Syphilis is divided into acquired syphilis and congenital syphilis, which is transmitted via the fetus. Acquired syphilis, based on the duration of the disease and using two years as a boundary, is further divided into early-stage syphilis and late-stage syphilis. Early-stage syphilis, particularly primary syphilis, mainly presents symptoms such as a chancre and scleradenitis, generally without systemic symptoms. Secondary syphilis occurs when primary syphilis is untreated or not completely treated, allowing the virus to enter the bloodstream from the lymphatic system and spread throughout the body. This causes damages to the skin, mucous membranes, and systemically, known as secondary syphilis. It can manifest as various forms of syphilitic rash, some resembling papular rashes, others similar to dermatitis, eczema, flat lichen, urticaria, psoriasis, pustular disease, and others. Some secondary syphilitic rashes are similar to flat genital warts, and sometimes syphilis can lead to alopecia. Syphilis can also affect mucous membranes, appearing in the mouth, tongue, pharynx, larynx, and genital mucous membranes, characterized by one or more areas of distinct erythema, vesicles, erosion, covered with a grayish-white membrane, generally painless. Some syphilis cases might affect bones, causing damage to bones and joints. Latent syphilis presents no obvious symptoms, and late-stage syphilis might involve the cardiovascular and nervous systems.