Primary chancre (ulcer) on a man's penis due to syphilis. This sexually transmitted disease is caused by the Treponema pallidum bacterium. The first symptom is this chancre at the site of infection. This heals after a month or two, and the second stage starts up to a month after this. Secondary syphilis is characterised by a rash, headaches, pain in the bones and fatigue. This eventually subsides, and the patient appears normal. The latent stage may last for years, even decades, but can progress to tertiary syphilis. Tissue destruction then leads to vascular disease and paralysis due to brain damage. At all stages, treatment is with penicillin antibiotic drugs.