CD-ROM Today 1996 January/CD-ROM Today 1996 January.iso/dp/0347/03471.txt

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$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}
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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
     [phone]

     NIH/National Eye Institute
     9000 Rockville Pike
     Bethesda, MD  20892
     [phone]

     Eye Research Institute of Retina Foundation
     20 Staniford Street
     Boston, MA  02114
     [phone]

     Vision Foundation, Inc.
     818 Mt. Auburn Street
     Watertown, MA 02172
     [phone]

     National Association for Parents of the Visually Impaired, Inc.
     P.O. Box 180806
     Austin, TX  78718
     [phone]

     National Association for the Visually Handicapped
     22 W. 21st Street, Sixth Floor
     New York, NY  10010
     [phone]

For genetic information and genetic counseling referrals, please contact:

     March of Dimes Birth Defects Foundation
     1275 Mamaroneck Avenue
     White Plains, NY  10605
     [phone]

     Alliance of Genetic Support Groups
     35 Wisconsin Circle, Suite 440
     Chevy Chase, MD  20815
     (800) 336-GENE
     [phone]

For genetic information and genetic counseling referrals, please contact:

     March of Dimes Birth Defects Foundation
     1275 Mamaroneck Avenue
     White Plains, NY  10605
     [phone]

     Alliance of Genetic Support Groups
     35 Wisconsin Circle, Suite 440
     Chevy Chase, MD  20815
     (800) 336-GENE
     [phone]

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.