Follmann's balanitis: An heterogeneous clinical manifestation of primary syphilis.

This article focuses on Follmann's balanitis (FB), a rare and atypical presentation of primary syphilis characterized by erythematous, erosive lesions on the glans penis. A retrospective study conducted at the Vall d'Hebron-Drassanes STI Unit in Barcelona identified 20 cases of FB over 20 years (2003–2023), representing a prevalence of 5.5 per 1,000 early syphilis infections. Most patients were cisgender men who have sex with men (MSM), with heterogeneous clinical presentations including erosive balanitis, occasional chancres, and lymphadenopathy; diagnostic confirmation relied on dark field microscopy, Treponema pallidum nucleic acid amplification tests (NAATs), and serology. The study highlights the importance of considering FB in differential diagnosis of erosive balanitis, especially among key populations with higher syphilis rates, as its clinical features and serological responses may differ from typical primary syphilis.