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Potentially life-threatening emergency
Rocky Mountain spotted fever in Infant/Neonate
Other Resources UpToDate PubMed
Potentially life-threatening emergency

Rocky Mountain spotted fever in Infant/Neonate

Contributors: Susan Burgin MD, Elena B. Hawryluk MD, PhD, Edith Lederman MD, Noah Craft MD, PhD
Other Resources UpToDate PubMed


Rocky Mountain spotted fever (RMSF) is caused by the gram-negative bacterium Rickettsia rickettsii. It is the most severe rickettsial illness of humans and is difficult to diagnose due to its nonspecific findings. Without treatment, the case fatality rate is 20%-30% with a median time to death of 8 days. Otherwise healthy adults and children have been known to die from the disease.

The disease is spread by ticks (the American dog and Rocky Mountain ticks) via a tick bite or by crushing a tick and transmitting its fecal matter via a mucosal surface (eg, rubbing the eyes). RMSF occurs over a wide distribution throughout the contiguous United States, but cases are most commonly reported from Arkansas, Missouri, North Carolina, Oklahoma, and Tennessee. Over 90% of cases occur during April through September. The disease is more frequent in males; age-specific incidence is highest in children. Overall, the incidence of RMSF has been increasing from 300-800 to 2000 cases per year, but the case fatality rates (at least in the United States) have been decreasing (attributed to enhanced recognition and early treatment).

Early clinical manifestations of RMSF include high fever, severe headache, myalgia, and nausea and vomiting. Later manifestations include rash, photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, and severe abdominal pain. Thrombocytopenia or hyponatremia may be seen. A serious complication of RMSF is rhabdomyolysis. Long-term sequelae include central nervous system deficits and amputations.


A77.0 – Spotted fever due to Rickettsia rickettsii

186772009 – Rocky Mountain spotted fever

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Differential Diagnosis & Pitfalls

  • Acute meningococcemia typically occurs in the late winter to early spring with fever and rash appearing within 24 hours of infection. There is also marked lymphadenopathy.
  • Measles typically occurs in the winter to spring and has associated symptoms of cough, coryza, conjunctivitis, and Koplik spots.
  • Enteroviral infection typically occur in the summer to fall. The fever and rash often appear together. Sick contacts are common.
  • Dengue fever, also known as "breakbone fever," has severe arthralgias.
  • Vasculitis is marked by palpable purpura rather than petechiae.
  • Drug eruptions (Exanthematous drug eruption, Drug-induced non-palpable purpura) will have a history of exposure.
  • Secondary syphilis can also present with a palm and sole rash; occasionally, the rash imparts a rust-colored hue.
  • Disseminated gonorrhea may present with asymmetric monoarticular arthritis and a pustular or petechial rash.
  • Viral or bacterial enterocolitis presents with nausea and vomiting.
  • Acute surgical abdomen has severe abdominal pain.
  • Hepatitis presents with jaundice.
  • Meningitis has prominent neurological signs.
  • Immune thrombocytopenic purpura (ITP) presents with a petechial rash.
  • Thrombotic thrombocytopenic purpura (TTP) is characterized by fever, anemia, thrombocytopenia, renal impairment, and neurological deficits.

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Last Reviewed:08/14/2018
Last Updated:08/16/2018
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Potentially life-threatening emergency
Rocky Mountain spotted fever in Infant/Neonate
A medical illustration showing key findings of Rocky Mountain spotted fever : Abdominal pain, Headache, Nausea/vomiting, Tick bite, Arthralgia, Myalgia, Splenomegaly, High fever, PLT decreased
Clinical image of Rocky Mountain spotted fever - imageId=273650. Click to open in gallery.  caption: 'Myriad petechiae on the arm.'
Myriad petechiae on the arm.
Copyright © 2024 VisualDx®. All rights reserved.