Birdshot chorioretinopathy: current knowledge and new concepts in pathophysiology, diagnosis, monitoring and treatment

Abstract

Birdshot chorioretinopathy (BCR) is a rare form of chronic, bilateral, posterior uveitis with a distinctive clinical phenotype, and a strong association with HLA-A29. It predominantly affects people in middle age. Given its rarity, patients often encounter delays in diagnosis leading to delays in adequate treatment, and thus risking significant visual loss. Recent advances have helped increase our understanding of the underlying autoimmune mechanisms involved in disease pathogenesis, and new diagnostic approaches such as multimodality imaging have improved our ability to both diagnose and monitor disease activity. Whilst traditional immunosuppressants may be effective in BCR, increased understanding of immune pathways is enabling development of newer treatment modalities, offering the potential for targeted modulation of immune mediators. In this review, we will discuss current understanding of BCR and explore recent developments in diagnosis, monitoring and treatment of this disease. Synonyms for BCR: Birdshot chorioretinopathy, Birdshot retinochoroiditis, Birdshot retino-choroidopathy, Vitiliginous choroiditis. Orphanet number: ORPHA179 OMIM: 605808.

Keywords: Birdshot chorioretinopathy; HLA-A29; Immunomodulatory therapy; Multimodality diagnostic imaging; T-helper 17.

Fig. 1

Fundus photomontage of right (a) and left (b) eyes of a patient with BCR revealing both classic creamy ovoid lesions and the linear streaks of more advanced lesions

Fig. 2

Wide-field imaging such as with the Optos™ of right (a) and left (b) eyes of a patient with BCR is helpful in revealing the distribution of lesions, and may make the diagnosis more obvious than on standard field fundus photography

Fig. 3

Detection of novel retinal morphologic parameters using extramacular optical coherence tomographic (OCT) scanning protocols. a Near-infrared fundus image and inferior extramacular OCT B-scan reveal patchy disruption of the photoreceptor inner segment/outer segment (IS/OS) junction. b Near-infrared fundus image and inferior extramacular OCT B-scan reveal generalized thinning/loss of the retinal architecture, generalized loss of the IS/OS junction, and the presence of discrete outer retinal hyperreflective foci. c Near-infrared fundus image and temporal extramacular OCT B-scan reveal the transition zone between a grossly normal and a diseased retina. (With permission from Keane et al.) [51]