Cutaneous Eruption in a Crohn's Disease Patient Under Tumor Necrosis Alpha Inhibitor Treatment: A Rare Case of Syphilis.

Reaching a diagnosis of a cutaneous eruption in a Crohn's disease (CD) patient treated with anti-tumor necrosis factor alpha (anti-TNFα) can be challenging. Differential diagnosis must include extra-intestinal manifestations of CD, adverse reactions to the therapy itself as well as infectious diseases with cutaneous manifestations. We report the case of a 28-year-old man on infliximab for Crohn's colitis, who presented with painless, non-pruritic genital and body exanthema. After a thorough evaluation, early secondary syphilis was confirmed with a fluorescent treponemal antibodies-absorbed test. Intramuscular (IM) benzathine penicillin G 2.4 million units in a single dose was administered and clinical manifestations resolved completely within a couple of weeks.