Differential Diagnosis for Painful Sores on the Lips and in the Mouth

The patient's symptoms of painful sores on the top and bottom lip and in her mouth and gums, combined with her recent concern about sexually transmitted infections (STIs) due to her boyfriend's infidelity, suggest several potential diagnoses. These can be categorized as follows:

• Single Most Likely Diagnosis

  • Herpes Simplex Virus (HSV) Infection: This is a common cause of painful oral and genital sores. Given the patient's concern about STIs and the nature of her symptoms, HSV infection is a highly plausible diagnosis. The stress of discovering her boyfriend's infidelity could also trigger an outbreak.

• Other Likely Diagnoses

  • Aphthous Ulcers (Canker Sores): These are common, recurrent, and can be triggered by stress, among other factors. The patient's recent emotional distress could contribute to the development of aphthous ulcers.
  • Syphilis (Primary): This STI can cause oral sores, and given the patient's concern about STIs, it should be considered, especially if she has not been tested recently.
  • Gingivitis or Periodontal Disease: While not typically presenting with acute sores, severe gum disease can cause painful gums and could be exacerbated by poor oral hygiene or other factors.

• Do Not Miss Diagnoses

  • HIV Infection: Oral ulcers can be a symptom of acute HIV infection. Given the patient's concern about STIs, testing for HIV is crucial.
  • Gonorrhea or Chlamydia: These STIs can cause oral infections if transmitted through oral sex. Although less common, they are important to consider and rule out.
  • Lymphogranuloma Venereum (LGV): A less common STI that can cause oral ulcers, LGV is important to consider, especially if the patient has engaged in high-risk sexual behaviors.

• Rare Diagnoses

  • Behçet's Disease: A rare condition characterized by recurrent oral ulcers, among other symptoms. It's less likely but should be considered if other diagnoses are ruled out and the patient has a history of recurrent oral ulcers.
  • Erythema Multiforme: A skin condition that can cause oral sores, often triggered by infections or medications. It's less common and would typically be associated with other skin manifestations.

Each of these diagnoses should be considered in the context of the patient's full medical history, sexual history, and the results of physical examination and diagnostic tests.