THE FUNDUS PHENOTYPE ASSOCIATED WITH THE p.Ala243Val BEST1 MUTATION

To describe a highly recognizable and reproducible retinal phenotype associated with a specific BEST1 mutation-p.Ala243Val.

Retrospective review of consecutive cases where genetic testing has identified p.Ala243Val BEST1 as the cause of disease. Electronic patient records were used to extract demographic, as well as functional and anatomical data. These data were compared with those observed with the most common BEST1 genotype, p.Arg218Cys.

Eight individuals (six families) were identified with the p.Ala243Val BEST1 mutation and seven patients with the pathologic variant p.Arg218Cys. No patients with mutation of codon 243 knowingly had a family history of retinal disease, whereas all patients with the p.Arg218Cys variant did. The maculopathy was bilateral in all cases. The p.Ala243Val mutation was associated with a pattern dystrophy-type appearance, most visible with near-infrared reflectance and fundus autofluorescence imaging. This phenotype was never observed with any other genotype. This mutation was associated with an older median age of symptom onset (median = 42, interquartile range = 22) compared with those harboring the p.Arg218Cys mutation (median = 18, interquartile range = 12; Mann-Whitney U test; P < 0.05). Despite their older age, the final recorded acuity seemed to be better in the p.Ala243Val group (median = 0.55, interquartile range = 0.6475; median = 0.33, interquartile range = 0.358), although this did not reach statistical significance (Mann-Whitney U test; P > 0.05).

The mutation p.Ala243Val is associated with highly recognizable and reproducible pattern dystrophy-like phenotype. Patients develop symptoms at a later age and tend to have better preservation of electrooculogram amplitudes.