A 24-year-old woman with secondary syphilis receives her first dose of intramuscular benzathine penicillin. Two hours later she develops rigors, high fever, hypotension and intensification of her rash. The most likely mechanism of this reaction is:

• A Massive lysis of treponemes releasing lipoproteins that provoke a cytokine surge ✓
• B Immune complex deposition triggering complement activation
• C IgE-mediated type I hypersensitivity to penicillin degradation products
• D Direct toxic effect of benzathine on cardiac conducting tissue

Explanation

This is the Jarisch-Herxheimer reaction, an acute febrile reaction occurring within hours of starting effective antisyphilitic therapy. Killing of large numbers of treponemes releases treponemal endotoxin-like lipoproteins, which trigger TNF-alpha, IL-6 and IL-8 release, causing fever, chills, headache and hypotension. It is self-limiting and managed supportively with antipyretics and fluids; it must not be mistaken for penicillin allergy, which would preclude further doses of first-line therapy.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.