Bietti crystalline dystrophy or BCD is a disorder where there are numerous small, yellow, or white crystal-like deposits of fatty compounds in the retina. These deposits are dangerous because they cause damage to the retina which can result in progressive vision loss. BCD is a rare autosomal recessive ocular disease.
People with Bietti crystalline dystrophy may notice vision problems when they are in their early teens or twenties. They can experience reduced visual acuity or loss of sharp vision, night blindness or difficulty seeing in dim light, visual field loss or loss of areas of vision, and even side or peripheral vision. Impaired color vision may also occur.
Most people with Bietti crystalline dystrophy become legally blind in their forties or fifties. The severity and progression of symptoms differ among affected individuals even if they are within the same family. Each eye has a different rate when it comes to vision problems. There are affected individuals who can retain some degree of vision, commonly the center of the visual field.
Even if some affected individuals can retain some degree of vision, the problem is they have blurry vision that cannot be corrected by contact lenses or glasses. Low vision is a condition where vision impairment cannot be improved with corrective lenses.
Causes of Bietti Crystalline Dystrophy
The cause of Bietti crystalline dystrophy is the mutation in the CYP4V2 gene which is responsible for giving instructions for making a member of the cytochrome P450 family of enzymes. The said enzymes are included in the formation and breakdown of molecules and chemicals in the cells. A multi-step process called fatty acid oxidation involves CYP4V2 enzyme where lipids are converted into energy when broken down.
The CYP4V2 gene mutations cause Bietti crystalline dystrophy to impair the function of enzymes which is believed to affect lipid breakdown. The reason behind why the signs and symptoms of Bietti crystalline dystrophy occur is unknown. There is no exact reason why the severity of signs and symptoms differ among individuals with the same CYP4V2 gene mutation.
Can I Inherit Bietti Crystalline Dystrophy?
The estimated frequency of this condition to occur is 1 in 67,000 people. It is common for those who have Chinese and Japanese backgrounds to have this condition. Bietti crystalline dystrophy is inherited in an autosomal recessive pattern. It means that parents of an individual who has an autosomal recessive condition carry one copy of the mutated gene but do not show any signs and symptoms of the condition.