Tertiary syphilis can appear 10 to 20 years after secondary syphilis once it has entered a latent phase. These symptoms can be fatal. Granulomatous lesions or gummas, can develop in mucous membranes, bones and internal organs. They become most deadly if they form in the cardiovascular system or the central nervous system. It can also cause dementia, personality changes, loss of vision, and speech impairment.