BackgroundSexually transmitted infections (STIs) rates have increased in the last two decades in Western world, including syphilis. Higher rates of syphilis lead to the emergence of atypical or less common manifestations like Follmann's balanitis. Follmann's balanitis is an atypical presentation of primary syphilis characterized as erythematous, erosive lesions on the glans penis.MethodsThe aim of the study is to describe the cases of the Follmann 's diagnosed in Vall d'Hebron-Drassanes STI Unit over 20 years (2003-2023). Retrospectively, the epidemiological, clinical and microbiological data were collected.ResultsIn total 20 cases of Follmann's balanitis were diagnosed. The clinical presentation was heterogeneous, with erosive balanitis being the most frequent presentation. Fifteen per cent had also a chancre and 50% presented with lymphadenopathy. Dark field microscopy and Treponema pallidum NAAT were positive in 41% and 92% respectively, and the median RPR titre was 1/4 (IQR 1/2-1/16).ConclusionsFollmann's balanitis is a rare presentation of primary syphilis which has to be suspected in case of erosive balanitis, especially in key populations as MSM or persons with previous STIs, where syphilis is more frequent.