Bietti’s crystalline dystrophy (BCD) is a rare disease that happens when crystals made of fatty acids build up in your cornea (clear outer layer at the front of the eye) and retina (light-sensitive layer of tissue in the back of the eye).

BCD is an inherited genetic disease, which means that parents pass it down to their children. If you have BCD or it runs in your family, you can get tested for the BCD gene to learn more about the risk of passing it to your child.

How do genes cause BCD?

BCD is caused by changes in a gene called CYP4V2. Experts think this gene affects how the body uses fatty acids, but they’re still studying how this works.

In most cases, you can only get BCD if you have 2 copies of this abnormal (changed) BCD gene — usually 1 inherited from each parent. This type of inheritance is called autosomal recessive inheritance.

If you only inherit 1 abnormal BCD gene and your other copy is normal, you won’t have symptoms of the disease. People with only 1 copy of the abnormal gene are called carriers.

If I have the BCD gene, will I pass it down to my child?

If you have BCD, you’ll always pass down 1 copy of the abnormal gene to each of your children. If you’re a BCD carrier, you have a 1 in 2 chance of passing down the gene to each child.

But your children will only have symptoms if they have a second copy of the abnormal BCD gene. In fact, if 2 BCD carriers have a child together, that child has a 1 in 4 chance of having symptoms of BCD.

Can I get tested for the BCD gene?

Yes, there are genetic tests for the CYP4V2 gene that causes BCD.

If you have BCD or it runs in your family, you can talk with your doctor or a specialist called a genetic counselor to learn more about the risk of passing BCD down to your child.

Last updated: June 22, 2021