Aniridia 2
Patient Information
Characteristics
Background and History
Aniridia was first reported in the last century. The term applies to a lack of iris which is the colored part of the eye and forms the pupil. Most patients do not have a complete absence of iris but rather some degree of underdevelopment. The presentation is highly variable and there are usually other physical signs in the eye such as cataracts, abnormal pigmentation of the retina, and anomalies of the drainage of fluids that often lead to glaucoma.
Clinical Correlations
Abnormal development of the iris is usually apparent by direct visualization. In some patients the defects are subtle and a more detailed examination by an ophthalmologist is necessary. Cataracts may be present. The retina may be abnormally pigmented and rarely the optic nerve is damaged as well. Only a few families have been reported and the clinical findings are inconsistent.
No consistent abnormalities outside of the eye have been reported.
Genetics
Inheritance
Most reported families have a pattern of transmission that is consistent with autosomal dominant inheritance. Affected parents pass the genetic defect to their children with a 50% probability. However, many patients with aniridia do not have a family history of the condition.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission
Diagnosis and Prognosis
The diagnosis will most likely be made by an ophthalmologist. Aniridia is present at birth but if the family history is negative and the iris defect is minor the diagnosis may not be made until adulthood. Glaucoma can occur at any time and patients need to be monitored throughout life. Rigorous treatment may be required. Cataracts may also not be detected until sometime after birth and can be surgically removed if they are dense enough to cause vision problems.
Since tumors of the kidney sometimes occur, periodic evaluation of the urinary tract should also be done.
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