What are the symptoms of Rocky Mountain spotted fever?

Symptoms of Rocky Mountain Spotted Fever

Rocky Mountain spotted fever (RMSF) typically presents with fever, headache, and a characteristic rash that begins as small pink macules on the extremities and spreads to involve the palms and soles, often becoming petechial as the disease progresses. 1

Initial Symptoms (Days 1-4)

• Fever: Sudden onset, often high-grade
• Headache: Often severe
• Myalgia: Generalized muscle pain
• Malaise and chills
• Gastrointestinal symptoms:
  • Nausea and vomiting
  • Abdominal pain (may mimic appendicitis)
  • Anorexia
  • Diarrhea
• Other early symptoms:
  • Photophobia
  • Conjunctival suffusion
  • Periorbital edema (more common in children)

Rash Development (Days 2-5)

• Appears 2-4 days after fever onset in most patients
• Progression pattern:
  1. Small (1-5 mm) blanching pink macules initially on wrists, ankles, and forearms
  2. Spreads to palms, soles, arms, legs, and trunk (usually sparing the face)
  3. Evolves to maculopapular rash
  4. May develop central petechiae
  5. Can become generalized petechial rash by days 5-6

Important Clinical Considerations

• The classic triad of fever, rash, and reported tick bite is present in only a minority of patients at initial presentation 1
• Absence of rash should not rule out RMSF:
  • <50% of patients have a rash in the first 3 days
  • Some patients never develop a rash (up to 20%) 2
  • Lack of rash is associated with delayed diagnosis and increased mortality 1
• Rash characteristics may vary:
  • May be atypical, localized, faint, or evanescent
  • More difficult to recognize in persons with darker skin pigmentation
  • Children more frequently have rash than adults and develop it earlier 1

Late-Stage Manifestations (Days 5+)

If untreated, severe manifestations may develop:

• Neurologic:
  • Meningoencephalitis
  • Focal neurologic deficits
  • Seizures
• Cardiovascular:
  • Shock
  • Arrhythmias
• Respiratory: Acute respiratory distress syndrome (ARDS)
• Renal: Acute renal failure
• Cutaneous: Necrosis and gangrene
• Hematologic: Thrombocytopenia, DIC-like coagulopathies

Laboratory Findings

• Thrombocytopenia
• Slightly increased hepatic transaminase levels
• Normal or slightly increased white blood cell count with increased immature neutrophils
• Hyponatremia

Critical Timing and Mortality

• Case-fatality rate: 5-10% overall 1
• Delay in diagnosis and treatment is the most important factor associated with increased mortality
• Patients treated after the fifth day of illness have significantly higher mortality rates
• The frequency of hospitalization, ICU admission, and death increases with delay in appropriate treatment 1

Common Pitfalls

• Waiting for the classic triad before considering diagnosis (present in only a minority of cases)
• Delaying treatment while awaiting laboratory confirmation (increases mortality)
• Overlooking RMSF in patients with:
  • Absence or late onset of rash
  • Nonspecific gastrointestinal symptoms
  • Atypical rash patterns
• Assuming rash on palms and soles is exclusive to RMSF (can occur in other conditions) 2

Early recognition of symptoms and prompt initiation of appropriate antibiotic therapy (doxycycline) are essential to prevent severe complications and death from RMSF.