![]() These deposits may cause recurrent corneal erosions due to breakdown of cells on the corneal epithelial layer or Bowman’s layer. Electron microscopy reveals rod shaped or trapezoidal deposits. Amyloid is not present, differentiating it from GCD2 and lattice corneal dystrophy. Granular deposits, which may derive from corneal epithelium or keratocytes, stain positive as bright red for hyaline using the Masson trichrome stain. Because GCD1 is a slowly progressive condition, most patients can experience glare and photophobia but can typically maintain good visual acuity until the fifth decade of life. Lesions appear in the central cornea and may not extend to the limbus. The disease initially appears as lesions separated by spaces of clear cornea, resembling breadcrumbs or snowflakes, and can coalesce to form larger deposits with disease progression. The onset of GCD1 occurs early in life with development of white opacities in the superficial cornea. GCD Type 1 (GCD1) is also known as classic granular or Groenouw corneal dystrophy type 1. Granular corneal dystrophy is categorized into two subtypes: Granular corneal dystrophy is a part of a group of epithelial-stromal TGFBI dystrophies, but the epithelium and Bowman layer may be affected in late disease. Granular dystrophy is less prevalent in the US, occurring in an estimated 1% or less of the population. It is currently the most common type of TGFBI corneal dystrophy in certain countries in Asia, specifically Korea and Japan. However, studies have demonstrated that it has been seen in populations without Italian ancestry. GCD type 2 was first described from the first four patients in the original study, each tracing their ancestry from the Italian province of Avellino. GCD type 1 is reportedly more prevalent in Europe. Homozygote individuals tend to have more severe phenotype with larger and confluent corneal opacities than heterozygotes. Risk Factorsĭue to autosomal dominant inheritance, positive family history increases the risk of GCD. This gene encodes transforming growth factor beta induced protein (TGFBIp), also known as the protein kerato-epithelin. It is caused by a point mutation in the transforming growth factor β induced (TGFBI) gene located on chromosome 5q31 locus, also known as BIGH3. GCD is inherited in an autosomal dominant pattern. There are two types of GCD, which are distinguished by their clinical appearance and composition of corneal deposits. As this condition progresses, the bilateral granules increase in size and number but do not extend to the peripheral limbus. These opacities typically present in the first decade of life, as early as 3 years of age. Granular corneal dystrophy (GCD) is a rare, inherited condition characterized by granular deposits in the stromal layer of the cornea, leading to slow progression of visual impairment due to loss of corneal transparency.
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