The etiologic agent of syphilis is the spirochete Treponema pallidum. The organism is motile and can be observed moving about under the dark- field microscope. It is extremely difficult to cultivate in the laboratory, and direct observation is usually required for diagnosis. The organism is transmitted among humans by sexual contact, such as during sexual intercourse.
The development of syphilis is generally an involved series of events. The primary stage consists of a painless, hard sore called a chancre at the site where spirochetes have entered the body(usually on the external or internal genital organs). After several weeks, the chancre disappears and a latent period ensues. The secondary stage appears many weeks or months later. The secondary stage is accompanied by a skin rash with pustular lesions and skin eruptions. The hair on the head and eyebrows is often lost. Liver inflammation is common, and an influenza like syndrome may appear. The person is highly contagious at this point. After some time, the lesions heal and another latent stage develops. A tertiary stage may appear years later. This stage is characterized by the formation of gummas, which are gummy, granular lesions that form in the brain and major blood vessels. The patient often becomes paralyzed and usually suffers permanent damage to the blood vessels. In addition, the symptoms of dementia may occur. Death usually accompanies destruction of the heart and blood vessel tissues.
One of the dangers of syphilis is the possible development of congenital syphilis. In this instance, the spirochetes cross the placenta and enter the fetal blood from the mother’s blood. Newborns show signs such as notched incisors (Hutchinson’s teeth), a perforated palate, an aged- looking face, and damage to the nose. Congenital syphilis may also result in stillbirth.