Within 2 hours of receiving the first dose of intravenous penicillin, a patient being treated for severe leptospirosis develops rigors, a spike in temperature, hypotension, and worsening tachycardia. What is the mechanism of this reaction?

• A IgE-mediated mast cell degranulation to penicillin determinants
• B Release of endotoxin-like lipoproteins from mass killing of spirochaetes ✓
• C Immune complex deposition triggering complement activation
• D Direct toxic effect of penicillin on vascular endothelium

Explanation

The Jarisch-Herxheimer reaction is an acute exacerbation of fever, rigors, hypotension, and tachycardia shortly after starting therapy for spirochaetal infections such as syphilis, leptospirosis, and relapsing fever. It results from cytokine release driven by lipoproteins liberated from rapidly killed spirochaetes, not from IgE allergy, immune complexes, or direct drug toxicity. Management is supportive with fluids and antipyretics, and treatment should continue.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.