Causes of Unilateral Episcleritis
Most cases of unilateral episcleritis are idiopathic, but when associated with systemic disease, inflammatory bowel disease (particularly ulcerative colitis and Crohn's disease) and rheumatoid arthritis are the most common underlying conditions. 1, 2
Idiopathic Disease
- The majority of episcleritis cases have no identifiable underlying cause, occurring as isolated ocular inflammation without systemic disease association 3
- Idiopathic episcleritis is more common in women and typically affects those between 40-50 years of age 3
Inflammatory Bowel Disease
- Episcleritis is one of the most common ocular manifestations of IBD, with reported incidence ranging from 4-12% of IBD patients (though these are likely overestimates from tertiary centers) 1
- Episcleritis in IBD typically correlates with bowel disease activity, unlike uveitis which can occur independently of intestinal symptoms 1
- The condition affects both ulcerative colitis and Crohn's disease patients, presenting with hyperemic sclera and conjunctiva, itching, and burning sensation 1
Rheumatoid Arthritis
- Rheumatoid arthritis accounts for 8-15% of all scleritis cases and is also associated with episcleritis, though RA patients more commonly develop the more severe diffuse or necrotizing forms of scleritis 2
- Approximately 2% of RA patients will develop scleritis, with episcleritis being a less severe but related manifestation 2
Other Systemic Autoimmune Diseases
- Systemic lupus erythematosus can cause episcleritis, though this is relatively rare and typically occurs in the context of active systemic disease (SLEDAI scores >4) 4
- Other rheumatologic conditions including granulomatosis with polyangiitis may be associated with episcleritis, though these more commonly cause scleritis 5, 6
Clinical Distinction from Scleritis
The key distinguishing feature is that episcleritis presents with mild or no pain, hyperemia of superficial vessels, and no visual changes, whereas scleritis causes severe pain, deep vessel involvement, and potential vision loss. 1, 7, 8
- Episcleritis is relatively painless with simple redness, itching, and burning 1, 3
- The absence of moderate-to-severe eye pain, photophobia, blurred vision, and diminished visual acuity differentiates episcleritis from the more serious conditions of scleritis and uveitis 1, 8
When to Investigate for Systemic Disease
- If episcleritis is recurrent, bilateral, or associated with other systemic symptoms, workup for underlying rheumatologic disease is warranted 3, 6
- Blood work including inflammatory markers, rheumatoid factor, anti-CCP antibodies, and ANA may be helpful in identifying associated systemic disease 3, 6
- Up to 50% of patients with scleritis or episcleritis have an associated systemic disease, making systemic evaluation important in appropriate clinical contexts 6