Syphilis is a sexually transmitted infection with systemic, devastating clinical manifestations if left untreated. Syphilis is caused by infection with Treponema pallidum, a spirochete. Syphilis has garnered recent media attention as the incidence has been on the rise throughout Europe and the United States.

As reported by the European Centre for Disease Prevention and Control, syphilis infections have been increasing in number in Europe with nearly 25,000 cases being reported in 2014. This data was obtained from 29 EU/EEA Member States (excluding Austria and Liechtenstein), revealing an overall rate of 5.1/100,000.  The population with the greatest increase in infection were men who have sex with men, accounting for 63% of cases. The incidence in 2014 reported by the EDC reflected a 6 times higher incidence in men as compared with women. The most common age of presentation was 25 years or older, with <15% of patients being under the age of 25.  The age group that saw the greatest increase were those patients 45 years of age and older, with nearly 30% of cases occurring in this subgroup.

In the United States, the number of syphilis cases have been on the rise since the early 2000s, with nearly 24,000 cases reported in 2014. In the United States, about 90% of the cases were seen in men who have sex with men and about half were co-infected with HIV. The incidence also increased in heterosexual men, women, and in cases of congenital syphilis.

Syphilis is transmitted by contact with infected lesions, such as a chancre, mucosal lesions, condylomata lata, or skin rashes.  Syphilis may also be transmitted vertically during pregnancy to the fetus. The incubation period is typically 4-6 weeks after which a painless indurated papule develops along with regional lymphadenopathy. In heterosexual men, this lesion typically occurs on the penile shaft, while in homosexual men, the lesion is often more obscure, occurring near the anus, within the anal canal or in the oral cavity.  In women, lesions typically occur on the cervix or labia. The lesion spontaneously resolves over a period of 2-12 weeks; however, the adenopathy typically persists for several months.

Diagnosis at the primary stage is key to prevent complications.  If infection remains undiagnosed, patients progress to secondary and then latent syphilis.  A full discussion of secondary and latent syphilis is outside the scope of this post.  However, untreated latent syphilis can lead to neurologic devastation (neurosyphilis) and severe, life threatening cardiac complications.

Factors contributing to the increase in incidence are primarily an increase in high-risk sexual behaviors. Increased focus on prevention and screening is crucial to prevent long-term complications.  Patients should be advised to use condoms and those in high risk groups should undergo annual screening. It is also important to provide patients in high risk groups with education on signs and symptoms of syphilis as it specifically pertains to their population.

Read more:

Harrison's Principles of Internal Medicine, 20e: Chapter 177: Syphilis

Centers for Disease Control and Prevention: Syphilis

European Centre for Disease Prevention and Control