O'Byrne Patrick, MacPherson Paul. Syphilis BMJ 2019; 365 :l4159

What you need to know

Incidence rate of syphilis have increased substantially around the world, mostly affecting men who have sex with men and people infected with HIV
Have a low index of suspicion for syphilis in any sexually active patient with genital lesions or rashes
Primary syphilis classically presents as a single, painless, indurated genital ulcer (chancre), but this presentation is only 31% sensitive; lesions can be painful, multiple, and extra-genital
Diagnosis is usually based on serology, using a combination of treponemal and non-treponemal tests. Syphilis remains sensitive to benzathine penicillin G
Staging syphilis is important because it is the basis of management (treatment, expected treatment response, follow-up periods, and partner follow-up)
Patients with syphilis should be screened for HIV, gonorrhoea, and chlamydia

Caused by the bacteria Treponema pallidum, syphilis is transmitted through direct (usually sexual) contact with infected mucosal lesions. Other bodily fluids are also infectious when patients are bacteraemic. With infectivity up to 10-30% per sexual contact or 60% per relationship, syphilis rates have risen 300% since 2000 in many Western countries. While most infections involve men who have sex with men, infections among people with opposite sex partners also occur. In addition to increasing rates, syphilis can cause early complications such as irreversible loss of vision, so awareness of the infection is important for primary care clinicians.