Syphilis is a systemic disease caused by the spirochete Treponema pallidum. Due to its many protean clinical manifestations, it has been named the “great imitator and mimicker.” Treponemes are helically coiled, corkscrew-shaped cells, 6 to 15um long and 0.1 to 0.2 um wide. They have an outer membrane which surrounds the periplasmic flagella, a peptidoglycan-cytoplasmic membrane complex, and a protoplasmic cylinder.
Syphilis is considered a sexually transmitted disease, as most cases are transmitted through vaginal, anogenital, and orogenital contact. The infection can rarely be acquired via non sexual contacts, such as skin to skin, or via blood transfer (blood transfusion or needle sharing). Vertical transmission occurs transplacentally, resulting in congenital syphilis.
The disease has been divided into stages on the basis of clinical findings, which guide the treatment and follow up. The primary syphilis appears 10-90 days after the exposure to the infection and comprises a painless ulcer or chancer at the site of infection with T. Pallidum. The Secondary syphilis appears 2-8 weeks after disappearance of chancer and has multiple systemic manifestations that can involve any system and body part. The secondary syphilis manifestation can include skin rash, mucocutaneous lesion, and lymphadenopathy. Untreated primary or secondary syphilis is followed by an early latent phase (one year or less later on) or late latent phase (over one year) and is characterized by positive serologic tests but negative clinical manifestations. Similarly, tertiary syphilis is late symptomatic syphilis that can manifest months or years after the initial infection and can present with cardiac involvement, gummatous lesion, tabes dorsalis, and general paresis.
Congenital syphilis results from transplacental transmission or contact with infectious lesions during birth and can be acquired at any stage, causing stillbirth or neonatal congenital infection.