Treponoma pallidum (Syphilis)

What is syphilis?

Syphilis is a bacterial STI caused by the spiral bacterium Treponema pallidum. It progresses through multiple stages and untreated can cause severe systemic damage.

Stages of syphilis

• Primary syphilis — painless chancre at entry site, resolves spontaneously in 3-6 weeks
• Secondary syphilis — palm and sole rash, mucosal lesions, fever, lymphadenopathy
• Latent syphilis — no symptoms but serologically positive; early (<1yr) or late (>1yr)
• Tertiary syphilis — gummas, cardiovascular and neurological complications

Congenital syphilis

• Early congenital — hepatosplenomegaly, rash, nasal discharge, osteochondritis
• Late congenital — Hutchinson's teeth, keratitis, deafness
• Stillbirth — untreated syphilis decreases live birth rates

Diagnostics

• RPR/VDRL — non-treponemal screening tests
• TPHA/FTA-ABS — treponemal confirmatory tests
• Dark field microscopy — direct spirochete visualization from chancre

Treatment

Syphilis is effectively treated with penicillin G (benzathine penicillin injection). Early syphilis requires one dose, late requires multiple. Partner treatment and serological follow-up are mandatory.