• Clinical science

Sexually transmitted infections


The term "sexually transmitted infections" (STIs) refers to a group of infections that are mainly transmitted via sexual intercourse. The most common symptoms of STIs are pain in the suprapubic and genital area, urethral or vaginal discharge, and genital lesions, which may or may not be painful. Some STIs (e.g., HPV) may induce or predispose to malignant changes. The majority of STIs are asymptomatic, and therefore easily spread. If a patient is already infected with an STI, they are predisposed to coinfections with further STIs. There are various treatment options for each STI, with simultaneous treatment of the partner often necessary to prevent recurrent infections. In some cases, health care providers are required by law to report cases of STIs to county and health state departments (e.g., HIV, hepatitis B).

Overview of sexually transmitted infections

Pathogens Localized disease Management
Viral Human papillomavirus (HPV)
  • Local cytotoxic therapy (e.g., with 5-fluorouracil)
  • Cryotherapy
  • Operative management: curettage (surgical excision), laser surgery, or electrosurgery

Herpes simplex virus type 2 (HSV-2)

  • Acyclovir PO for episodic or suppressive treatment
  • None
Hepatitis B
  • None
  • Systemic antiviral therapy PO (e.g., entecavir)
  • Interferon (immune modulating, antiviral, and antiproliferative agent) injected SC or IM
Bacterial Chlamydia trachomatis D-K
Chlamydia trachomatis L1-L3
Klebsiella granulomatis
Haemophilus ducreyi
Neisseria gonorrhea
Treponema pallidum
Fungal Candida albicans
Parasitic Trichomonas vaginalis
Phthirus pubis


Genital lesions

Pathogen Clinical features Diagnosis
Painless lesions Human papillomavirus
  • Condylomata acuminata
    • Single or multiple skin-colored papular eruptions (1–5mm) ; smooth or verrucous
    • Usually painless
    • Located on internal and external genitalia
  • Bowenoid papulosis
    • Single or multiple small papules (may coalesce into larger plaques)
    • Pigmented, with a flat-to-verrucous surface
    • Most commonly on the penis shaft or external female genitals
  • Clinical exam and biopsy
Klebsiella granulomatis
  • Granuloma inguinale
    • Large (5–10 mm), beefy-red, expanding suppurative ulcers ;
    • Painless; bleed easily
    • Often malodorous because of bacterial coinfection
    • Commonly located in skin folds
Chlamydia trachomatis L1-L3
Treponema pallidum
  • Chancre
    • Singular red, round, and raised painless ulcer with elevated edges
    • Heals spontaneously within 4–8 weeks
    • Manifests mainly on the glans penis, or vulva and cervix
    • Possibly concurrent regional adenopathy
  • Condylomata lata
    • Painless, warty erosions on the genitals in the secondary phase of syphilis that are velvety, moist, and broad-based
    • Resolve spontaneously after weeks to months
Painful lesions Herpes simplex virus type 1 and 2 (mostly HSV-2)
Haemophilus ducreyi
  • Clinical exam and culture