Aniridia in the Newborn
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In 1818, Barratta first described aniridia (Greek for absence of the iris). Aniridia is a rare, bilateral, panophthalmic disorder, of which iris hypoplasia is the most striking feature (see image below).
Aniridia also has corneal, lens, optic nerve, and retinal manifestations. Foveal and optic nerve hypoplasia are often present, causing a reduction in visual acuity and congenital sensory nystagmus. Progressive worsening of vision may occur later in life as a result of cataracts, glaucoma, and corneal opacification. [1]
Aniridia may be familial or sporadic. It is caused by a mutation in the PAX6 gene on chromosome 11. [2]
Approximately 85% of cases are familial (designated AN1) with autosomal dominant inheritance with complete penetrance but variable expressivity. These familial cases usually have isolated ocular involvement.
The 15% of cases that are sporadic have a deletion or mutation on the short arm of chromosome 11. The same deletion is responsible for the development of Wilms tumor (nephroblastoma).
The exact pathogenesis of aniridia is unknown. After early reports of ocular colobomas in patients with aniridia, some authors proposed that it is a colobomatous disorder. Others attributed it to a failure of mesodermal development with involvement of the rim of the optic cup, causing iris hypoplasia. Still others advocated the neuroectodermal theory, which links the presence of retinal anomalies and iris muscular hypoplasia to a developmental failure of neuroectoderm.
United States
Aniridia is a very rare disorder. According to a population-based study in Michigan, it has been estimated to affect approximately 1 per 61,000 newborns.
International
A more recent study from Denmark reported the incidence as 1 per 96,000 live births.
Aniridia itself is not a lethal disorder. However, miscarriages and a stillborn child have been the only results of a consanguineous mating between individuals with aniridia. A homozygous mutation of the aniridia gene may possibly be lethal. The morbidity of aniridia is significant because of the decreased vision and nystagmus.
No racial predilection has been described.
The incidence of aniridia is equal in males and females.
Aniridia is a congenital disorder apparent at birth. It is never acquired.
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Sophie Bakri, MD Assistant Professor of Ophthalmology, Vitreoretinal Diseases and Surgery, Mayo Clinic of Rochester
Sophie Bakri, MD is a member of the following medical societies: American Academy of Ophthalmology
Disclosure: Nothing to disclose.
John W Simon, MD
John W Simon, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
J James Rowsey, MD Former Director of Corneal Services, St Luke’s Cataract and Laser Institute
J James Rowsey, MD is a member of the following medical societies: American Academy of Ophthalmology, American Association for the Advancement of Science, American Medical Association, Association for Research in Vision and Ophthalmology, Florida Medical Association, Sigma Xi, Southern Medical Association, Pan-American Association of Ophthalmology
Disclosure: Nothing to disclose.
Donny W Suh, MD, FAAP Chief of Pediatric Ophthalmology and Strabismus, Children’s Hospital and Medical Center; Associate Professor, Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center
Donny W Suh, MD, FAAP is a member of the following medical societies: American Academy of Ophthalmology, American Academy of Pediatrics, American Association for Pediatric Ophthalmology and Strabismus, American Medical Association, Iowa Medical Society, National Eye Care Project
Disclosure: Received research grant from: NIH.
Gerhard W Cibis, MD Clinical Professor, Director of Pediatric Ophthalmology Service, Department of Ophthalmology, University of Kansas School of Medicine
Gerhard W Cibis, MD is a member of the following medical societies: American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus, American Ophthalmological Society
Disclosure: Nothing to disclose.
Aniridia in the Newborn
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