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HLA-B27–Associated Uveitis


Key Concepts

  • Human leukocyte antigen (HLA)-B27–associated uveitis is the most common cause of hypopyon uveitis in North America.

  • HLA-B27–associated uveitis is nongranulomatous, anterior, and often severe.

  • It is typically of sudden onset and limited duration but occasionally becomes chronic.

  • It typically occurs in one eye at a time, although it may occasionally be bilateral, particularly the first episode.

  • Uveitis or arthritis may be triggered in HLA B27–positive individuals by exposure to organisms such as Salmonella , Shigella , Chlamydia , and Yersinia.

  • HLA-B27 testing is appropriate in the setting of acute nongranulomatous anterior uveitis.

The human leukocyte antigen (HLA) system (the major histocompatibility complex [MHC] in humans) is controlled by genes located on chromosome 6 and plays a crucial role in determining the immune response. Of the HLA types that have been found to be linked with autoimmune diseases, perhaps one of the best known in ophthalmology is the association between acute anterior uveitis (AAU) and HLA-B27. HLA-B27–associated AAU can occur as an isolated condition but is commonly associated with spondyloarthropathies such as ankylosing spondylitis, reactive arthritis, psoriatic arthritis, inflammatory bowel disease, and unspecified spondyloarthropathies.

Epidemiology

The prevalence of HLA-B27 in the general population varies significantly among ethnic groups. Although it is virtually absent among sub-Saharan Africans, South American Indians, and Australian Aborigines, the highest prevalence of HLA-B27 seropositivity worldwide is found in the Pawaia tribe in Papua New Guinea (53%). A US population-based study in 2009 revealed that 7.5% of non-Hispanic whites, 4.6% of Mexican Americans, and 1.1% of non-Hispanic blacks were seropositive.

Acute anterior uveitis, described as the sudden onset of a limited-duration episode of intraocular inflammation of the iris and/or ciliary body, represents the most frequently occurring form of uveitis. , However, the incidence and prevalence of anterior uveitis vary according to the study population, generally accounting for 80%–90% of cases from comprehensive ophthalmology practices with a lower percentage in tertiary care centers. In the general population, the lifetime cumulative incidence of AAU has been reported as 0.2% and rises to 1% in the HLA-B27–positive population. HLA-B27–associated AAU is the most frequently identified cause of anterior uveitis and accounts for 40%–82.5% of AAU.

All patients with a first episode of AAU with symptoms of spondyloarthropathy, especially lower back pain or bloody stools, and patients with severe or recurrent episodes of AAU should be tested for HLA-B27. The importance of this testing stems from the systemic morbidity from spondyloarthropathy, prognostic implications, and therapeutic planning. A thorough history with a review of systems—particularly rheumatologic, gastrointestinal, and dermatologic manifestations—is essential in order to uncover any associated systemic inflammatory conditions.

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