A Case of Jarisch-Herxheimer Reaction After Ceftriaxone Initiation for Lyme Carditis in Postpartum Female.

Lyme carditis is a complication occurring in 1%-5% of Lyme disease infections. It can lead to life-threatening cardiac conduction abnormalities. Treatment with antibiotics may trigger the Jarisch-Herxheimer reaction (JHR), an acute inflammatory response to spirochetal lysis. Here, we present a 32-year-old postpartum female with complete heart block and disseminated erythema migrans who developed JHR within hours of ceftriaxone initiation, requiring vasopressor support. Hemodynamic instability resolved within 24 h, with subsequent normalization of cardiac conduction within 72 h. This case highlights the importance of recognizing JHR, distinguishing it from allergic reactions and septic shock, and avoiding unnecessary antibiotic discontinuation.