares the face.
    • As illness progresses, the rash can develop associated petechiae(days 5-6).
    • Triad of Fever, Rash, and Tick Exposure is not commonly seen initially.
      • < 50% have a rash present within first 3 days of illness.
      • Rash typically appears 2-4 days after onset of fever, so patients may seek care before rash develops.
      • Some children will never develop a rash.
    • Eschar or ulcerative lesion may be present when associated with other SFG illness (ex, R. parkeri).

*Be sure and review Rash?, Dr. Fox’s post Pediatric Rash. This post is simply the best summary on how to safely diagnose and manage pediatric rashes that I have ever read. Thank you, Dr. Fox!

RMSF Late-stage Findings

  • RMSF leads to a systemic vasculitis, so multiple organs can be involved.
    • Meningoencephalitis
    • Acute Renal Failure
    • ARDS
    • Shock
    • Arrhythmia
    • Cutaneous necrosis
  • May become look similar to other conditions like Kawasaki or thrombocytopenic purpura.[Biggs, 2016]

RMSF Lab Findings

  • Common lab abnormalities include:
    • Thrombocytopenia (consumptive)
    • Hyponatremia (due to secretion of ADH and hypovolemia)
    • Increased (slightly) LFTs
    • Increased immature neutrophils
  • Lab findings are often normal early on in illness (so won’t help make the diagnosis early, when it needs to be treated).
  • Diagnostic tests for RMSF is not helpful during early stages of illness.

RMSF Treatment

  • Let’s make this simple… treatment is Doxycycline.
    • For kids <45 kg; dose = 2.2mg/kg Twice a Day
    • For patients >45 kg; dose = 100 mg Twice a Day
    • Treat for at least 3 days AFTER resolution of fever
  • Without appropriate therapy, RMSF progresses rapidly.
    • Early, empiric therapy is the best way to prevent RMSF progression. [Biggs, 2016]
    • Delays in diagnosis associated with:
      • Early presentation
      • Late-onset (or absence) of rash
      • Absence of headache (accentuation of GI symptoms)
  • Unfortunately, many providers often think Doxycycline cannot be given to children <8 years of age. [Zientek, 2014; O’Reilly, 2002]
    • Concerns for dental staining or enamel hypoplasia are often cited as reason to not use Doxycycline.
    • Doses appropriate for RMSF treatment have proven to be safe in children. [Todd, 2015].

Moral of the Morsel

  • RMSF is deadly, but initially presents with non-specific symptoms, making it challenging to detect.
  • Classic triad of fever, rash, and tick exposure should not be relied upon.
  • Relying on history of tick exposure (often not known) can obscure diagnosis.
  • Doxycycline is safe and effective in children! Don’t worry about the teeth!
  • Treat RMSF empirically!
  • Be vigilant during peak seasons: Summer-time “Headache and Fever” needs to have RMSF on the top of the DDx.


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