Syphilis- that has a highly variable clinical course- is caused by the bacterium Treponema pallidum (Spirochaetaceae). Syphilis can cause long-term complications and/or death if not adequately treated. Severe skin manifestations have been described. Syphilis is primarily sexually transmitted, but transmission by blood transfusion or via the placenta is possible. At the onset of congenital syphilis, T. pallidum is liberated directly into the circulation of the foetus resulting in widespread dissemination.