**Core Concept**
Chronic uveitis in a 10-year-old boy suggests an underlying systemic or autoimmune condition that requires a thorough diagnostic evaluation. The investigation of choice should aim to identify the underlying cause of uveitis, which may involve a combination of laboratory tests and imaging studies.

**Why the Correct Answer is Right**
The correct investigation for chronic uveitis in a child is the **Antinuclear Antibody (ANA) test**. This test detects the presence of autoantibodies against nuclear antigens, which are commonly associated with autoimmune diseases such as juvenile idiopathic arthritis (JIA) and systemic lupus erythematosus (SLE). These conditions are known to cause chronic uveitis in children. The ANA test is a useful screening tool to identify children at risk of developing autoimmune diseases.

**Why Each Wrong Option is Incorrect**
**Option A:** HLA-B27 typing is more specific for ankylosing spondylitis and reactive arthritis, which are less common causes of chronic uveitis in children.

**Option B:** ESR (Erythrocyte Sedimentation Rate) is a non-specific marker of inflammation and is not specific for the diagnosis of chronic uveitis.

**Option C:** Angiography may be useful in diagnosing complications of uveitis such as retinal vasculitis, but it is not the initial investigation of choice for chronic uveitis.

**Clinical Pearl / High-Yield Fact**
Chronic uveitis in children is often associated with underlying autoimmune diseases, and a thorough diagnostic evaluation is essential to identify the underlying cause.

**Correct Answer:** C. Angiography