$Unique_ID{BRK03598} $Pretitle{} $Title{Choroideremia} $Subject{Choroideremia Progressive Tapetochoroidal Dystrophy TCD Progressive Choroidal Atrophy Choroidal Sclerosis X-linked Retinitis Pigmentosa Diffuse Choriocapillaris Atrophy Gyrate Atrophy of the Choroid and Retina} $Volume{} $Log{} Copyright (C) 1988, 1989, 1991 National Organization for Rare Disorders, Inc. 525: Choroideremia ** IMPORTANT ** It is possible the main title of the article (Choroideremia) is not the name you expected. Please check the SYNONYMS listing on the next page to find alternate names and disorder subdivisions covered by this article. Synonyms Progressive Tapetochoroidal Dystrophy TCD Progressive Choroidal Atrophy Choroidal Sclerosis Information on the following diseases can be found in the Related Disorders section of this report: X-linked Retinitis Pigmentosa Diffuse Choriocapillaris Atrophy Gyrate Atrophy of the Choroid and Retina General Discussion ** REMINDER ** The information contained in the Rare Disease Database is provided for educational purposes only. It should not be used for diagnostic or treatment purposes. If you wish to obtain more information about this disorder, please contact your personal physician and/or the agencies listed in the "Resources" section of this report. Choroideremia is a genetic vision disorder which usually affects males. Female carriers may have mild symptoms without loss of vision. Major symptoms include a progressive loss of the central field of vision and night blindness during childhood. Symptoms Choroideremia is characterized by extensive defects in the pigmented surface layer of cells (epithelium) in the eye. This disorder usually begins during childhood with wasting (atrophy) of the retinal layers and choroid of the eye. The retina is the light-sensitive, internal coat of the inside of the eyeball consisting of eight layers. Seven of these layers contain nerves, and one layer contains pigmentation. The choroid is a vascular membrane located between the retina inside the eye and the "white" section on the outside the eye (sclera). The choroid contains large branched pigment cells and prevents the passage of light rays through areas of the eye outside of the pupils. Night blindness is usually the first noticeable symptom, usually occurring during childhood. Degeneration of the vessels of the choroid and functional damage to the retina occur later in life and usually lead to progressive central vision field loss and eventual blindness. Tiny bony-like tissue formations and scattered pigment clumps tend to accumulate in the middle and on the edges of the choroid. The symptoms of Choroideremia may vary greatly between affected individuals. Female carriers usually have very mild symptoms without vision loss. Causes Choroideremia is inherited as an X-linked trait. (Human traits including the classic genetic diseases, are the product of the interaction of two genes for that condition, one received from the father and one from the mother. X- linked recessive disorders are conditions which are coded on the X chromosome. Females have two X chromosomes, but males have one X chromosome and one Y chromosome. Therefore in females, disease traits on the X chromosome can be masked by the normal gene on the other X chromosome. Since males have only one X chromosome, if they inherit a gene for a disease present on the X, it will be expressed. Men with X-linked disorders transmit the gene to all their daughters, who are carriers, but never to their sons. Women who are carriers of an X-linked disorder have a fifty percent risk of transmitting the carrier condition to their daughters, and a fifty percent risk of transmitting the disease to their sons.) In 1991 Dr. Fran Cremers of the University of Nijmegen in the Netherlands isolated the gene believed to be responsible for Choroideremia. This discovery will hopefully lead to a prenatal test for the disease. Affected Population Choroideremia usually affects males while females may be carriers of the chromosome defect. However, a small number of females with the more severe form of the disorder have been identified. In the Salla area of northern Finland an unusually high concentration of cases has occurred, affecting approximately one in forty persons. Related Disorders Symptoms of the following disorders can be