Which of the following HLA types is most strongly associated with Behçet disease?

Explanation

## HLA Associations in Uveitis — Behçet Disease **Key Point:** HLA-B51 is the most strongly associated HLA allele with Behçet disease, with a relative risk of 10–100 in affected populations, particularly in Mediterranean, Middle Eastern, and East Asian populations. ### HLA Associations in Major Uveitic Entities | Disease | HLA Type | Relative Risk | Geographic Association | |---------|----------|---------------|------------------------| | **Behçet disease** | **HLA-B51** | 10–100 | Mediterranean, Middle East, East Asia | | Ankylosing spondylitis | HLA-B27 | 50–100 | Northern European ancestry | | Acute anterior uveitis (idiopathic) | HLA-B27 | 5–10 | Caucasian populations | | Birdshot chorioretinopathy | HLA-A29 | >95% | Caucasian, Northern European | | Celiac disease-associated uveitis | HLA-DQ2 | High | Celiac disease patients | **High-Yield:** HLA-B51 positivity is found in 60–90% of Behçet disease patients in endemic regions (Turkey, Iran, Japan), making it a useful diagnostic marker. However, it is neither sensitive nor specific enough to be diagnostic alone. **Clinical Pearl:** Behçet disease is a chronic, relapsing systemic vasculitis affecting small and medium vessels. Ocular involvement (uveitis) occurs in 50–70% of patients and is often the most disabling manifestation, particularly in men. **Mnemonic: "Behçet = B51"** — The disease name starts with "B" and the HLA type is "B51." ### Diagnostic Criteria for Behçet Disease (International Study Group) - **Recurrent oral ulcers** (mandatory criterion) + 2 of the following: - Recurrent genital ulcers - Ocular lesions (typically posterior uveitis, retinal vasculitis) - Skin lesions (erythema nodosum, pseudofolliculitis, papulopustules) - Positive pathergy test [cite:Kanski Clinical Ophthalmology 8e Ch 11]