CYP4V2 and Bietti crystalline dystrophy: BCD is a specific type of retinitis pigmentosa with autosomal recessive inheritance caused by mutations in CYP4V2. 8 The CYP4V2 protein is produced in multiple body tissues but is particularly abundant in the RPE.9,10 CYP4V2 is an omega 3-polyunsaturated medium-chain fatty acid hydroxylase that hydrolyzes docosahexaenoic and eicosapentaenoic acid in the eye.9 The photoreceptor outer segment contains large amounts of lipids that can be esterified to form docosahexaenoic acid, eicosapentaenoic acid, and other fatty acids.