A 28-year-old man with a history of ankylosing spondylitis presents with acute anterior uveitis. A 45-year-old woman with sarcoidosis presents with chronic posterior uveitis. Which finding best distinguishes the typical presentation of HLA-B27–associated anterior uveitis from sarcoidosis-associated posterior uveitis?

Explanation

## Clinical Presentation: HLA-B27–Associated Anterior Uveitis vs. Sarcoidosis-Associated Posterior Uveitis ### Key Distinction: Symptom Onset and Severity **Key Point:** The clinical presentation pattern — acute, painful anterior uveitis in HLA-B27–associated disease versus insidious, asymptomatic posterior uveitis in sarcoidosis — is the most reliable discriminator between these two common forms of uveitis. ### Comparative Table | Feature | HLA-B27–Associated Anterior Uveitis | Sarcoidosis-Associated Posterior Uveitis | |---------|-------------------------------------|------------------------------------------| | **Onset** | Acute (hours to days) | Insidious (weeks to months) | | **Pain** | Severe | Minimal or absent | | **Photophobia** | Marked | Absent or mild | | **Floaters** | Absent or minimal | Prominent (often patient's first complaint) | | **Vision loss** | Mild to moderate | Can be severe (due to macular involvement) | | **Anterior chamber** | Marked inflammation with hypopyon (common) | Minimal inflammation | | **Vitritis** | Minimal | Prominent | | **Keratic precipitates** | Non-granulomatous (fine) or granulomatous | Granulomatous (mutton-fat) | | **Recurrence** | Frequent (70–80% recur) | Less frequent | | **Laterality at onset** | Often unilateral initially | Often bilateral | ### High-Yield Clinical Pearls **Clinical Pearl:** HLA-B27–associated anterior uveitis is the classic "painful red eye" — the patient arrives in distress with photophobia and pain. In contrast, sarcoidosis-associated posterior uveitis is often discovered incidentally during routine eye examination; the patient may be unaware of vision loss until it is significant. **High-Yield:** HLA-B27–associated uveitis is **acute and symptomatic**; sarcoidosis-associated uveitis is **chronic and asymptomatic** — this is the key discriminator. ### Mnemonic **Mnemonic:** **HLA-B27 = ACUTE PAIN** (Anterior, Chronic recurrence, Unilateral initially, Terrible pain, Episodic); **Sarcoidosis = SILENT SIGHT** (Subtle onset, Insidious, Lateral involvement, Elevated vision loss, Negligible pain, Thoracic findings) ### Pathophysiologic Basis HLA-B27–associated uveitis is driven by acute immune response to bacterial antigens (molecular mimicry with enteric pathogens), causing rapid anterior segment inflammation. Sarcoidosis-associated uveitis is a chronic granulomatous process with slow accumulation of inflammatory cells in the posterior segment, often without acute symptoms until vision is compromised. [cite:Kanski Clinical Ophthalmology 9e Ch 8; Moorfields Manual of Ophthalmology]