[Late congenital syphilis: case report].

Syphilis shows marked increase in its prevalence in Argentina and the world. The World Health Organization estimates that annually there are 12 million people infected in the world, 270,000 corresponding to newborns with congenital syphilis. We describe an 8-year-old girl who was undergoing mononucleosis due to Epstein-Barr virus and presented syphilis as a diagnostic finding, confirmed by two different positive treponemal tests, assuming a compatible picture of late latent congenital asymptomatic syphilis.