Differential Diagnosis for Painful Oral Sores

The patient presents with painful sores on the lips and inside the mouth, accompanied by concerns about sexually transmitted infections (STIs) due to a recent incident. The physical exam reveals white ulcerations on the bottom lip, two on the top inner lip, and one on the right cheek.

• Single Most Likely Diagnosis
  • Herpes Simplex Virus (HSV) Infection: Given the patient's symptoms of painful sores and the recent stressor of discovering her boyfriend's infidelity, which could have triggered an outbreak, HSV infection is a strong consideration. The presence of white ulcerations is consistent with oral herpes (HSV-1), which can be spread through oral contact.
• Other Likely Diagnoses
  • Aphthous Ulcers (Canker Sores): These are common, recurrent, and can be triggered by stress, among other factors. Their appearance as painful ulcers inside the mouth aligns with the patient's symptoms.
  • Oral Syphilis (Primary): Given the patient's concern about STIs, primary syphilis, which can manifest as a single, painless chancre but sometimes can be painful, should be considered. However, the presence of multiple lesions makes this less likely.
  • Oral Gonorrhea: This STI can cause oral lesions and should be considered given the patient's concerns, though it is less common than other causes of oral sores.
• Do Not Miss Diagnoses
  • Oral Cancer: Although less likely given the acute presentation, any oral lesion that does not heal within a couple of weeks should raise concern for oral cancer, especially in patients with risk factors like smoking or alcohol use.
  • HIV-Related Oral Lesions: Individuals with HIV can present with a variety of oral lesions, including those caused by opportunistic infections. Given the patient's concern about STIs, testing for HIV and considering HIV-related conditions is crucial.
• Rare Diagnoses
  • Behçet's Disease: A rare condition characterized by recurrent oral ulcers, along with genital ulcers and ocular inflammation. It's less likely but should be considered if the patient has a history of recurrent oral and genital ulcers.
  • Erythema Multiforme: An immune-mediated condition that can cause oral and skin lesions, often in response to infections like HSV or medications. It's a rare consideration but important in patients with severe or recurrent episodes of oral ulcers.

Each diagnosis should be considered in the context of the patient's full history, physical examination, and laboratory testing, including STI screening as requested by the patient.