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Bietti's Crystalline Dystrophy

Bietti's crystalline dystrophy (BCD) is an inherited eye disease named for Dr. G. B. Bietti, an Italian ophthalmologist, who described three patients with similar symptoms in 1937. 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 tends to lead to progressive night blindness and visual field constriction. BCD is a rare disease and appears to be more common in people with Asian ancestry.

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

Causes

From family studies, we know that BCD is inherited primarily in an autosomal recessive fashion. This means that an affected person receives one nonworking gene from each of his or her parents. A person who inherits a nonworking gene from only one parent will be a carrier, but will not develop the disease. A person with BCD syndrome will pass on one gene to each of his or her children. However, unless the person has children with another carrier of BCD genes, the individual's children are not at risk for developing the disease.

In September 2000, researchers reported that the BCD gene had been localized to 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 may shed light on the composition of the crystals found in the corneas of patients with BCD and on what causes the condition.

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

Treatment

At this time, there is no treatment for BCD. Scientists hope that findings from gene research will be helpful in finding treatments for patients with BCD.

 

Reference:

National Eye Institute, USA.