Which phase of syphilis involves the development of a chancre?

The development of a chancre is a hallmark of the primary phase of syphilis. This initial sore typically appears at the site where the syphilis bacteria, Treponema pallidum, entered the body, commonly on the genitals, anus, or mouth. The chancre is usually painless and can go unnoticed, but it is an important indicator of an initial syphilis infection. In the primary phase, the immune system has not yet mounted a significant response, which allows the bacteria to establish an infection. Recognizing this phase is crucial for early diagnosis and treatment, which can prevent the progression to later, more severe stages of the disease.