Symptoms of Rickettsial Disease
Rickettsial diseases typically present with nonspecific early symptoms of fever, headache, malaise, and myalgia, with rash appearing later in the course—but the absence of rash should never exclude the diagnosis, as less than 50% of patients have rash in the first 3 days and some never develop it at all. 1
Early Clinical Presentation (First 3-5 Days)
Common Initial Symptoms
Additional Early Symptoms
- Nausea or vomiting 1
- Abdominal pain (may mimic appendicitis, cholecystitis, or gastroenteritis) 1
- Anorexia 1
- Photophobia 1
- Diarrhea 1
Critical pitfall: The classic triad of fever, rash, and tick bite is present in only a minority of patients at initial presentation, so do not wait for this triad to consider rickettsial disease. 1
Cutaneous Manifestations (Variable Timing and Presentation)
Rocky Mountain Spotted Fever (RMSF)
- Rash typically appears 2-4 days after fever onset 1
- Initial rash: Small (1-5 mm) blanching pink macules on ankles, wrists, or forearms 1
- Progression: Spreads to palms, soles, arms, legs, and trunk (usually sparing face), becoming maculopapular with central petechiae 1
- Classic petechial rash involving palms and soles appears by day 5-6, indicating advanced disease 1
- Eschar is rarely present with RMSF (unlike other spotted fever group rickettsioses) 1
Important caveat: Less than 50% of patients have rash in the first 3 days, and some patients never develop rash—absence of rash is associated with delayed diagnosis and increased mortality. 1
Other Spotted Fever Group Rickettsioses
- Rickettsia parkeri: Eschar present, sparse maculopapular or vesiculopapular rash involving palms and soles 1
- Rickettsia species 364D: Eschar or ulcerative lesion with regional lymphadenopathy 1
Ehrlichioses
- E. chaffeensis (human monocytic ehrlichiosis): Rash in approximately 30% of adults and 60% of children, appearing median 5 days after illness onset 1
- E. ewingii: Rash rare 1
- E. muris-like agent: Rash in approximately 12% 1
Anaplasmosis
- Rash rare, occurring in less than 10% of cases 1
Additional Clinical Features
Pediatric-Specific Findings
- Periorbital and peripheral edema (more common in children) 1
- Children aged <15 years develop rash more frequently and earlier than adults 1
Other Associated Symptoms
Severe Late-Stage Manifestations (Untreated Disease)
These indicate advanced disease with high mortality risk: 1
- Meningoencephalitis 1
- Acute renal failure 1
- ARDS (acute respiratory distress syndrome) 1
- Cutaneous necrosis and gangrene 1
- Shock 1
- Arrhythmia 1
- Seizure 1
- Focal neurologic deficits (cranial or peripheral motor nerve paralysis) 1
Timing and Incubation Periods
- RMSF: 3-12 days after tick bite (shorter incubation period of ≤5 days associated with severe disease) 1
- Ehrlichiosis: 5-14 days after tick bite 1
- Anaplasmosis: 5-14 days after tick bite 1
- R. parkeri: 2-10 days after tick bite 1
Common Laboratory Findings
RMSF
- Thrombocytopenia 1
- Slightly increased hepatic transaminase levels 1
- Normal or slightly increased white blood cell count with increased immature neutrophils 1
- Hyponatremia 1
Ehrlichiosis
Anaplasmosis
- Thrombocytopenia 1
- Leukopenia 1
- Mild anemia 1
- Increased hepatic transaminase levels 1
- Increased numbers of immature neutrophils 1
Critical Clinical Pearls
Maintain high clinical suspicion for rickettsial disease in any nonspecific febrile illness during spring and summer months, especially with tick exposure history. 1 However, over one-third of patients do not recall tick exposure. 2
Delay in diagnosis and treatment is the most important factor associated with increased mortality—patients treated after day 5 of illness have significantly higher mortality than those treated earlier. 1
Do not wait for rash development or the classic triad before initiating empiric doxycycline therapy, as early treatment is critical for preventing progression and reducing mortality. 1, 3