These genes show various polymorphic forms, one of which is the B27. The HLA-B27 associated uveitic syndrome is the second commonest cause of anterior uveitis, following idiopathic uveitis. Like most of the other conditions associated with the B27 gene, B27 associated acute anterior uveitis also has a higher frequency in males than in females. Classically, B27 associated uveitis presents with sudden onset acute anterior uveitis in a young patient. It starts in one eye but is usually asymmetrically bilateral.
Studies show that it is also associated with higher recurrence rates than the idiopathic variety.
This may take the form of posterior vitritis, vasculitis or papillitis. Because of this, and because in some patients a systemic condition, even though present may not have been diagnosed, it becomes vital to take a detailed history and to conduct a focussed systemic examination of these patients. These conditions are HLA-B27 associated, but although the presence of this gene is extremely helpful in the diagnosis, its absence does not exclude them. The spondyloarthropathies also show considerable clinical overlap, so that sometimes it may be difficult to distinguish between them. It is was traditionally considered more common in males, but it is now recognized that it may be equally common in females, although less severe.