RMSF in Pregnancy Without Rash: A Missed Diagnosis Risk
No rash. No tick bite
Symptoms escalate quickly
Diagnosis is often delayed
RMSF in pregnancy is a high-risk condition that may present without classic signs, making diagnosis particularly challenging.
A 37-year-old woman at 31 weeks gestation was admitted with severe headaches and a persistent fever lasting one week.
She had recently traveled and hiked outdoors in Washington but did not recall a tick bite or notice a rash.
This presentation reflects a broader pattern seen in tick-borne illness, where symptoms do not always follow expected patterns, similar to challenges described in Lyme disease misdiagnosis.
Here’s how this case unfolded.
Initial Symptoms and Clinical Presentation
In addition to headache and fever, the patient developed:
- Night sweats
- Chills
- Dyspnea
- Diarrhea
Despite these symptoms, there was no rash—one of the hallmark signs typically associated with RMSF.
This pattern is often missed because clinicians expect a rash or clear tick exposure.
The absence of classic features can delay recognition and treatment.
Initial Misdiagnosis
The patient was initially treated for atypical HELLP syndrome, a life-threatening pregnancy complication related to preeclampsia.
However, her condition rapidly worsened.
Within six hours of starting antibiotics, she developed:
- Severe tachypnea
- Tachycardia
- Persistent fever
Her clinical decline required intubation and an emergency cesarean section.
Diagnosis: RMSF in Pregnancy Confirmed
After reevaluation, RMSF became the leading diagnosis based on:
- Fever, headache, and malaise
- Thrombocytopenia
- Elevated liver enzymes
- Rapid clinical deterioration
- Cerebrospinal fluid findings consistent with aseptic meningitis
Doxycycline was initiated after discontinuing vancomycin.
The patient improved following treatment, and the infant was born healthy with no evidence of infection.
Treatment Considerations in Pregnancy
Doxycycline remains the treatment of choice for RMSF.
Although historically avoided in pregnancy, emerging evidence suggests doxycycline may be safer than previously thought—particularly when treating life-threatening infections.
Prompt treatment significantly reduces morbidity and mortality in both mother and child.
For broader context on treating tick-borne infections, see Lyme disease co-infections.
Why This Matters
RMSF in pregnancy can present without the signs clinicians rely on most.
Delays in diagnosis increase the risk of severe complications, including respiratory failure and maternal-fetal distress.
Recognizing atypical presentations is critical in endemic areas.
Clinical Perspective
This case highlights the importance of maintaining a broad differential diagnosis when evaluating pregnant patients with fever and systemic symptoms.
Tick-borne illnesses should be considered even in the absence of rash or known tick exposure.
Early recognition and timely treatment can be lifesaving.
Clinical Takeaway
RMSF in pregnancy is a potentially fatal condition that may present without classic features.
Clinicians should consider RMSF in patients with fever, systemic symptoms, and laboratory abnormalities—even when rash and tick exposure are absent.
Frequently Asked Questions
Can RMSF occur without a rash or tick bite?
Yes. Atypical cases may lack both rash and known tick exposure, making diagnosis more difficult.
Is doxycycline safe during pregnancy?
Emerging evidence suggests doxycycline may be used when benefits outweigh risks, particularly in severe infections like RMSF.
What are the symptoms of RMSF?
Symptoms may include fever, headache, malaise, night sweats, and gastrointestinal symptoms. Laboratory findings often include thrombocytopenia and elevated liver enzymes.
How is RMSF treated?
Doxycycline is the treatment of choice. Early treatment significantly improves outcomes.
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References
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
