Choroidal Lesions Preceding Symptom Onset in Birdshot Chorioretinopathy

Birdshot chorioretinopathy was first characterized by Ryan and Maumenee¹ as a chronic intraocular inflammatory condition with discrete, depigmented spots scattered throughout the fundus; mild vitritis; and vasculitis. A very strong association of this condition with the HLA-A29 gene and electrophysiologic abnormalities have since been described.^2,3

In most cases, the patient's initial symptoms are blurred vision, floaters, and/or photopsia and ocular signs consistent with birdshot chorioretinopathy.^1,4,5 A few reports have described the appearance of the classic fundal spots long after the onset of symptoms, inflammation, and vasculitis, but these seem to be in the minority.⁶ We are unaware of any report of the appearance of the classic fundal lesions of birdshot chorioretinopathy prior to the onset of symptoms. Herein we describe such a case.

A 35-year-old white man was first seen with a 3-week history of bilateral floaters. There were no associated or preceding ocular or systemic symptoms. His history included moderate myopia and blunt left ocular trauma in early childhood, after which a small scar at the posterior pole associated with decreased visual acuity was noted. Follow-up after this trauma revealed no change in either the scar or visual acuity.

Initial examination findings revealed a best-corrected visual acuity of 6/5 OD and 6/12 OS. Neither eye had dilated conjunctival vessels. Anterior segment examination revealed a trace of cells bilaterally, very few fine inferior keratitic precipitates, and no granulomatous changes. A mild to moderate vitritis was noted in both eyes. Fundal examination (Figure 1) revealed large areas of pale, flat depigmented lesions typical of birdshot chorioretinopathy, associated with a few isolated areas of retinal vasculitis and intraretinal hemorrhages bilaterally. An old atrophic scar was noted in the left macula, with the right macula appearing normal. There were no vitreal snow balls, snow banking, punched-out chorioretinal scars, nor any other complications.

Investigations included a full blood examination and film, calcium levels, syphilis serology, angiotensin-converting enzyme assay, chest radiography, and HLA-A29 typing. All results were normal except for the HLA-A29 typing, which was positive. Electrophysiology revealed delayed scotopic blue and photopic red b wave amplitudes. Fluorescein angiography revealed areas of vasculitis and typical late staining of the birdshot lesions.

Six months prior to the onset of symptoms, the patient, who works in an eye research institution, volunteered to have his fundi photographed for staff training purposes. Review of these photographs revealed his preexisting left macular scar and the presence of the typical depigmented birdshot choroidopathy lesions, retinal hemorrhages, and patchy retinal vasculitis (Figure 2).

Typically, the multiple depigmented lesions of birdshot chorioretinopathy are seen at the same time as the patient's initial examination for onset of symptoms.^1,4,5 This case appears to be a typical manifestation of birdshot chorioretinopathy. It was purely coincidental that fundus photographs were taken 6 months prior to the onset of symptoms. It is quite possible that the fundal lesions of birdshot chorioretinopathy precede the onset of symptoms by some months but remain undetected in an asymptomatic subject who has no reason to be seen by an ophthalmologist.

The pathogenesis of birdshot chorioretinopathy remains unknown but there are several theories.^1,5,6 Some place the disease focus in the choroid, which is supported by indocyanine green angiography findings.⁷ However, fluorescein angiography and electrodiagnostic findings implicate inner retinal dysfunction secondary to retinal vasculitis.^1,3,7 Our patient is interesting in that he shows that both the retinal vasculitis and choroidal lesions can be present very early in the disease process.

Correspondence: Dr Guymer, Macular Research Unit, Centre for Eye Research Australia, 32 Gisborne St, East Melbourne, Victoria 3002, Australia (rhg@unimelb.edu.au).

Financial Disclosure: None reported.