Tx:Penicillin G. Watch for Jarisch-Herxheimer reaction.
Borrelia burgdorferi (Lyme Disease)
Vector:Ixodes tick.
Stage 1:Erythema migrans (bull’s-eye rash).
Stage 2:Bilateral facial nerve (CN VII) palsy, AV block.
Stage 3:Migratory monoarthritis (esp. knee).
Tx:Doxycycline. Use Ceftriaxone for severe/late disease.
Leptospira interrogans (Leptospirosis)
Source: Water contaminated with animal urine.
Sx: Flu-like, severe myalgias (calves), conjunctival suffusion (red eyes, no exudate).
Weil’s Disease: Severe form with jaundice, renal failure, and hemorrhage.
Tx:Doxycycline or Penicillin G.
Jarisch-Herxheimer reaction
Definition & Etiology
Acute, self-limiting systemic reaction occurring shortly after the initiation of antibiotic treatment for spirochetal infections.
Most classically associated with the treatment of Syphilis (Treponema pallidum).
Also seen in Lyme disease (Borrelia burgdorferi) and Leptospirosis.
Pathophysiology
Rapid lysis of spirochetes releases bacterial lipoproteins, endotoxins, and pyrogens into the bloodstream.
Triggers a massive cytokine storm (TNF-α, IL-6, IL-8).
Clinical Features
Onset: Typically occurs 6–24 hours after the first dose of antibiotics (e.g., Penicillin G).
Symptoms: Flu-like presentation:
Fever, chills, rigors.
Headache, myalgias.
Tachycardia, hypotension (vasodilation).
Exacerbation of skin lesions (e.g., chancre or rash becomes more prominent).
Differential Diagnosis
Antibiotic Hypersensitivity (Allergy): Differentiate based on timing and sx.
JHR: Fever/constitutional sx, occurs within hours, no urticaria/wheezing.
Allergy: Urticaria, pruritus, angioedema, anaphylaxis; may occur immediately or days later.
Sepsis: If hypotension is severe (though JHR is usually transient).
Management
Supportive Care: Antipyretics (Acetaminophen/NSAIDs), IV fluids for hypotension.
Continue Antibiotics: Do NOT stop the offending antibiotic. The reaction is self-limiting and resolves within 12–24 hours.
Pregnancy: Pregnant women treated for syphilis should be monitored for preterm labor and fetal distress during JHR.
USMLE Pearl
Be careful not to confuse this with a Penicillin allergy. A vignette will describe a patient treated for syphilis who develops fever and shakes 6 hours later. The correct answer is to continue therapy and observe, not switch to Doxycycline or give Epinephrine.