Differential Diagnosis for Episcleritis and Herpes Ophthalmicum

When differentiating between episcleritis and herpes ophthalmicum, it's crucial to consider various diagnoses based on their likelihood and potential impact on patient health. The following categories help organize the thought process:

• Single Most Likely Diagnosis
  • Episcleritis: This is often the first consideration due to its relatively common presentation of sectoral or diffuse inflammation of the episclera, which is a thin layer on top of the sclera. It can be associated with systemic autoimmune disorders but also occurs independently.
• Other Likely Diagnoses
  • Herpes Zoster Ophthalmicus (HZO): This condition, caused by the reactivation of varicella-zoster virus in the trigeminal nerve ganglion, presents with a painful vesicular rash in a dermatomal distribution, often involving the ophthalmic division (V1). It can lead to serious ocular complications.
  • Scleritis: Although less common than episcleritis, scleritis is a significant inflammatory disease of the sclera that can cause severe pain, redness, and vision loss. It often requires aggressive treatment.
• Do Not Miss Diagnoses
  • Acute Angle-Closure Glaucoma: This is an ocular emergency characterized by sudden increased intraocular pressure, which can cause severe eye pain, redness, and vision loss. It requires immediate medical attention to prevent permanent vision loss.
  • Orbital Cellulitis: An infection of the orbital tissues posterior to the orbital septum, which can lead to severe complications, including vision loss and intracranial involvement, if not promptly treated.
• Rare Diagnoses
  • Polyarteritis Nodosa (PAN): A systemic vasculitis that can affect various organs, including the eyes, presenting with episcleritis or scleritis among other symptoms.
  • Relentless Plasminogen Activator (RPA) or other autoimmune conditions: Though rare, these conditions can mimic episcleritis or scleritis and require specific diagnostic tests and treatments.

Each diagnosis has distinct clinical features, and a thorough history, physical examination, and sometimes additional diagnostic tests are necessary to differentiate between them accurately. The key to successful management lies in early recognition and appropriate treatment to prevent long-term complications.