Excerpt from Dystrophy, Granular

Synonyms, Key Words, and Related Terms: granular dystrophy, corneal dystrophy, granular corneal dystrophy

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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).

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. Depending on the specific mutation in the beta ig-h3 gene, the phenotypes of corneal dystrophy may differ.

Frequency:

In the US: Uncommon

Internationally: Uncommon

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.