UMEM Educational Pearls


A patient presents with the rash shown below and is treated with penicillin. Fever, headache, and myalgia develop four hours later. What’s the diagnosis?


Answer: Jarisch-Herxheimer reaction

  • Reaction observed 2-8 hours following antibiotic treatment of syphilis as a result of endotoxin released from dying from organisms; it is not an allergy to penicillin, nor a dose related phenomenon.
  • Symptoms may include:
    • Fever / chills / rigors
    • Headache
    • Flushing / Vasodilation
    • Worsening rash
    • Hypotension
  • Can occur when following treatment of any stage of syphilis although most commonly occurs following treatment of primary syphilis; also with other illnesses caused by spirochetes (Lyme, Leptospirosis, etc.)
  • Reaction is typically self-limiting and treatment is supportive care


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