Treponemes cause diverse clinical manifestations. In patients with acquired venereal syphilis, there is an initial genital tract lesion (primary stage) followed by disseminated lesions (secondary stage) and, in approximately one-third of untreated individuals, cardiovascular and neurologic problems (tertiary stage). Infection during pregnancy (congenital syphilis) may result in fetal death or birth defects. Yaws, pinta, and endemic syphilis, the nonvenereal treponematoses, are usually present as skin or mucous membrane lesions. Soft tissue and bone lesions also can occur with yaws and endemic syphilis.