Question
A young adult male came to skin O.P with complaints of painless indurated ulcer on the penis. He gives history of unprotected sex with multiple partners. What is your provisional diagnosis. Name the causative agent Describe in detail the pathogenesis of this disease How do you confirm the diagnosis in the laboratory How do you treat the patient What are the complications of this condition (2+2+3+1+2)
Answer
Provisional diagnosis and causative agent: Primary syphilis — a painless, indurated genital ulcer (chancre) with a history of unprotected sex with multiple partners is classical. Causative agent: Treponema pallidum subspecies pallidum.
Pathogenesis The organism enters through breaches in genital skin/mucosa during sexual contact, multiplies locally, and disseminates via lymphatics and blood early in infection. Disease progresses through stages: Primary syphilis — the painless indurated chancre at the inoculation site, appearing ~3 weeks after exposure, with regional non-tender lymphadenopathy, healing spontaneously. Secondary syphilis — weeks to months later, due to haematogenous spread; generalized rash (including palms/soles), mucous patches, condylomata lata, generalized lymphadenopathy, reflecting an immune-complex-mediated vasculitis. Latent syphilis — asymptomatic seropositive stage. Tertiary syphilis — years later; gummas, cardiovascular syphilis (aortitis, aneurysm), and neurosyphilis (tabes dorsalis, general paresis), driven by a delayed-type hypersensitivity/obliterative endarteritis response to the few remaining organisms.
Laboratory confirmation
- Direct demonstration (from chancre exudate): dark-field microscopy for motile spirochetes; direct fluorescent antibody test (DFA-TP).
- Non-treponemal serology: VDRL/RPR — detect reagin antibody against cardiolipin antigen; used for screening and monitoring treatment response, but can give biological false positives.
- Treponemal serology: TPHA, FTA-ABS, treponemal ELISA — specific, remain positive for life, not useful for monitoring cure.
- PCR on lesion exudate where dark-field is unavailable.
Treatment A single dose of intramuscular benzathine penicillin G is the treatment of choice for primary syphilis (longer course for later-stage disease); doxycycline as an alternative in penicillin-allergic patients (with desensitization preferred in pregnancy, since penicillin remains essential to prevent congenital syphilis); treatment of sexual partners.
Complications Progression to secondary/tertiary syphilis if untreated (cardiovascular syphilis, neurosyphilis, gummas); congenital syphilis if transmitted transplacentally during pregnancy; a Jarisch-Herxheimer reaction (acute febrile reaction from rapid spirochete lysis after starting treatment) can occur.