Rocky Mountain Spotted Fever: When Symptoms Don’t Look Typical

Rocky Mountain spotted fever symptoms can vary—and atypical presentations may delay diagnosis.

Although RMSF is most commonly reported in Missouri, Tennessee, Oklahoma, Arkansas, and North Carolina, cases occur across the United States.

Transmission varies by region:

• Eastern U.S.: American dog tick
• Rocky Mountains: Rocky Mountain wood tick
• Southwestern U.S.: Brown dog tick

Clinical reality: geographic variability can complicate recognition.

Atypical Case: Not the Classic Presentation

In a case reported by Hussain and colleagues, a 71-year-old man presented with:

• Fever
• Generalized weakness and muscle pain
• Persistent hiccups

Within days, his condition worsened, progressing to confusion and agitation.

Clinical pattern: neurologic symptoms may dominate early presentation.

Initial Improvement—Then Sudden Decline

The patient initially improved after treatment for presumed sepsis, including IV ceftriaxone.

However, he later developed a high fever of 106.5°F and required ICU care.

Key issue: early improvement can be misleading.

Exposure History Changes the Diagnosis

Further questioning revealed recent exposure to ticks and a cat suspected of carrying lice.

He was tested for multiple infections, including:

• Rickettsia
• Borrelia burgdorferi
• Bartonella

Testing later confirmed Rickettsia infection.

Empiric doxycycline was started—and proved critical.

[bctt tweet=”Rocky Mountain spotted fever may present without classic symptoms—early doxycycline can be life-saving.” username=”DrDanielCameron”]

Why Early Treatment Matters

Delays in treatment—especially within the first five days—are associated with increased mortality.

Diagnostic confirmation is often not available early in the illness.

Clinical takeaway: treatment decisions must be based on suspicion, not waiting for test results.

Lessons from This Case

• RMSF may present without a rash or persistent fever
• Neurologic symptoms such as confusion can be prominent
• Symptoms may temporarily improve before worsening
• Tick exposure may not be recalled initially

Clinical pattern: atypical presentations can delay diagnosis and treatment.

Clinical Takeaway

Rocky Mountain spotted fever symptoms may be subtle, atypical, or evolving.

Clinicians should maintain a high index of suspicion—especially in endemic areas or when patients present with unexplained febrile or neurologic illness.

Empiric doxycycline should not be delayed.

Key question: Could an unexplained febrile or neurologic illness be RMSF—even without a rash?

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention