What symptom might a person with syphilis experience?

A person with syphilis may experience a reddish sore, commonly known as a chancre, which typically appears at the site of infection. This sore is usually painless and represents the primary stage of syphilis, where the bacteria enter the body. The presence of this sore is a key indicator in diagnosing syphilis, as it is one of the earliest visible symptoms.

In the context of the other options, while irregular vaginal bleeding, diarrhea, and pharyngitis can be associated with various other medical conditions or infections, they are not characteristic symptoms of syphilis. The chancre serves as a specific and defining symptom of this sexually transmitted infection, making it crucial for early detection and treatment.