Sign in Subscribe
Education

Common Sexually Transmitted Infections (STI)

mLpenguin

• 2 min read
Common Sexually Transmitted Infections (STI)
Photo by National Cancer Institute / Unsplash

Herpes Simplex Virus (Genital Herpes)

HSV-2 (most common), HSV-1 also possible

  • Presentation:
    • Painful grouped vesicles on erythematous base (genital, perianal)
    • Ulcerations after vesicle rupture
    • Systemic symptoms: fever, malaise, lymphadenopathy
      • Tender inguinal nodes
    • Recurrent outbreaks common
  • Diagnosis: PCR or viral culture of lesions
  • Treatment:
    • Acyclovir, valacyclovir, famciclovir
    • No cure; suppressive therapy reduces outbreaks/transmission

Human Papillomavirus (HPV)

HPV types 6, 11 (warts), 16, 18 (cancer)

  • Presentation:
    • Genital warts: soft, flesh-colored, cauliflower-like lesions (mostly HPV types 6,11)
    • High-risk types (16,18) → cervical dysplasia/cancer (no lesions)
  • Diagnosis: Clinical; Pap smear & HPV DNA testing for high-risk types
  • Treatment:
    • Warts: topical podophyllin, imiquimod, cryotherapy, surgical removal
    • Cervical dysplasia: monitored or treated with excision
  • Prevention: HPV vaccine (Gardasil)

Syphilis

Treponema pallidum (spirochete)

  • Presentation:
    • Primary: painless chancre (ulcer with clean base, indurated edges)
      • Painless inguinal nodes
    • Secondary: maculopapular rash (palms/soles), condyloma lata (broad, moist genital warts), systemic symptoms
      • Generalized lymphadenopathy
    • Tertiary: gummas, aortitis, neurosyphilis
  • Diagnosis: RPR/VDRL screening, confirm with FTA-ABS
  • Treatment:
    • Penicillin G benzathine IM (single dose for primary/secondary)
    • Neurosyphilis: IV penicillin G

Chlamydia trachomatis

Chlamydia trachomatis (serovars D–K)

  • Presentation:
    • Often asymptomatic
    • Urethritis: dysuria, mucoid (watery) discharge
    • Cervicitis: mucopurulent discharge, friable cervix
    • PID, infertility if untreated
  • Diagnosis: NAAT (nucleic acid amplification test)
  • Treatment:
    • Azithromycin
    • Doxycycline
    • Plus treatment for gonorrhoeae (if not excluded)

Lymphogranuloma Venereum (LGV)

Chlamydia trachomatis, serovars L1, L2, L3, intracellular gram-negative bacterium

  • Presentation:
    • Primary stage (Days 3–30 post-exposure):
      • Often starts with asymptomatic ulcer
      • Small, transient painless genital ulcer or papule
      • Often goes unnoticed (heals on its own)
    • Secondary stage (2–6 weeks later):
      • Painful inguinal or femoral lymphadenopathy ("buboes")
      • May become fluctuant and rupture
      • Groove sign: Inguinal ligament separates two matted groups of nodes
      • May have constitutional symptoms: fever, malaise, myalgia
    • Late stage (tertiary):
      • Chronic inflammation can cause rectal strictures, fistulas, genital elephantiasis (especially in MSM)
  • Treatment:
    • Doxycycline (first-line)
      • Erythromycin
    • Aspiration or drainage of buboes may be needed if fluctuant

Neisseria gonorrhoeae

Neisseria gonorrhoeae

  • Presentation:
    • Urethritis: purulent discharge, dysuria
    • Cervicitis, PID, epididymitis
    • Disseminated gonococcal infection (arthritis (knee most common), tenosynovitis, dermatitis - rash with few pustules)
  • Diagnosis: NAAT, culture
  • Treatment:
    • Ceftriaxone IM
    • Plus treatment for chlamydia (if not excluded)

Trichomonas vaginalis

Trichomonas vaginalis (protozoan)

  • Presentation:
    • Vaginitis: frothy yellow-green discharge, foul odor, vaginal itching, erythema of vaginal mucosa (strawberry cervix)
  • Diagnosis: Wet mount microscopy (motile trichomonads), NAAT
  • Treatment:
    • Metronidazole

Bacterial Vaginosis

Overgrowth of anaerobic bacteria, especially Gardnerella vaginalis, replacing normal lactobacilli in the vaginal flora.

  • Presentation:
    • Thin, gray-white vaginal discharge, fishy odor (esp. after intercourse)
    • Usually no inflammation
  • Diagnosis: Amsel criteria
    • Thin, white discharge
    • Clue cells on wet mount
    • pH > 4.5
    • Positive whiff test (KOH + discharge → fishy odor)
  • Treatment:
    • Metronidazole (pill or gel)

Haemophilus ducreyi (Chancroid)

Haemophilus ducreyi, a Gram-negative coccobacillus

  • Presentation:
    • Painful genital ulcers with ragged edges
    • Tender inguinal lymphadenopathy (buboes)
  • Diagnosis: Clinical, PCR if available
  • Treatment:
    • Azithromycin
    • Ceftriaxone

HIV

Human Immunodeficiency Virus

  • Presentation:
    • Acute retroviral syndrome: flu-like illness, rash, lymphadenopathy
  • Symptoms:
    • Fever, sore throat, myalgias
  • Treatment:
    • ART (Antiretroviral therapy): integrase inhibitor-based regimen
    • Lifelong treatment; regular monitoring of viral load and CD4
  • Painful ulcers with painful lymph nodes → Think chancroid
  • Painless ulcer with painless lymph nodes → Think primary syphilis
  • Small ulcer followed by painful lymphadenopathy → Think LGV
  • Grouped vesicles with tender nodes → Think HSV
  • Flu-like illness + rash + diffuse nodes → Think secondary syphilis or acute HIV