Birdshot Chorioretinopathy is a rare form of bilateral posterior uveitis, accounting for between 1 – 3% of all uveitis cases. A slight female predominance has been reported. The disease is uncommon in children.
Birdshot Chorioretinopathy causes severe, progressive inflammation of both the choroid and the retina. The name of the disease stems from the hypopigmentation pattern of the lesion on the retina, which resembles the impacts from a shotgun. Symptoms of Birdshot Chorioretinopathy include retinal vasculitis, particulate matter in the vitreous or vitreous inflammation, macular edema, flashing lights in the eyes, night blindness and loss of color vision. A frequent prognosis is complete loss of visual acuity.
Birdshot Chorioretinopathy has the strongest association to the HLA-A*29 antigen. More than 95% of patients carry the HLA-A*29 antigen with the relative risk of HLA-A*29 carriers developing Birdshot Chorioretinopathy being estimated at between 50 and 250. The mechanism by which HLA-A*29 confers susceptibility to Birdshot Chorioretinopathy is unknown. Proposals include antigen specific molecular mimicry following an infection or a role for retinal S-Antigen.
The presence of HLA-A*29 alone is not sufficient for a diagnosis of Birdshot Chorioretinopathy, as there are many cases of patients who do not carry HLA-A*29. Nonetheless the strong association suggests that genetic testing for HLA-A*29 is useful as a supportive finding as part of the diagnosis.