Choroideremia

Choroideremia

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Choroideremia is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • Choroidal Sclerosis
  • Progressive Choroidal Atrophy
  • Progressive Tapetochoroidal Dystrophy
  • TCD

Disorder Subdivisions

  • None

General Discussion

Choroideremia is a genetic disorder of sight that usually affects males. Female carriers may have mild symptoms without loss of vision. Major symptoms include a progressive loss of the peripheral field of vision and night blindness. Night blindness is usually the first noticeable symptom, usually occurring during childhood.

Symptoms

Choroideremia is characterized by extensive loss of all retinal layers in the eye. This disorder usually begins during childhood with wasting (atrophy) of the pigmented retinal epithelium, retina, and choroid of the eye. The retina is the light-sensitive, most internal surface of the eyeball consisting of many, nerve-containing layers. A layer of single pigmented cells is next outside the retina. The choroid is the next vascular layer (membrane) located outside the retina and inside the "white" section of the eye (sclera). The choroid contains many small branches of vessels called the choriocapillaries.



Degeneration of the vessels of the choroid and functional damage to the retina occur later in life and usually lead to progressive peripheral visual field loss and eventual blindness. The symptoms of Choroideremia may vary greatly between affected individuals. Female carriers usually have very mild symptoms without vision loss.

Causes

Choroideremia is an X-linked recessive genetic condition. X-linked recessive disorders are caused by an abnormal gene on the X chromosome. Females have two X chromosomes but one is 'turned off' and all of the genes on that chromosome are inactivated. Females who have a disease gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not show symptoms of the disorder because it is usually the X chromosome with the abnormal gene that is 'turned off'. Males have one X chromosome and if they inherit an X chromosome that contains a disease gene, they will develop the disease. Males with X-linked disorders pass the disease to all of their daughters, who will be carriers. Males can not pass the X-linked gene to their sons because males always pass their Y chromosome instead of their X chromosome to male offspring. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease, and a 25% chance to have an unaffected son.



In 1991, Dr. Frans Cremers of the University of Nijmegen in the Netherlands isolated the gene responsible for Choroideremia. The gene makes a protein call Rab escort protein 1. This discovery may lead to a prenatal test and to treatment for the disease.

Affected Populations

Choroideremia affects males. Female carriers are generally asymptomatic. However, a small number of females have developed the disorder as a result of a genetic process that inactivates the normal gene and leaves only the dysfunctional gene active. In the Salla area of northern Finland, an unusually high concentration of cases has occurred, affecting approximately one in forty persons.

Standard Therapies

Treatment of Choroideremia is symptomatic and supportive. Organizations providing services to sight-impaired people will be of help to patients and their families. Genetic counseling is recommended for families affected by this disorder.

Investigational Therapies

Studies of families with Choroideremia are underway to determine the gene changes (mutations) responsible for the disorder. There is no common mutation that is found in all cases of choroideremia.



This disease entry is based upon medical information available through March 2000. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.



Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.



For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:



Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com

References

TEXTBOOKS

Kanski JJ., ed. Clinical Ophthalmology, 4th ed. Woburn, MA: Butterworth-Heinemann; 1999:453-54.



REVIEW ARTICLES

Seabra MC, Mules EH, Hume AN. Rab GTPases, intracellular traffic and disease. Trends Mol Med. 2002;8:23-30.



Alory C, Balch WE. Organization of the Rab-GDI/CHM superfamily: the functional basis of choroideremia disease. Traffic. 2001;2:532-43.



Pereira-Leal JB, Hume AN, Seabra MC. Prenylation of Rab-GTPases: molecular mechanisms and involvement in genetic disease. FEBS Lett. 2001;498:197-200.



JOURNAL ARTICLES

Roberts MF, Fishman GA, Roberts DK, et al. Retrospective, longitudinal, and cross-sectional study of visual acuity impairment in choroideraemia. Br J Ophthalmol. 2002;86:658-62.



Grover S, Alexander KR, Fishman GA, et al. Comparison of intraocular light scatter in carriers of choroideremia and X-linked retinitis pigmentosa. Ophthalmology. 2002;109:159-63.



Laderman DJ, Szlyk JP, Kelsch R, et al. A curriculum for training patients with peripheral visual field loss to use bioptic amorphic lenses. J Rehabil Res Dev. 2000;37:607-19.



