IS IT A HERXHEIMER REACTION OR ANAPHYLAXIS COMPLICATING USE OF PENICILLIN IN SYPHILIS TREATMENT?

Abstract

<h3>Introduction</h3> Herxheimer reactions, similar to anaphylaxis, can occur after the first dose of penicillin and can be associated with dyspnea, hypotension, rash, vomiting and tachycardia. Herein we describe a case regarding a complication of syphilis treatment that was thought to be anaphylaxis, but further investigation suggested Herxheimer reaction. <h3>Case Description</h3> A 62-year-old man with a distant history of syphilis infection was seen by an outpatient ophthalmologist for 1.5 months of rapidly worsening vision in his right eye secondary to ocular syphilis. RPR testing was positive and the patient was directly admitted for treatment. The patient reported developing a reaction to penicillin more than thirty years prior which included vomiting, dyspnea, throat tightening, and a rash fitting the description of urticaria that was reflexively diagnosed as anaphylaxis at the time. Due to the 30-year history of penicillin allergy, the Allergy Immunology Service was consulted. The patient passed the indicated penicillin skin testing and challenge. On further evaluation, it was determined that he previously had rigors, fever, and chills, which were more compatible with Herxheimer Reaction. He was then started on penicillin G 4MU IV q4 hours. Fortunately, he did not develop an "ocular" Herxheimer reaction. <h3>Discussion</h3> Distinguishing anaphylaxis from a Herxheimer reaction in this patient is important for several reasons: (1) treatment can cause an ocular Herxheimer reaction, (2) avoidance of penicillin for 30 years may have led to delayed, more expensive, and less effective therapies, and (3) the cost of skin testing, challenge, and if-needed desensitization could have been avoided based on the history.