At a glance
- PrEP starts with confirming HIV-negative status and assessing renal function, HBV status, pregnancy potential, and STI risk.
- Syphilis treatment depends on stage; staging is often the hardest part.
- Do not diagnose neurosyphilis from serum RPR titer alone; neurologic, ocular, or otic symptoms drive evaluation.
- Test at anatomic sites of exposure for gonorrhea and chlamydia.
- Partner treatment, follow-up testing, and public health reporting are part of STI care.
Objectives
- 1.Identify PrEP candidates and baseline safety testing.
- 2.Stage syphilis and select appropriate penicillin-based therapy.
- 3.Interpret RPR trends after treatment.
- 4.Manage common gonorrhea, chlamydia, and trichomonas scenarios.
- 5.Recognize when HIV guidelines or specialist input are needed.
Key concepts
PrEP is prevention plus longitudinal care
PrEP is indicated for patients with ongoing risk for HIV acquisition and requires baseline HIV testing, renal assessment for tenofovir-containing regimens, HBV evaluation, STI screening, and follow-up monitoring. The iPrEx trial established proof of concept for oral TDF/FTC PrEP in MSM, with efficacy strongly linked to adherence.
Self-check
Before starting oral tenofovir/emtricitabine PrEP, which baseline step is essential?
Select one answer to view the rationale and peer response data.
Acute HIV must be excluded when symptoms fit
A negative antibody-only test can miss acute HIV. If recent exposure and viral syndrome are present, use an antigen/antibody test and HIV RNA as appropriate before PrEP or when evaluating possible seroconversion.
Self-check
A patient requesting PrEP reports fever, sore throat, rash, and condomless sex 12 days ago. Rapid antibody test is negative. Best next step?
Select one answer to view the rationale and peer response data.
Syphilis stage determines duration
Primary syphilis presents with chancre, secondary with rash/mucous patches/condyloma lata/systemic symptoms, and latent disease has positive serology without symptoms. Early latent is infection acquired within the prior year; late latent or unknown duration generally needs three weekly benzathine penicillin doses.
Self-check
A patient has positive treponemal test and RPR 1:64 but no symptoms. Last negative syphilis test was 4 months ago. Stage?
Select one answer to view the rationale and peer response data.
Primary, secondary, and early latent syphilis use single-dose benzathine penicillin
For nonpregnant adults without neurosyphilis, ocular syphilis, or otosyphilis, primary, secondary, and early latent syphilis are treated with benzathine penicillin G 2.4 million units IM once. Late latent or unknown duration requires weekly dosing for three weeks.
Self-check
A nonpregnant adult has secondary syphilis with diffuse rash including palms and soles. No neurologic, ocular, or otic symptoms. Best treatment?
Select one answer to view the rationale and peer response data.
RPR follow-up is about fourfold change
Nontreponemal titers are used to follow response. A fourfold change equals two dilutions, such as 1:32 to 1:8. Treponemal tests often stay positive and should not be used as test of cure.
Self-check
Which RPR change represents a fourfold decline after syphilis therapy?
Select one answer to view the rationale and peer response data.
Neurosyphilis evaluation is symptom-driven
CSF evaluation is guided by neurologic findings, cranial nerve dysfunction, meningitis, stroke, altered mental status, ocular disease, or otic symptoms. High serum RPR alone is not an indication for lumbar puncture.
Self-check
Which patient most needs evaluation for neurosyphilis/ocular syphilis?
Select one answer to view the rationale and peer response data.
Gonorrhea requires ceftriaxone and exposure-site testing
Nucleic acid amplification testing should be sent from sites of exposure: urine/urethral, vaginal/cervical, rectal, and pharyngeal as indicated. Current CDC guidance uses ceftriaxone-based therapy for uncomplicated gonorrhea, with chlamydia treatment added if chlamydia has not been excluded.
Self-check
A man has receptive oral and anal sex and urethral symptoms. What testing strategy is best?
Select one answer to view the rationale and peer response data.
Chlamydia treatment depends on site and pregnancy
Doxycycline is preferred for many nonpregnant adolescents and adults with chlamydia, especially rectal infection. Azithromycin remains important in pregnancy and selected situations. Partner management and abstinence until treatment completion are essential.
Self-check
A nonpregnant adult has rectal chlamydia. Preferred therapy?
Select one answer to view the rationale and peer response data.
Trichomonas is often missed if not considered
Trichomoniasis can cause vaginal discharge, irritation, dysuria, or be asymptomatic. Metronidazole-based therapy is used, and partners should be treated to prevent reinfection.
Self-check
A woman has NAAT-confirmed trichomoniasis. What additional management point is most important?
Select one answer to view the rationale and peer response data.
STI care includes prevention, vaccines, and partners
STI visits are opportunities for HIV testing, PrEP discussion, hepatitis B vaccination, HPV vaccination when eligible, pregnancy assessment, partner services, expedited partner therapy where allowed, and counseling without stigma.
Self-check
A patient is treated for gonorrhea. Which prevention step should routinely be considered at the same visit?
Select one answer to view the rationale and peer response data.
Evidence & guidelines
Guidelines
- Sexually Transmitted Infections Treatment Guidelines, 2021CDC. MMWR Recomm Rep. 2021;70(4):1-187. PMID: 34292926. DOI: 10.15585/mmwr.rr7004a1.Primary U.S. reference for syphilis, gonorrhea, chlamydia, trichomoniasis, partner management, and follow-up.
- HIV clinical guidelinesClinicalInfo.HIV.gov, current guideline portal.Current federal HIV guidance, including prevention, testing, ART, pregnancy, and opportunistic infection resources.
Key trials
- Preexposure chemoprophylaxis for HIV prevention in men who have sex with menGrant RM, Lama JR, Anderson PL, et al. N Engl J Med. 2010;363(27):2587-2599. PMID: 21091279. DOI: 10.1056/NEJMoa1011205.Landmark iPrEx trial showing oral TDF/FTC PrEP efficacy linked strongly to adherence.
Pearls
- PearlConfirm HIV-negative status before PrEP.
- PearlStage syphilis before choosing one dose versus three weekly doses.
- PearlRPR follows response; treponemal tests usually do not become negative.
- PearlTest GC/CT at sites of exposure.
Related cases
Ophthalmology
The Fog Behind the Eye
When syphilis moves from the rash to the retina.STI
Soft Edges and a Swollen Groin
A painful genital ulcer that resists easy categorization.Sexually Transmitted Infections
The Great Imitator
A rash that reaches the palms and a genital sore the patient thought had healed.