similar to those of Choroideremia. Comparisons may be useful for a differential diagnosis: X-linked Retinitis Pigmentosa (RP) is one of a group of inherited vision disorders causing degeneration of the retina. When the retina degenerates, as in RP, the vision decreases and may occasionally be lost. Retinitis Pigmentosa may be associated with other conditions or illnesses. The X- linked form of RP is passed from a mother (who is a carrier) to a son. The early symptoms include night blindness. This is followed by "tunnel vision" (loss of peripheral vision). The rate and extent of progression of symptoms is extremely variable. (For more information on this disorder, choose "Retinitis Pigmentosa" as your search term in the Rare Disease Database). Diffuse Choriocapillaris Atrophy is characterized by degeneration of the internal cell layer of the choroid of the eye. The choroid is a vascular membrane located between the retina inside the eye and the "white" membrane outside the eye (sclera), which contains large branched pigment cells and prevents the passage of light rays through areas outside of the pupil. Gyrate Atrophy of the Choroid and Retina is characterized by a circular- patterned degeneration in the choroid and retina of the eye. Therapies: Standard 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. Therapies: Investigational Studies of families with Choroideremia are underway to determine the exact location of the gene responsible for the disorder. When the location is discovered, the exact mechanism whereby this progressive loss of vision develops may become better understood, and new treatments may eventually be found. This disease entry is based upon medical information available through May 1991. 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. Resources For more information on Chorodieremia, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 NIH/National Eye Institute (NEI) 9000 Rockville Pike Bethesda, MD 20892 (301) 496-5248 Eye Research Institute of Retina Foundation Macular Disease Research Center 20 Staniford St. Boston, MA 02114 (617) 742-3140 National Federation of the Blind 1800 Johnson Street Baltimore, MD 21230 (301) 659-9314 1-800-638-7518 American Council of the Blind, Inc. (ACB) 1155 - 15th St., NW, Suite 720 Washington, D.C. 20005 (202) 467-5081 (800) 424-8666 American Foundation for the Blind (AFB) 15 W. 16th St. New York, NY 10011 (212) 620-2000 Regional offices: Atlanta, GA (404) 525-2303 Chicago, IL (312) 245-9961 Dallas, TX (214) 352-7222 San Francisco, CA (415) 392-4845 Vision Foundation, Inc. 818 Mt. Auburn Street Watertown, MA 02172 (617) 926-4232 1-800-852-3029 (Inside Massachusetts) Council of Families with Visual Impairment 6212 W. Franklin Street Richmond, VA 23226 (804)288-0395 National Association for Parents of the Visually Impaired, Inc. (NAVPI) P.O. Box 180806 Austin, TX 78718 (512) 459-6651 National Association for the Visually Handicapped (NAVH) 305 East 24th Street New York, NY 10010 (212) 889-3141 or 3201 Balboa Street San Francisco, CA 94121 (414) 221-3201 National Library Service for the Blind and Physically Handicapped Library of Congress 1291 Taylor Street NW Washington, DC 20542 (202) 287-5100 For genetic information and genetic counseling referrals, please contact: March of Dimes Birth Defects Foundation 1275 Mamaroneck Avenue White Plains, NY 10605 (914) 428-7100 Alliance of Genetic Support Groups 35 Wisconsin Circle, Suite 440 Chevy Chase, MD 20815 (800) 336-GENE (301) 652-5553 References This Rare Disease Database entry is based upon outlines prepared by medical and dental students (1984-1986) at the Medical College of Virginia for their course in human genetics, and the following articles: MENDELIAN INHERITANCE IN MAN, 7th ed.: Victor A. McKusick; Johns Hopkins University Press, 1986. Pp. 1336. MULTIPOINT LINKAGE ANALYSIS OF LOCI IN THE PROXIMAL LONG ARM OF THE HUMAN X CHROMOSOME: APPLICATION OF MAPPING THE CHOROIDEREMIA LOCUS: J.G. Lesko, et al.; Am J Hum Genet (April 1987, issue 40(4)). Pp. 303-311. CHOROIDEREMIA-LOCUS MAPS BETWEEN DXS3 AND DXS11 ON Xq: A. Gal, et al.; Hum Genet (June 1986, issue 73(2)). Pp. 123-126. HISTOPATHOLOGIC OBSERVATIONS IN CHOROIDEREMIA WITH EMPHASIS ON VASCULAR CHANGES OF THE UVEAL TRACT: J.D. Cameron, et al.; Ophthalmology (February 1987, issue 94(2)). Pp. 187-196.