birdshot retinochoroidopathy
Aetiology Unknown. HLA-A29 is present in up to 95%, suggesting a strong immunogenetic predisposition; HLA-A29 has been estimated to increased the relative risk of developing birdshot retinochoroidopathy 200-fold. One series of patients had a strong cell-mediated in vitro response to purified S-antigen, which is found in photoreceptors and causes experimental autoimmune uveitis (EAU) when injected in animals. BRC and EAU share several features including the appearance of deep focal lesions, periphlebitis, and intraocular inflammation, suggesting autoimmunity
DiffDx Pars planitis, APMPPE, serpiginous choroiditis, sarcoidosis, diffuse unilateral subacute neuroretinitis, Behçet’s disease, primary ocular-CNS lymphoma, Whipples disease, multifocal choroiditis and panuveitis, Lyme disease
Management Most cases are resistant to treatment; some cases may respond to steroids, but may recur if discontinued; because of the complications associated with long-term use, steroids are recommended only when visually significant CME or vitritis is present. Administration of periocular steroids may be helpful for the treatment of cystoid macular oedema and avoids unwanted systemic side-effects; other therapies include acetazolamide, cyclosporine in combination with other agents may resolve the macular oedema, reduce vitritis, improve vision, and result in fewer recurrences
Prognosis Most patients experience visual loss to 20/200 or worse in at least one eye; depigmentation of the RPE may be responsible for the vitiliginous spots seen clinically