What is a characteristic symptom of primary syphilis?

A characteristic symptom of primary syphilis is a painless ulcer, also known as a chancre. This ulcer typically appears at the site where the syphilis bacteria, Treponema pallidum, entered the body, which may often be on the genitals, anus, or mouth. The chancre is usually firm, round, and without pain, making it distinct from ulcers caused by other conditions.

This painless presentation is key to the identification of primary syphilis, as many patients may not initially seek treatment because the chancre is not causing them discomfort. It usually resolves on its own within a few weeks, but it is important to note that this does not indicate the infection has cleared; rather, the disease can progress to secondary syphilis if not treated.

In contrast, painful ulcers are more typical of conditions such as herpes simplex virus infections or chancroid. Flu-like symptoms are often associated with the secondary stage of syphilis rather than the primary stage, where the chancre is the primary focus. Skin rashes are also associated with secondary syphilis and occur later in the infection. Thus, the painless ulcer is the hallmark symptom that is specifically characteristic of primary syphilis.