Syphilis is a Rare Cause of Erythema Nodosum: A Case Report

Erythema nodosum (EN) is a dermatological manifestation, the common etiologies of which are already widely described. Here, we report the case of a patient who presented an EN, where the etiology was found to be a rare diagnosis: syphilis, a sexually transmitted infection with various clinical presentations. A 42-year-old female patient without any medical condition presented with a clinical picture associating a maculopapular rash at first, and later on a well-defined hypodermic lesion, clinically suggestive of an EN, on the right forearm. The etiologic workup ruled out sarcoidosis, which was the first suspected diagnosis. Positive VDRL-TPHA and recovery within 15 days after benzathine benzylpenicillin administration allowed the diagnosis of syphilis to be made on the EN. EN is a rare manifestation of syphilis that should be kept in mind in these times of strong recrudescence of the disease among men who have sex with men in mainland France but also among heterosexuals in Reunion Island.

Automated summary

This article reports a case of erythema nodosum (EN) with a rare etiology of syphilis. The patient presented with a maculopapular rash and a hypodermic lesion, which were further investigated and ruled out other possible causes. The diagnosis of syphilis was made based on positive results and recovery after treatment. It is important to consider EN as a rare manifestation of syphilis, especially in the context of increasing cases among men who have sex with men in mainland France and heterosexuals on Reunion Island.