Granular Corneal Dystrophy

Updated: Sep 22, 2014
  • Author: Natalie A Afshari, MD, MA, FACS; Chief Editor: Hampton Roy, Sr, MD  more...
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Overview

Background

Granular corneal dystrophy (GCD), an IC3D category 1 dystrophy, is an autosomal-dominant, bilateral, noninflammatory condition that results in deposition of discrete, irregularly shaped opacities in the cornea by adulthood. It specifically affects the middle portion of the cornea (stroma) and can eventually cause decreased vision and eye discomfort.

There are two clinically separate types: granular corneal dystrophy type I (classic type) and granular corneal dystrophy type II (Avellino corneal dystrophy), which tends to have fewer corneal deposits, potentially resembling a combination of lattice corneal dystrophy and granular corneal dystrophy. 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 Reid 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.
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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 layer, (2) stromal corneal dystrophies affect the central layer of cornea (the stroma), and (3) posterior corneal dystrophies involve the Descemet membrane and the endothelium. Granular corneal dystrophy is a stromal dystrophy, but the epithelium and Bowman layer may be affected in late disease.

The age of onset for most corneal dystrophies is before 20 years (exceptions include map-dot-fingerprint dystrophy and Fuchs corneal dystrophy). Most corneal dystrophies are inherited in a dominant pattern. Exceptions include macular corneal dystrophy, type-3 lattice dystrophy, and the autosomal-recessive form of congenital hereditary endothelial dystrophy.

Granular corneal dystrophy types I and II result from mutations in the TGFBI (BIGH3) gene. [1, 2] Depending on the specific mutation in the TGFBI gene, phenotypes of corneal dystrophy may differ. [3, 4]

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Epidemiology

Frequency

United States

Although granular corneal dystrophy type II is more common than granular corneal dystrophy type I in the United States, both are rare.

International

Granular corneal dystrophy is uncommon worldwide. Granular corneal dystrophy type I is more common in Europe, while granular corneal dystrophy type II is more prevalent in Japan, Korea, and the United States. [5]

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

In granular corneal dystrophy type I, corneal changes appear within the first decade of life but may not be visible until the second decade of life. [5] Visual acuity usually remains good until the fourth or fifth decade of life, once the opacities become confluent. Granular corneal dystrophy type II is usually diagnosed during early adulthood. [2]

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