STI Differential Diagnosis

When considering a differential diagnosis for a sexually transmitted infection (STI), it's crucial to approach the diagnosis systematically, considering the patient's symptoms, sexual history, and physical examination findings. Here's a structured approach:

• Single Most Likely Diagnosis
  • Chlamydia: This is often the most common STI and can present with symptoms such as dysuria, discharge, or can be asymptomatic. Its high prevalence and the fact that it can lead to serious complications like pelvic inflammatory disease (PID) if untreated make it a top consideration.
• Other Likely Diagnoses
  • Gonorrhea: Similar to chlamydia, gonorrhea is a common STI that can cause symptoms like discharge and dysuria. It's also known for its potential to cause severe complications if not treated promptly.
  • Syphilis: With its diverse range of symptoms depending on the stage (primary, secondary, latent, tertiary), syphilis is an important consideration, especially given its potential for severe long-term consequences and the fact that it can be transmitted to newborns.
  • Herpes Simplex Virus (HSV): Characterized by painful genital ulcers, HSV is a common STI that can have significant psychological and physical impacts on patients.
• Do Not Miss Diagnoses
  • HIV: Although not as immediately symptomatic as other STIs, HIV is critical to diagnose early due to its severe long-term consequences and the importance of early antiretroviral therapy initiation.
  • Human Papillomavirus (HPV): While often asymptomatic, certain strains of HPV can lead to cervical cancer, making it essential for diagnosis and management, particularly in preventing long-term complications.
• Rare Diagnoses
  • Lymphogranuloma Venereum (LGV): A less common STI caused by specific serovars of Chlamydia trachomatis, LGV can cause significant morbidity, including proctitis and lymphadenopathy.
  • Granuloma Inguinale (Donovanosis): Characterized by genital ulcers, this STI is rare in many parts of the world but can be seen in certain geographic areas or among specific populations.

Each of these diagnoses requires careful consideration based on the patient's presentation, risk factors, and epidemiological context. A thorough sexual history, physical examination, and appropriate laboratory testing are essential for making an accurate diagnosis and providing effective treatment.