Hirakawa H, et al., Progression of defects in the central 10-degree visual field of patients with retinitis pigmentosa and choroideremia. Am J Ophthalmol. 1999;127:436-42.



Majid MA, et al., Unusual macular findings in a known choroideremia carrier. Eye. 1998;12:740-41.



MacDonald IM, et al., A practical diagnostic test for choroideremia. Ophthalmology. 1998;105:1637-40.



MacDonald IM, et al., Histopathology of the retinal pigment epithelium of a female carrier of choroideremia. Can J Ophthalmol. 1997;32:329-33.



Tallman KB, et al., A case study of choroideremia highlighting differential diagnosis and management with Fresnel prism therapy. J Am Optom Assoc. 1996;67:421-29.



FROM THE INTERNET

McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). Baltimore, MD; Johns Hopkins University Press: Entry Number; 303100: Last Update; 5/1/02, Entry No: 300390; Last Update; 5/1/02.



Choroideremia Research Foundation. Technical Description of Choroideremia, CHM. nd. 9pp.

www.choroideremia.org/CHMtechy.htlm



MacDonald I. (Ophthalmology - University of Alberta). Choroideremia Diagnostic Testing. nd. 1p.

www.ualberta.ca/~ophthalm/choroid.htm



CONSUMER RESOURCES

Choroideremia Research Foundation. Basic Description of Choroideremia. Nd. 2pp.

www.choroideremia.org/CHMplain.html



Choroideremia. EyeMDLink.com. nd. 1p.

www.eyemdlink.com/Condition.asp?ConditionID=108



Health-Nexus. Choroideremia. nd. 2pp.

www.health-nexus.com/choroideremia.htm

Resources

Lighthouse International

111 E 59th St

New York, NY 10022-1202

Tel: (800)829-0500

Email: info@lighthouse.org

Internet: http://www.lighthouse.org



National Association for Parents of Children with Visual Impairments (NAPVI)

P.O. Box 317

Watertown, MA 02272-0317

Tel: (617)972-7441

Fax: (617)972-7444

Tel: (800)562-6265

Email: napvi@perkins.org

Internet: http://www.napvi.org



National Federation of the Blind

200 East Wells Street

at Jernigan Place

Baltimore, MD 21230

USA

Tel: (410)659-9314

Fax: (410)685-5653

Email: nfb@nfb.org

Internet: http://www.nfb.org



American Foundation for the Blind

2 Penn Plaza

Suite 1102

New York, NY 10121

Tel: (212)502-7600

Fax: (888)545-8331

Tel: (800)232-5463

TDD: (212)502-7662

Email: afbinfo@afb.net

Internet: http://www.afb.org



American Council of the Blind

2200 Wilson Boulevard

Suite 650

Arlington, VA 22201

Tel: (202)467-5081

Fax: (202)465-5085

Tel: (800)424-8666

Email: mailman@acb.org

Internet: http://www.acb.org/



NIH/National Eye Institute

31 Center Dr

MSC 2510

Bethesda, MD 20892-2510

United States

Tel: (301)496-5248

Fax: (301)402-1065

Email: 2020@nei.nih.gov

Internet: http://www.nei.nih.gov/



Choroideremia Research Foundation, Inc.

23 East Brundreth St

Springfield, MA 01109

Tel: (413)781-2274

Email: info@choroideremia.org

Internet: http://www.choroideremia.org



Eye Cancer Foundation

115 East 61st Street, Suite 5B

New York, NY 10021

Tel: (212)832-7297

Fax: (212)888-4030

Email: contactus@eyecarefoundation.org

Internet: http://www.eyecarefoundation.org



MD Support - The Eyes of the Macular Degeneration Community

3600 Blue Ridge Blvd

Grandview, MO 64030

USA

Tel: (816)761-7080

Fax: (816)761-7080

Email: director@mdsupport.org

Internet: http://www.mdsupport.org



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



Foundation Fighting Blindness (Canada)

890 Yonge Street, 12th Floor

Toronto, Ontario, M4W 3P4

Canada

Tel: 4163604200

Fax: 4163600060

Tel: 8004613331

Email: info@ffb.ca

Internet: http://www.ffb.ca



The Choroideremia Research Foundation Canada, Inc.

16 Candlewood Drive

Brantford

Ontario, N3R 6A1

Canada

Tel: 5197588047

Fax: 5197580448

Email: info@choroideremia.ca

Internet: http://www.choroideremia.ca



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use . How this information was developed to help you make better health decisions.

Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.