Dermatology, Venereology and Leprosy
Sexually Transmitted Infections
STIs for MBBS and NEET-PG: syphilis stages and chancre, VDRL and TPHA, chancroid, LGV, donovanosis, penicillin treatment and the syndromic approach, mapped to NMC codes DR10.
MedNext Academy | 3 min read
Sexually Transmitted Infections
STIs for MBBS and NEET-PG: syphilis stages and chancre, VDRL and TPHA, chancroid, LGV, donovanosis, penicillin treatment and the syndromic approach, mapped to NMC codes DR10.
This chapter covers the sexually transmitted infections, with syphilis at its centre, from the painless primary chancre through the palm-and-sole rash of secondary disease to congenital syphilis. It also details the non-syphilitic genital ulcers, the serological tests, penicillin treatment, the syndromic approach and the counselling that surrounds every diagnosis.
High-yield: Sexually Transmitted Infections
- Syphilis is caused by the spirochaete Treponema pallidum and is divided into primary, secondary, latent and tertiary stages.
- The primary chancre is a single painless indurated ulcer with a clean base that appears at the site of inoculation and heals spontaneously.
- Secondary syphilis presents weeks later with a widespread symmetrical rash that classically involves the palms and soles, and with mucous patches and condylomata lata.
- The organism is seen by dark-ground microscopy of exudate from an early lesion, as it cannot be cultured on ordinary media.
- Non-treponemal tests such as the VDRL and RPR are used for screening and to monitor treatment response, while treponemal tests such as TPHA confirm the diagnosis.
- The VDRL can give a biological false positive in pregnancy, autoimmune disease and other infections.
- Benzathine penicillin is the treatment of choice for syphilis at all stages, with doxycycline as an alternative in penicillin allergy.
- A Jarisch-Herxheimer reaction, a self-limiting febrile flare, may follow the first dose of treatment as organisms are killed.
- Congenital syphilis is prevented by antenatal screening and treating the mother, and features include a saddle nose, Hutchinson's teeth and interstitial keratitis.
- Chancroid, caused by Haemophilus ducreyi, produces multiple painful ulcers with ragged undermined edges and tender suppurative lymph nodes.
- Lymphogranuloma venereum, caused by Chlamydia trachomatis, causes a transient ulcer followed by the groove sign of enlarged inguinal nodes.
- Donovanosis (granuloma inguinale), caused by Klebsiella granulomatis, gives beefy-red painless ulcers that bleed easily, with Donovan bodies on tissue smear.
- The syndromic approach manages genital ulcer and discharge syndromes empirically to cover the likely organisms without waiting for laboratory results.
- Every patient with a sexually transmitted infection should be counselled non-judgementally, offered partner notification and screened for HIV and other coinfections.
Genital ulcer differentials
- **Syphilis:** Single painless indurated chancre, clean base. Treponema pallidum, dark-ground.
- **Chancroid:** Multiple painful ulcers, ragged edges, tender nodes. Haemophilus ducreyi.
- **LGV:** Transient ulcer then groove sign nodes. Chlamydia trachomatis.
- **Donovanosis:** Beefy-red painless bleeding ulcer, Donovan bodies. Klebsiella granulomatis.
NMC competencies in this chapter
- **DR10.1:** Identifying and classifying syphilis by presentation and clinical stage
- **DR10.2:** Identifying the spirochaete on dark-ground microscopy
- **DR10.3:** Pharmacology of drugs used to treat syphilis
- **DR10.4:** Prevention of congenital syphilis
- **DR10.5:** Non-judgemental counselling of patients with sexually transmitted infections
- **DR10.6:** Aetiology and clinical features of non-syphilitic sexually transmitted diseases
- **DR10.7:** Differentiating non-syphilitic sexually transmitted ulcers by clinical features
- **DR10.8:** Pharmacology of drugs used for non-syphilitic sexually transmitted diseases
- **DR10.9:** Syndromic approach to ulcerative sexually transmitted disease
- **DR10.10:** Aetiology, diagnosis and features of urethral and vaginal discharge syndromes
- **DR10.11:** Aetiology, diagnosis and management of genital wart and other STI syndromes
Frequently Asked Questions
What does the primary chancre of syphilis look like?
A single, painless, indurated ulcer with a clean base at the site of inoculation, appearing a few weeks after exposure and healing on its own even without treatment.
How is syphilis diagnosed serologically?
Non-treponemal tests such as VDRL and RPR are used for screening and to monitor treatment, while treponemal tests such as TPHA confirm the diagnosis. Early lesions can also be examined by dark-ground microscopy.
What is the treatment of choice for syphilis?
Benzathine penicillin at all stages, with doxycycline as an alternative in penicillin allergy. A self-limiting febrile Jarisch-Herxheimer reaction may follow the first dose.
What is the syndromic approach?
It manages genital ulcer or discharge syndromes with empirical treatment covering the likely organisms, so that patients are treated at first contact without waiting for laboratory confirmation.
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