Oral mucosal lesions presenting as erythematous patches usually pose difficulties for a clinical diagnosis. They elicit an array of differential diagnosis that mainly includes oral candidosis, contact mucosal reaction, oral lichenoid lesion, oral psoriasiform, autoimmune disease, and, not to forget, secondary syphilis. In this present case, all those above-mentioned possibilities were ruled out, while secondary syphilis stood as the main diagnosis. As this was also later excluded by a negative serological treponemal test, the final diagnosis rested on an ectopic manifestation of benign migratory glossitis (BMG), whose diagnosis was based on the clinical aspects of the lesions, along with their spontaneous disappearance in a short period of time (a hallmark of this condition) and the presence of fissured tongue, a manifestation that occurs very often in concomitance with BMG.