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Granular corneal dystrophy type II
Type II granular corneal dystrophy (GCDII) is a rare form of stromal corneal dystrophy (see this term) characterized by irregular-shaped well-demarcated granular deposits in the superficial central corneal stroma, and progressive visual impairment.
Prevalence of this form of corneal dystrophy is not known. GCDII appears to be more prevalent in Japan, Korea and the USA.
Lesions appear within the first decade of life and may be evident by 3 years of age. Onset is generally earlier in homozygous patients. Pain may accompany mild corneal erosions. Visual acuity usually remains good until late in the course of the condition. The course is slowly progressive but homozygotes may demonstrate more rapid progression.
GCDII is caused by a p. Arg124His mutation in the TGFBI gene (5q31).
Opacities are initially small superficial whitish dots. Subsequently, ring or stellate-shaped stromal opacities develop. Final-stage opacities are more superficial and translucent, and may coalesce in the anterior stroma.
Deposits are less numerous than in type I granular corneal dystrophy, and are sometimes lattice-like linear deposits and may superficially resemble lattice corneal dystrophy (see these terms). The features of GCD may be very similar to the corneal features of monoclonal gammopathies (see these terms).
Both forms of GCD usually follow an autosomal dominant pattern of inheritance, but sporadic de novo mutations have been reported.
Management and treatment
A penetrating keratoplasty is usually indicated, but superficial stromal opacities can sometimes be ablated without the removal of the entire cornea.