Snapshot A 35-year-old man presents to the clinic after noticing an ulcer on his penis. He is unsure how long the ulcer has been present, as he has not felt pain in the area. He denies any symptoms of discharge, rash, or dysuria. Sexual history is notable for unprotected sexual intercourse with multiple partners over the past year. On physical examination, there is a 1-cm ulcer on the underside of the penis and bilateral inguinal lymphadenopathy. Dark-field microscopy reveals motile, spiral-shaped organisms. Introduction Classification Treponema pallidum spirochete Epidemiology demographics most common during years of peak sexual activity most new cases in men and women aged 20-29 years recent rise in syphilis cases among MSM community co-infection of syphilis with HIV is high location genitourinary tract risk factors unprotected sex IV drug use and needle-sharing Pathogenesis mechanism T. pallidum rapidly penetrates intact mucus membranes or dermal abrasions and enters the lymphatics and blood to cause systemic infection transmission intimate contact with infectious lesions (most common) blood transfusion transplacentally from infected mother to fetus Associated conditions cardiovascular syphilis aneurysm formation neurosyphilis Prognosis favorable prognosis for patients diagnosed with either primary or secondary syphilis 20% of untreated patients with tertiary syphilis die of the disease prognosis for tertiary syphilis depends on extent of scarring and tissue damage with adequate treatment, 90% of patients with neurosyphilis have a favorable clinical recovery Presentation Primary syphilis painless chancre indurated edge can visualize treponemes in fluid from chancre using dark-field microscopy Secondary syphilis disseminated disease diffuse, maculopapular rash that involves the palms and soles condylomata lata smooth, painless, wart-like white lesions on genitals lymphadenopathy patchy alopecia Tertiary syphilis gummas chronic granulomas aortitis from destruction of the vasa vasorum neurosyphilis tabes dorsalis Affects spinal dorsal column and dorsal root ganglia resulting in loss of proprioception and vibratory sensation below the level of the lesion Argyll Robertson pupil pupil constricts with accommodation but is not reactive to light other symptoms broad-based ataxia positive Romberg stroke without hypertension Congenital syphilis facial abnormalities rhagades (linear scars at angle of mouth) nasal discharge saddle nose notched Hutchinson teeth mulberry molars short maxilla saber shins sensorineural deafness Studies Labs Nonspecific serologic testing VDRL (Venereal Disease Research Laboratory) RPR (rapid plasma reagent) Specific serologic testing FTA-ABS (fluorescent treponemal antibody-absorption) use to confirm diagnosis Microscopy dark-field microscopy visualize motile spirochetes Treponema Pallidum Labs VDRL FTA Interpretation + + Active infection + - Probably false positive - + Successfully treated Differential Herpes simplex virus painful genital vesicles and ulcers Haemophilus ducreyi painful genital ulcer with exudate Lymphogranuloma venereum buboes Klebsiella granulomatis beefy red ulcer that bleeds on contact Treatment Medical penicillin IM penicillin for primary or secondary syphilis and early latent syphilis IV penicillin G for late latent syphilis doxycycline an alternative for treating early and late latent syphilis Complications Jarisch-Herxheimer reaction flu-like syndrome after starting treatment for syphilis due to toxins released by killed T. pallidum complications of tertiary syphilis aortic insufficiency tabes dorsalis general paresis