Bietti crystalline dystrophy

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 under-diagnosed 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.

Related Gene(s)

Changes in this gene are associated with Bietti crystalline dystrophy.

CYP4V2

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.

Canadian Ophthalmological Society: Low Vision Rehabilitation (http://www.eyesite.ca/english/public-information/eye-conditions/pdfs/LowVision_e.pdf)
Gene Review: Bietti Crystalline Dystrophy (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=bietti-cd)
Genetic Testing Registry: Bietti crystalline corneoretinal dystrophy (http://www.ncbi.nlm.nih.gov/gtr/conditions/C1859486)

You might also find information on the diagnosis or management of Bietti crystalline dystrophy in Educational resources (http://www.ghr.nlm.nih.gov/condition/bietti-crystalline-dystrophy/show/Educational+resources) and Patient support (http://www.ghr.nlm.nih.gov/condition/bietti-crystalline-dystrophy/show/Patient+support).

General information about the diagnosis (http://ghr.nlm.nih.gov/handbook/consult/diagnosis) and management (http://ghr.nlm.nih.gov/handbook/consult/treatment) of genetic conditions is available in the Handbook. Read more about genetic testing (http://ghr.nlm.nih.gov/handbook/testing), particularly the difference between clinical tests and research tests (http://ghr.nlm.nih.gov/handbook/testing/researchtesting).

To locate a healthcare provider, see How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) 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.

MedlinePlus - Health information
Health Topic: Retinal Disorders (http://www.nlm.nih.gov/medlineplus/retinaldisorders.html)
Additional NIH Resources - National Institutes of Health
- National Eye Institute: Facts About Bietti's Crystalline Dystrophy (http://www.nei.nih.gov/health/biettis/bietti.asp)
- National Eye Institute: Low Vision (http://www.nei.nih.gov/lowvision/)
Educational resources - Information pages
- American Academy of Ophthalmology: What is Low Vision? (http://www.geteyesmart.org/eyesmart/diseases/low-vision.cfm)
- American Optometric Association: Low Vision (http://www.aoa.org/x5240.xml)
- Orphanet (http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=41751)
- The University of Arizona College of Medicine (http://disorders.eyes.arizona.edu/handouts/bietti-crystalline-corneoretinal-dystrophy)
Patient support - For patients and families
- American Foundation for the Blind: Low Vision (http://www.afb.org/section.aspx?SectionID=26)
- Family Village: Blind/Visual Impairment (http://www.familyvillage.wisc.edu/lib_blnd.htm)
- Lighthouse International: All About Low Vision (http://lighthouse.org/about-low-vision-blindness/all-about-low-vision/)
- Retina International (http://www.retina-international.org/)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

Gene Reviews - Clinical summary (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=bietti-cd)
Genetic Testing Registry - Repository of genetic test information
- Genetic Testing Registry: Bietti crystalline corneoretinal dystrophy (http://www.ncbi.nlm.nih.gov/gtr/conditions/C1859486)
ClinicalTrials.gov - Linking patients to medical research (http://clinicaltrials.gov/ct2/results?cond=%22Bietti%20crystalline%20dystrophy%22)
PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/pubmed?term=(bietti%20crystalline%20dystrophy%5BTIAB%5D)%20AND%20english%5Bla%5D%20AND%20human%5Bmh%5D%20AND%20%22last%203600%20days%22%5Bdp%5D)
OMIM - Genetic disorder catalog (http://omim.org/entry/210370)

What other names do people use for Bietti crystalline dystrophy?

BCD
Bietti crystalline corneoretinal dystrophy
Bietti crystalline retinopathy
Bietti tapetoretinal degeneration with marginal corneal dystrophy

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines (http://ghr.nlm.nih.gov/ConditionNameGuide) and How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What if I still have specific questions about Bietti crystalline dystrophy?

Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/GARD/).

What glossary definitions help with understanding Bietti crystalline dystrophy?

autosomal ; autosomal recessive ; cell ; cytochrome P450 ; enzyme ; gene ; 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 (http://www.ghr.nlm.nih.gov/glossary).

References

Li A, Jiao X, Munier FL, Schorderet DF, Yao W, Iwata F, Hayakawa M, Kanai A, Shy Chen M, Alan Lewis R, Heckenlively J, Weleber RG, Traboulsi EI, Zhang Q, Xiao X, Kaiser-Kupfer M, Sergeev YV, Hejtmancik JF. Bietti crystalline corneoretinal dystrophy is caused by mutations in the novel gene CYP4V2. Am J Hum Genet. 2004 May;74(5):817-26. Epub 2004 Mar 23. (http://www.ncbi.nlm.nih.gov/pubmed/15042513?dopt=Abstract)
Mamatha G, Umashankar V, Kasinathan N, Krishnan T, Sathyabaarathi R, Karthiyayini T, Amali J, Rao C, Madhavan J. Molecular screening of the CYP4V2 gene in Bietti crystalline dystrophy that is associated with choroidal neovascularization. Mol Vis. 2011;17:1970-7. Epub 2011 Jul 20. (http://www.ncbi.nlm.nih.gov/pubmed/21850171?dopt=Abstract)
Mansour AM, Uwaydat SH, Chan CC. Long-term follow-up in Bietti crystalline dystrophy. Eur J Ophthalmol. 2007 Jul-Aug;17(4):680-2. (http://www.ncbi.nlm.nih.gov/pubmed/17671952?dopt=Abstract)
Rossi S, Testa F, Li A, Iorio VD, Zhang J, Gesualdo C, Corte MD, Chan CC, Fielding Hejtmancik J, Simonelli F. An atypical form of Bietti crystalline dystrophy. Ophthalmic Genet. 2011 Jun;32(2):118-21. doi: 10.3109/13816810.2011.559653. Epub 2011 Mar 8. (http://www.ncbi.nlm.nih.gov/pubmed/21385027?dopt=Abstract)
Xiao X, Mai G, Li S, Guo X, Zhang Q. Identification of CYP4V2 mutation in 21 families and overview of mutation spectrum in Bietti crystalline corneoretinal dystrophy. Biochem Biophys Res Commun. 2011 Jun 3;409(2):181-6. doi: 10.1016/j.bbrc.2011.04.112. Epub 2011 May 1. (http://www.ncbi.nlm.nih.gov/pubmed/21565171?dopt=Abstract)

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? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.



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