$Unique_ID{BRK03471} $Pretitle{} $Title{Aniridia} $Subject{Aniridia Irideremia Disorder Aniridia Type I (AN1) Aniridia Type II (AN2) Aniridia associated with mental retardation WAGR Syndrome (Wilms Tumor-Aniridia-Gonadoblastoma-Mental Retardation) Iridogoniodysgenesis Rieger Syndrome Hereditary Juvenile Glaucoma} $Volume{} $Log{} Copyright (C) 1988, 1989 National Organization for Rare Disorders, Inc. 524: Aniridia ** IMPORTANT ** It is possible the main title of the article (Aniridia) 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 Irideremia Disorder Subdivisions: Aniridia Type I (AN1) Aniridia Type II (AN2) Aniridia associated with mental retardation WAGR Syndrome (Wilms Tumor-Aniridia-Gonadoblastoma-Mental Retardation) Information on the following diseases can be found in the Related Disorders section of this report: Iridogoniodysgenesis Rieger Syndrome itary Juvenile Glaucoma General Discussion Aniridia is a genetic vision disorder characterized by lack of normal development of the eye's iris. The iris is the circular colored membrane in the middle of the eyeball. It is perforated in the center by an opening known as the pupil, which regulates the amount of light that enters the eye. Aniridia is characterized by partial or complete absence of the iris. Four forms of Aniridia have been identified to date. Each can be distinguished by accompanying symptoms. Some cases are thought to occur sporadically, although a chromosome defect is the cause of most forms of this disorder. Symptoms Aniridia is marked by partial or complete absence of the eye's iris. Vision is preserved in some mild cases of Aniridia. The iris fails to develop normally before birth in one or both eyes. At least four types of Aniridia are thought to exist. One type is marked by incomplete expression of the disorder. Some people with this type of Aniridia may be unaware of the eye problems because pupils appear normal and usually only one eye is affected with thinning of the iris. In a second type of Aniridia, iris abnormalities may occur alone, or in combination with other disorders. Accompanying disorders may include cataracts (clouding of the crystalline lens of the eye), glaucoma (gradual loss of vision due to increased pressure inside the eyeball which may be accompanied by varying degrees of pain), or superficial clouding of the cornea (corneal pannus). Rapid involuntary movement of the eyeball (nystagmus), and underdevelopment of the fovea area of the retina (which controls acute vision) may also occur. A third type of Aniridia is associated with mental retardation, and a fourth type occurs in conjunction with Wilms' Tumor, genitourinary abnormalities, and possible mental retardation. (For more information on Wilms' Tumor, please choose "Wilm" as your search term in the Rare Disease Database.) Causes More than one cause of Aniridia is thought to exist. Type 1 Aniridia (AN1) involves a defect of chromosome 2, and is thought to be inherited as an autosomal recessive trait. All Aniridia cases caused by chromosome 2 abnormalities have been identified in one lineage. Defects on chromosome 11, 13 and/or 22 are thought to cause Aniridia 2 (AN2). AN2 is thought to be inherited as an autosomal dominant trait, although some cases appear to be spontaneous genetic mutations. A third type of Aniridia associated with mental retardation, and a fourth type occurring in conjunction with Wilms' Tumor are also thought to be inherited as autosomal dominant traits. 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. In recessive disorders, the condition does not appear unless a person inherits the same defective gene from each parent. If one receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will show no symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is twenty-five percent. Fifty percent of their children will be carriers, but healthy as described above. Twenty-five percent of their children will receive both normal genes, one from each parent and will be genetically normal. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the normal gene and resulting in appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child. Affected Population All types of Aniridia affect males and females in equal numbers. This disorder is thought to occur in approximately one in 100,000 to 200,000 live births in the United States. Related Disorders Symptoms of the following disorders can be similar to those of Aniridia. Comparisons may be useful for a differential diagnosis: Iridogoniodysgenesis is a genetic eye structure disorder present at birth. It is characterized by underdevelopment of the foundation substance (stroma) of the iris. Glaucoma also occurs followed by the iris changing to a lighter color. Glaucoma is a vision disorder marked by gradual loss of vision, and increased pressure inside the eyeball possibly accompanied by varying degrees of pain. Rieger Syndrome, also known as Iridogonodysgenesis with somatic anomalies, is characterized by defective embryonic development of the middle layer of the cornea and iris sections of the eye. This is accompanied by abnormalities in the pupil, which is the opening that regulates the amount of light entering the eyeball. The edges of the cornea are clouded at birth and glaucoma also occurs. Hereditary Juvenile Glaucoma is a genetic vision disorder which may be present at birth. However, onset of symptoms may occur later in childhood or adolescence. Other cases may represent an early onset of some other forms of glaucoma. Glaucoma is characterized by diminished clear vision accompanied by increased pressure with possible pain inside the eyeball in various degrees. Therapies: Standard Treatment of Aniridia is usually directed at improving clear vision. Drugs or surgery may be helpful for glaucoma and/or cataracts. Contact lenses may be beneficial in some cases. When a genetic cause cannot be identified, patients should be evaluated for the possibility of the development of Wilms' Tumor. (For more information on this disorder, please choose "Wilm" as your search term in the Rare Disease Database.) Services which benefit vision impaired or mentally retarded individuals and their families may be of assistance in some cases. Genetic counseling is recommended. Other treatment is symptomatic and supportive. Therapies: Investigational This disease entry is based upon medical information available through June 1988. 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 Aniridia, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 NIH/National Eye Institute 9000 Rockville Pike Bethesda, MD 20892 (301) 496-5248 Eye Research Institute of Retina Foundation 20 Staniford Street Boston, MA 02114 (617) 742-3140 Vision Foundation, Inc. 818 Mt. Auburn Street Watertown, MA 02172 (617) 926-4232 National Association for Parents of the Visually Impaired, Inc. P.O. Box 180806 Austin, TX 78718 (512) 459-6651 National Association for the Visually Handicapped 22 W. 21st Street, Sixth Floor New York, NY 10010 (212) 889-3141 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 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. 55-56. WILMS' TUMOR DETECTION IN PATIENTS WITH SPORADIC ANIRIDIA. SUCCESSFUL USE OF ULTRASOUND: A.L. Friedman; Am J Dis Child (February 1986, issue 140 (2)). Pp. 173-174. FAMILIAL ISOLATED ANIRIDIA ASSOCIATED WITH A TRANSLOCATION INVOLVING CHROMOSOMES 11 AND 22 [t (11;22) (p13;q12.2)]: J.W. Moore, et al.; Hum Genet (April 1986, issue 72 (4)). Pp. 297-302. WILMS' TUMOR WITH ANIRIDIA/IRIS DYSPLASIA AND APPARENTLY NORMAL CHROMOSOMES: V.M. Riccardi, et al.; J Pediatr (April 1982, issue 100 (4)). Pp. 574-577. AUTOSOMAL DOMINANT ANIRIDIA: PROBABLE LINKAGE TO ACID PHOSPHATASE LOCUS ON CHROMOSOME 2: R.E. Ferrell, et al.; Proc Natl Acad Sci USA (March 1980, issue 77 (3)). Pp. 1580-1582.