Rocky Mountain spotted fever (RMSF) is a serious, potentially life-threatening tick-borne illness caused by Rickettsia rickettsii that presents with fever, headache, myalgia, and rash and is treated with doxycycline for 5–10 days.
Physical Exam Findings
General: Appears ill, febrile. May exhibit lethargy or restlessness.
Skin: Rash noted, starting on wrists and ankles, with centripetal spread to trunk, face, and extremities. Rash may be macular, maculopapular, or petechial.
HEENT:
- Eyes: May have conjunctival injection.
- Mouth: Mucous membranes may be dry if dehydrated.
Neck: May have meningismus (nuchal rigidity).
Lungs: May exhibit crackles if pulmonary involvement (e.g., edema or ARDS).
Abdomen: Diffuse tenderness may mimic an acute abdomen.
Extremities: May have peripheral edema or cyanosis in severe cases. Rash may extend to palms and soles.
Musculoskeletal: Myalgia may be present.
Neurologic: Altered mental status or seizures may be noted in severe cases.
Psychiatric: May appear confused or disoriented in severe cases.
1. First-Line Treatment
- Doxycycline is the treatment of choice for all patients, regardless of age or pregnancy status.
- Adults: 100 mg orally or IV twice daily for at least 7 days and until the patient has been afebrile for 48–72 hours.
- Children: 2.2 mg/kg per dose twice daily (maximum 100 mg per dose).
- Note: Doxycycline use in children is supported because the benefits of timely treatment outweigh concerns about tooth discoloration.
2. Alternative Treatment
- Chloramphenicol is an alternative in rare cases where doxycycline is contraindicated, such as severe allergies.
- Adults: 50 mg/kg/day divided into 4 doses.
- Children: 50–75 mg/kg/day divided into 4 doses.
- Limitations: Chloramphenicol is associated with a higher risk of adverse effects (e.g., aplastic anemia) and inferior efficacy compared to doxycycline.
- Wu, J., Dotters-Katz, S. K., & Varvoutis, M. (2024). “Atypical Presentation of Rocky Mountain Spotted Fever inPregnancy.” American Journal of Perinatology Reports, 14(1), e40–e42. This case report describes an atypical presentation of RMSF in the third trimester, highlighting diagnostic challenges and treatment with doxycycline.
- Licona-Enriquez, J. D., Delgado-de la Mora, J., Paddock, C. D., Ramirez-Rodriguez, C. A., Candia-Plata, M. D. C., & Hernández, G. Á. (2017). “Rocky Mountain Spotted Fever and Pregnancy: Four Cases from Sonora, Mexico.” The American Journal of Tropical Medicine and Hygiene, 97(3), 795–798. This study reports on four pregnant women with RMSF in Sonora, Mexico, discussing clinical presentations and outcomes.
- Stallings, S. P. (2001). “Rocky Mountain Spotted Fever and Pregnancy: A Case Report and Review of the Literature.” Obstetrical & Gynecological Survey, 56(1), 37–42. This article presents a case report and literature review on RMSF during pregnancy, discussing diagnostic challenges and treatment considerations.
- Curtis, M. W., & Lopez, J. E. (2024). “Tick-Borne Diseases and Pregnancy: A Narrative Review Evaluating PregnancyComplications Caused by Tick-Borne Diseases.” Tropical Medicine and Infectious Disease, 9(11), 254. This review evaluates pregnancy complications caused by various tick-borne diseases, including RMSF.
- Gallis, H. A. (1985). “Rickettsial Diseases in Pregnancy.” In N. Gleicher (Ed.), Principles of Medical Therapy in Pregnancy (pp. 526–528). Springer, Boston, MA. This book chapter discusses various rickettsial diseases during pregnancy, including RMSF, focusing on clinical features and management.
- Biggs, H. M., Behravesh, C. B., Bradley, K. K., Dahlgren, F. S., Drexler, N. A., Dumler, J. S., Folk, S. M., Kato, C. Y., Lash, R. R., Levin, M. L., & Paddock, C. D. (2016). “Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis—UnitedStates.” MMWR Recommendations and Reports, 65(2), 1–44. This comprehensive guideline provides recommendations for the diagnosis and management of tickborne rickettsial diseases, including RMSF, in the United States.
