Differential Diagnosis for 34-year-old Female with Bilateral Conjunctivitis, Photophobia, and Mouth Sores

• Single Most Likely Diagnosis
  • Viral conjunctivitis (e.g., adenoviral conjunctivitis): This is likely due to the combination of bilateral conjunctivitis, photophobia, and the presence of mouth sores, which could be indicative of a viral infection such as herpangina or hand, foot, and mouth disease, although the latter is more common in children.
• Other Likely Diagnoses
  • Herpes simplex virus (HSV) infection: HSV can cause conjunctivitis and oral lesions (cold sores), fitting the patient's symptoms.
  • Stevens-Johnson Syndrome (SJS): Although less common, SJS is a severe condition that can present with conjunctivitis, photophobia, and mucous membrane lesions, including mouth sores. The absence of fever does not rule out SJS.
  • Allergic conjunctivitis: This could be considered if the patient has a history of allergies, but the presence of mouth sores makes it less likely.
• Do Not Miss Diagnoses
  • Gonococcal conjunctivitis: This is a serious condition that requires prompt treatment to prevent vision loss. It can present with severe conjunctivitis and is a critical diagnosis not to miss, despite its lower likelihood.
  • Sarcoidosis: Although rare, sarcoidosis can cause uveitis and conjunctivitis, along with other systemic symptoms. It's a diagnosis that could be considered, especially if other systemic symptoms are present.
• Rare Diagnoses
  • Behçet's disease: A rare condition characterized by recurrent oral ulcers, genital ulcers, and uveitis, among other symptoms. It's less likely but could be considered if the patient has a history of recurrent oral ulcers and other systemic symptoms.
  • Reactive arthritis (Reiter's syndrome): This condition can follow a bacterial infection and is characterized by arthritis, urethritis, and conjunctivitis. It's less common and typically follows a gastrointestinal or urinary tract infection.