Bietti crystalline dystrophy（BCD）is a rare autosomal recessive inherited retinal disorder caused by mutations in the CYP4V2 gene located on chromosome 4q35.

BCD is distributed worldwide and is common in East Asia. It is the most prevalent RP disease in Asian population.

BCD is a severe blind degenerative retinal disease characterized by numerous intraretinal flash crystalline deposits that are widely distributed in the fundus. Most BCD patients experience onset between the ages of 20 and 40, developing symptoms such as night blindness and decreased vision. By the age of 50 to 60, many patients develop legal blindness.