Acute Anterior Uveitis and HLA-B27: What’s New?

■ Acute anterior uveitis (AAU) accounts for 90% of all uveitis cases seen by the general ophthalmologist. ■ About half of all AAU cases are HLA-B27associated. ■ HLA-B27+ AAU represents a distinct clinical entity with important ocular and extraocular consequences. ■ The typical ocular phenotype of HLA-B27+ AAU is that of acute onset, unilateral inflammation of the iris and ciliary body, with a tendency towards recurrent attacks and more severe inflammation, including hypopyon formation. Males are affected more frequently than females. ■ All patients with AAU must have a dilated fundus examination to confirm the diagnosis is anterior uveitis, and careful clinical assessment regarding possible associated systemic inflammatory disease. ■ All patients with AAU should be investigated with HLA-B27 typing, syphilis serology, and a chest X-ray at a minimum. ■ 50% of patients with HLA-B27+ AAU will develop an associated seronegative spondyloarthropathy (SpA), whilst approximately 25% of the patients initially diagnosed with HLA-B27associated systemic disease will develop AAU. ■ HLA-B27 is the strongest known genetic risk factor for AAU. There are multiple subtypes of HLA-B27, which may be differentially associated with disease. ■ In addition to genetic factors, environmental factors play a critical role in the pathogenesis of AAU. ■ Bacterial triggers have been strongly implicated in the development of AAU and recurrent episodes of ocular inflammation. ■ Human uveal antigen-presenting cells express TLR4, the receptor for LPS, and may provide a critical molecular link between microbial triggers and the development of AAU. ■ Topical corticosteroids and cycloplegic agents are the mainstay of treatment.