Background
Granular dystrophy is an autosomal dominant, bilateral, noninflammatory condition that results in deposition of opacities in the cornea by adulthood. It specifically affects the middle portion of the cornea (stroma) and eventually can cause decreased vision and eye discomfort. Severe cases of granular dystrophy can be treated with either excimer laser ablation or by replacing cornea (corneal transplant). An example is shown in the image below.
Granular dystrophy. Image courtesy of James J Reidy, MD, FACS, Associate Professor of Ophthalmology, State University of New York, School of Medicine & Biomedical Sciences, Buffalo, New York. Pathophysiology
The cornea is the clear outer coat of the front of eye. A dystrophy of the cornea is defined as a bilateral noninflammatory clouding of cornea. Corneal dystrophies can be divided into 3 categories based on their location within the cornea, as follows: (1) anterior corneal dystrophies affect the corneal epithelium and may involve the Bowman membrane; (2) stromal corneal dystrophies (which include granular dystrophy) affect the central layer of cornea, the stroma; and (3) posterior corneal dystrophies involve the Descemet membrane and endothelium.
Most corneal dystrophies have an onset prior to age 20 years (exceptions include map-dot-fingerprint dystrophy and Fuchs corneal dystrophy). Most corneal dystrophies are dominantly inherited, exceptions being macular dystrophy, type-3 lattice dystrophy, and the autosomal recessive form of congenital hereditary endothelial dystrophy.
Granular corneal dystrophy types I, II (Avellino dystrophy), have been reported to result from mutations in the BIGH3 gene.[1] Depending on the specific mutation in the beta ig-h3 gene, the phenotypes of corneal dystrophy may differ.
Epidemiology
Frequency
United States
Granular dystrophy is uncommon in the United States.
International
Granular dystrophy is uncommon worldwide.
Mortality/Morbidity
Corneal changes generally first become visible during the second decade of life, but vision may not be affected until the fourth to fifth decade of life. Eye pain from recurrent corneal erosions also can occur.
Sex
No sexual predilection has been reported.
Age
Corneal changes usually become visible during the second decade of life, but patients may not be affected until the fourth to fifth decade of life.
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Mori H, Miura M, Iwasaki T, et al. Three-dimensional optical coherence tomography-guided phototherapeutic keratectomy for granular corneal dystrophy. Cornea. Sep 2009;28(8):944-7. [Medline].
Dalton K, Schneider S, Sorbara L, Jones L. Confocal microscopy and optical coherence tomography imaging of hereditary granular dystrophy. Cont Lens Anterior Eye. Nov 27 2009;[Medline].
Das S, Langenbucher A, Seitz B. Excimer laser phototherapeutic keratectomy for granular and lattice corneal dystrophy: a comparative study. J Refract Surg. Nov-Dec 2005;21(6):727-31. [Medline].
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Klintworth GK. Advances in the molecular genetics of corneal dystrophies. Am J Ophthalmol. Dec 1999;128(6):747-54. [Medline].
Krachmer J. Cornea. Vol 2. 1996.
Yamamoto S, Okada M, Tsujikawa M, et al. The spectrum of beta ig-h3 gene mutations in Japanese patients with corneal dystrophy. Cornea. May 2000;19(3 Suppl):S21-3. [Medline].
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