A 12-year-old boy is evaluated for reduced vision in both eyes. Fundus shows bilateral yellowish egg-yolk lesions at the fovea. Electroretinogram is normal but electro-oculogram shows a severely reduced light peak. Which statement about this disorder is correct?

• A The Arden ratio is typically below 1.5
• B The ERG becomes extinguished in advanced disease
• C The causative gene is BEST1 encoding bestrophin ✓
• D It is inherited in an autosomal recessive pattern

Explanation

Best vitelliform macular dystrophy is caused by mutations in BEST1 on chromosome 11, encoding bestrophin in the retinal pigment epithelium, and is inherited autosomal dominantly. The hallmark electrophysiology is a grossly abnormal EOG with a normal ERG, reflecting diffuse RPE dysfunction despite preserved photoreceptors. An Arden ratio below 1.5 indicates severe generalized RPE disease seen in widespread retinal degenerations, whereas Best shows a reduced but not usually extinguished light peak, and the ERG remains normal even in advanced stages.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.