Objective: To provide the clinicopathologic findings of a patient who developed the clinical characteristics of Best disease (typically considered a juvenile macular degeneration) at the age of 75 years after being documented to be ophthalmoscopically normal at the age of 51 years.
Design: A member of a large family with Best disease, possessing a Y227N mutation in the VMD2 gene (the gene responsible for the disease, which encodes the bestrophin protein), developed small vitelliform lesions in both eyes at the age of 75 years and later developed yellow flecklike depositions at the level of the retinal pigment epithelium (RPE), which were also identified in fundus photographs of family members. The patient died at the age of 93 years, and the histological features of the macular lesion and peripheral flecks were examined.
Results: Histopathologically, the retinal outer nuclear layer was attenuated, particularly in the macula. This attenuation was frequently associated with normal RPE. A large area of photoreceptor degeneration was present in the central macula, with loss of the underlying RPE cells. Outside of this region, the RPE density was within normal limits. The peripheral flecks were clusters of basal laminar deposits and drusen. Bestrophin immunohistochemistry revealed labeling along both the basolateral and apical membranes of the RPE.
Conclusions: Findings characteristic of Best disease may not manifest in a molecularly affected individual until late in life. Mutations in bestrophin appear to lead to extracellular deposit formation outside the macula in some families. The distribution of bestrophin in the RPE suggests that the protein may be mistargeted in those with Best disease who have the Y227N mutation, and that this may be a cause of the associated RPE and photoreceptor dysfunction.