**Question:** The most common systemic association of scleritis is –

A. Behçet's disease
B. Vogt-Koyanagi-Harada disease
C. Systemic lupus erythematosus (SLE)
D. Rheumatoid arthritis

**Core Concept:**
Scleritis is an inflammation of the white sclera (tissue) of the eye, which presents as eye pain, redness, and photophobia. Systemic associations indicate underlying systemic diseases that can present with ocular manifestations.

**Why the Correct Answer is Right:**
Scleritis can be associated with various systemic diseases. Among the given options, the correct answer is C. Systemic lupus erythematosus (SLE) is a chronic inflammatory disease that can involve various organs, including the eye. SLE can present with ocular manifestations like scleritis due to the systemic inflammation affecting the blood vessels in the sclera.

**Why Each Wrong Option is Incorrect:**
A. Behçet's disease: Although Behçet's disease can present with ocular manifestations like scleritis, it is less commonly associated with scleritis compared to SLE.
B. Vogt-Koyanagi-Harada disease is a disorder affecting melanocytes and is more likely to present with uveitis (inflammation of the uvea), rather than scleritis.
D. Rheumatoid arthritis (RA) typically presents with ocular manifestations like episcleritis (inflammation limited to the episclera) rather than scleritis.

**Clinical Pearl:**
Scleritis can be a valuable clue for identifying underlying systemic diseases like SLE. A thorough history and examination are essential in differentiating between episcleritis and scleritis, as they have distinct clinical features and require different management strategies. Early identification and management of these associated systemic diseases help prevent severe ocular complications and improve patient outcomes.