## **Core Concept**
Anterior uveitis, also known as iridocyclitis, is inflammation of the uveal tract's anterior segment, which includes the iris and ciliary body. It can be associated with various systemic conditions, including autoimmune diseases and infections. Investigations for anterior uveitis aim to identify underlying causes.

## **Why the Correct Answer is Right**
The correct approach to investigating anterior uveitis in a young boy involves considering autoimmune and infectious etiologies. **HLA B27** is associated with seronegative spondyloarthropathies like ankylosing spondylitis, which can cause anterior uveitis. **X-ray sacroiliac joint** is relevant because these conditions often affect the sacroiliac joints. **TORCH agents** (Toxoplasmosis, Rubella, Cytomegalovirus, and Herpes simplex) are infections that can cause uveitis.

## **Why Each Wrong Option is Incorrect**
- **Option D: ELISA for HIV** - While HIV can cause uveitis, it's not a first-line investigation for anterior uveitis in a young boy without other risk factors or symptoms suggestive of HIV infection.
- **Option E: USG abdomen** - This might be useful in certain systemic conditions but is not a primary investigation for anterior uveitis.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that **HLA-B27 associated uveitis** is often linked with **acute anterior uveitis** and can be a presenting feature of **seronegative spondyloarthropathies**. Young adults with recurrent anterior uveitis should be screened for these conditions.

## **Correct Answer: B. a, b, c**