USMLE Guide: Sexually Transmitted Infections

Introduction

Sexually Transmitted Infections (STIs) are a group of infections transmitted through sexual contact. They can be caused by bacteria, viruses, parasites, or fungi. Understanding the pathogenesis, clinical presentation, diagnosis, and management of STIs is crucial for medical professionals. This USMLE guide aims to provide a concise overview of the key concepts related to STIs.

Key Topics:

1. Chlamydia trachomatis

   • Epidemiology: Most commonly reported bacterial STI in the United States
   • Clinical presentation: Often asymptomatic, but may cause urethritis, cervicitis, or pelvic inflammatory disease (PID)
   • Diagnosis: Nucleic acid amplification tests (NAATs) are the most sensitive.
   • Treatment: Azithromycin or doxycycline as first-line therapy

2. Neisseria gonorrhoeae

   • Epidemiology: Second most commonly reported bacterial STI in the United States
   • Clinical presentation: Can cause urethritis, cervicitis, proctitis, or pharyngitis; disseminated gonococcal infection (DGI) can occur
   • Diagnosis: NAATs are the preferred method.
   • Treatment: Dual therapy with ceftriaxone and azithromycin

3. Syphilis

   • Epidemiology: Incidence has been increasing in recent years
   • Clinical presentation: Divided into primary, secondary, latent, and tertiary stages; can affect almost any organ system if untreated
   • Diagnosis: Serologic tests (e.g., non-treponemal tests followed by confirmatory treponemal tests)
   • Treatment: Penicillin G is the treatment of choice

4. Human papillomavirus (HPV)

   • Epidemiology: Most common viral STI in the United States
   • Clinical presentation: Can cause genital warts or various types of cancer (e.g., cervical, anal, oropharyngeal)
   • Diagnosis: Visual inspection, HPV DNA testing, or Pap smear
   • Treatment: No specific antiviral therapy; management focuses on removing or treating lesions

5. Herpes simplex virus (HSV)

   • Epidemiology: HSV-2 is more commonly associated with genital infections
   • Clinical presentation: Primary infection presents with painful genital ulcers; recurrent infections are typically milder
   • Diagnosis: Viral culture, PCR, or serologic testing for antibodies
   • Treatment: Antiviral therapy with acyclovir, valacyclovir, or famciclovir

6. HIV/AIDS

   • Epidemiology: Global pandemic; transmission primarily through sexual contact, blood exposure, or perinatal transmission
   • Clinical presentation: Acute retroviral syndrome followed by varying stages of HIV infection; opportunistic infections and malignancies in advanced disease
   • Diagnosis: Combination immunoassay followed by confirmatory tests (e.g., Western blot)
   • Treatment: Antiretroviral therapy (ART) for all HIV-infected individuals

Conclusion

Understanding the key concepts related to Sexually Transmitted Infections is crucial for medical professionals. This USMLE guide provides an overview of the epidemiology, clinical presentation, diagnosis, and treatment of common STIs, including Chlamydia trachomatis, Neisseria gonorrhoeae, syphilis, human papillomavirus (HPV), herpes simplex virus (HSV), and HIV/AIDS.