This disease is also known as Bietti's crystalline corneoretinal dystrophy.

We know from family studies that BCD is mainly inherited in an autosomal recessive manner. This means that an affected person will receive one non-working gene from each of his or her parents. A person who inherits a non-working gene from just one parent will be a carrier, but will not develop the disease. A person with BCD syndrome passes one gene on to each of his or her children. However, unless the person has children with a different carrier of BCD genes, the individual's children are not at risk of developing the disease.

In September 2000, NEI researchers reported that the BCD gene was located on chromosome # 4. In this region of chromosome # 4, there are hundreds of genes. Researchers are now looking for which of the genes in this region of chromosome # 4 causes BCD. Finding the gene can shed light on the composition of the crystals in the corneas of patients with BCD and the cause of the disease.

In March 2004, NEI researchers identified the BCD gene, now called CYP4V2. Researchers believe this gene plays a role in fatty acid and steroid metabolism. This is consistent with findings from biochemical studies in patients with BCD.

The symptoms of BCD include: crystals in the cornea (the clear covering of the eye); yellow, shiny deposits on the retina; and progressive atrophy of the retina, choriocapillaries and choroid (the back layers of the eye). This usually leads to progressive night blindness and narrowing of the visual field. BCD is a rare disease and appears to be more common in people of Asian descent.

People with BCD have crystals in some of their white blood cells (lymphocytes) that can be seen with an electron microscope. Researchers have not been able to determine exactly what substance these crystalline deposits consist of. Their presence does not appear to harm the patient in any other way, except to affect vision.

At present, there is no cure for BCD. Scientists hope that gene research findings will be helpful in finding treatments for patients with BCD.