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.