In which phase of syphilis might a person experience skin rashes and mucous membrane lesions?

The phase of syphilis characterized by skin rashes and mucous membrane lesions is the secondary stage. During this phase, the infection makes its presence known throughout the body, leading to systemic symptoms. The rash typically appears as reddish-brown spots and can be found on various parts of the body, including the trunk and extremities. Additionally, mucous membrane lesions, known as mucous membrane pemphigoid or "snail-track" ulcers, can appear in the oral cavity and on the genitals. These symptoms arise as the Treponema pallidum bacterium spreads throughout the body after the initial infection in the primary phase.

Recognizing the symptoms associated with the secondary phase is critical for timely diagnosis and treatment, preventing progression to more severe stages of the infection, such as the tertiary phase, where more serious complications may develop. The tertiary phase is not associated with the same types of skin and mucous membrane lesions but rather with systemic health issues potentially affecting the heart, brain, and other organs. The concept of a quaternary stage is not part of the standard classification of syphilis.