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Bietti crystalline dystrophy
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Reviewed November 2012
What is Bietti crystalline dystrophy?
Bietti crystalline dystrophy is a disorder in which numerous small, yellow or white crystal-like deposits of fatty (lipid) compounds accumulate in the light-sensitive tissue that lines the back of the eye (the retina). The deposits damage the retina, resulting in progressive vision loss.
People with Bietti crystalline dystrophy typically begin noticing vision problems in their teens or twenties. They experience a loss of sharp vision (reduction in visual acuity) and difficulty seeing in dim light (night blindness). They usually lose areas of vision (visual field loss), most often side (peripheral) vision. Color vision may also be impaired.
The vision problems may worsen at different rates in each eye, and the severity and progression of symptoms varies widely among affected individuals, even within the same family. However, most people with this condition become legally blind by their forties or fifties. Most affected individuals retain some degree of vision, usually in the center of the visual field, although it is typically blurry and cannot be corrected by glasses or contact lenses. Vision impairment that cannot be improved with corrective lenses is called low vision.
How common is Bietti crystalline dystrophy?
Bietti crystalline dystrophy has been estimated to occur in 1 in 67,000 people. It is more common in people of East Asian descent, especially those of Chinese and Japanese background. Researchers suggest that Bietti crystalline dystrophy may be underdiagnosed because its symptoms are similar to those of other eye disorders that progressively damage the retina.
What genes are related to Bietti crystalline dystrophy?
Bietti crystalline dystrophy is caused by mutations in the CYP4V2 gene. This gene provides instructions for making a member of the cytochrome P450 family of enzymes. These enzymes are involved in the formation and breakdown of various molecules and chemicals within cells. The CYP4V2 enzyme is involved in a multi-step process called fatty acid oxidation in which lipids are broken down and converted into energy, but the enzyme's specific function is not well understood. CYP4V2 gene mutations that cause Bietti crystalline dystrophy impair or eliminate the function of this enzyme and are believed to affect lipid breakdown. However, it is unknown how they lead to the specific signs and symptoms of Bietti crystalline dystrophy. For unknown reasons, the severity of the signs and symptoms differs significantly among individuals with the same CYP4V2 gene mutation.
Read more about the CYP4V2 gene.
How do people inherit Bietti crystalline dystrophy?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of Bietti crystalline dystrophy?
These resources address the diagnosis or management of Bietti crystalline dystrophy and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about Bietti crystalline dystrophy?
You may find the following resources about Bietti crystalline dystrophy helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for Bietti crystalline dystrophy?
What if I still have specific questions about Bietti crystalline dystrophy?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding Bietti crystalline dystrophy?
autosomal ; autosomal recessive ; breakdown ; cell ; cytochrome P450 ; enzyme ; gene ; inherited ; lipid ; lipid breakdown ; mutation ; oxidation ; peripheral ; progression ; recessive ; retina ; tissue ; visual acuity
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (5 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.