Aniridie
Aniridia refers to either the clinical sign of a complete/partial absence of the iris, or more specifically to the disease entity classic aniridia. Rarely other genetic conditions may cause this sign.
Epidemiology
Classic aniridia is inherited as an autosomal dominant condition and is seen in ~1 in 50,000 births according to population studies .
Clinical presentation
Classic aniridia tends to be bilateral and usually presents with other ocular abnormalities including foveal (+/-optic nerve) hypoplasia; affected patients are at risk of developing cataracts, glaucoma and/or ptosis.
Although classically a distinction is made between a partial or a complete aniridia, in practice the distinction is usually academic, as on formal testing with gonioscopy - a technique to examine the iridocorneal angle - a small iris stump can always be demonstrated.
Pathology
Etiology
- classic aniridia
- Gillespie syndrome: triad of partial aniridia, ataxia and learning disability
- WAGR syndrome
- multisystemic smooth muscle dysfunction syndrome
Genetics
Classic aniridia is found with various PAX6 loss-of-function mutations . Other genetic loci that have been implicated include FOXC1, PITX2, and/or associated regulatory sequences. Gillespie syndrome is associated with mutations of the ITPR1 gene . Multisystemic smooth muscle dysfunction syndrome is related to ACTA2 mutations. WAGR syndrome has been linked to PAX6 and WT1 deletions on chromosome 11p.
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