HLA-A29 and birdshot chorioretinopathy.

Birdshot chorioretinopathy primarily affects patients of European descent. At least 96%, if not all patients, are HLA-A29 carriers. HLA-A29:01 and HLA-A29:02, the two main subtypes of HLA-A29, differ only by a single mutation. In the general population HLA-A29:02 is most frequent in whites, while HLA-A29:01 is more frequent in Asians. The differential distribution of HLA-A29:01 and HLA-A29:02 has been actively debated as an explanation for the selective development of the disease in patients of European descent, but is no longer a valid argument. Another factor, probably not HLA linked, is either protective in Asians and in Africans or, conversely, triggers an autoimmune reactivity that is possibly present in whites and absent in Asians and in Africans. HLA-A*29:02 transgenic mice in which a spontaneous posterior uveitis is observed after 6 months of age provide further evidence that the HLA-A29 molecule plays a role in the pathogenesis of the disease.