Treponema pallidum / Syphilis

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

Differential

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