INHERITANCE PATTERN
AD
VISUAL ACUITY
Visual acuity is normal or only impaired in the 40s, although they may experience glare and photophobia.
CORNEA
GCD-1: small, Gray-white opacities resembling breadcrumbs or snowflakes in the superficial cornea, separated by clear spaces in the anterior stroma. With progression, the lesions may coalesce to form larger deposits that run deeper into the stroma.
The lesions typically manifest in the central cornea and may not extend toward the limbus.
GCD-2 – Patients in childhood or early adulthood present with white dots in the central cornea, which progress to stellate-shaped opacities at a later age. These granules are fewer than that in GC1. After the initial appearance of granular deposits, deep lattice-like amyloid lesions may become visible. These amyloid lesions are more commonly observed.
FELLOW EYE:
Similar changes or corneal graft
Questions:
What are the clinical features of Granular Dystrophy?
Recurrent erosions are rare. Vision is often normal or only impaired in the 40s. Full-thickness graft is sometimes needed, but recurrence is unusual. Recurrence may sometimes be treated with EXCIMER laser.
What is the etiology of Granular corneal dystrophy?
Corneal dystrophies result from a point mutation in the TGFBI gene (also known as BIGH3), which is situated on the chromosome 5q31 locus. This gene encodes a protein called transforming growth factor beta-induced protein (TGFBIp), alternatively referred to as kerato-epithelin. The TGFBIp plays a critical role in maintaining healthy corneal tissue. When mutations occur, they can lead to various types of corneal dystrophy.
What are the types of Granular Dystrophy?
Granular corneal dystrophy type 1
(GCD1), also referred to as classic granular or Groenouw corneal dystrophy type 1, typically begins early in life with the formation of white opacities in the superficial layer of the cornea. Initially, the condition manifests as lesions interspersed with clear areas of the cornea, resembling breadcrumbs or snowflakes, which can merge over time to create larger deposits as the disease progresses. These lesions primarily develop in the central cornea and may not extend to the limbus.
Because GCD1 advances slowly, most patients maintain relatively good visual acuity until around their fifth decade of life, although they may experience glare and photophobia. Granular deposits, which may originate from the corneal epithelium or keratocytes, exhibit a bright red coloration when stained with Masson trichrome stain, indicating hyaline. Unlike GCD2 and lattice corneal dystrophy, GCD1 does not feature amyloid deposits.
Under electron microscopy, these deposits appear as rod-shaped or trapezoidal structures. However, they can contribute to recurrent corneal erosions by disrupting cells in the corneal epithelium or Bowman’s layer. This erosion often leads to sharp pain on the corneal surface, particularly upon awakening or during sleep, accompanied by symptoms such as blurred vision, tearing, redness, and photophobia.
Granular corneal dystrophy type 2
GCD type 2 (GCD2), also known as Avellino corneal dystrophy or combined granular-lattice corneal dystrophy, presents similarly to GCD1. However, GCD2 manifests in childhood or early adulthood, with white dots progressing to stellate-shaped opacities later in life. Unlike GCD1, GCD2 typically involves fewer corneal deposits. Deep lattice-like amyloid lesions appear after the initial granular deposits, which are more common. Notably, both hyaline and amyloid deposits can be present, staining positively with Masson trichome and Congo red stains, respectively. Electron microscopy reveals rod-shaped deposits and possible amyloid fibrils. These deposits can lead to recurrent corneal erosions and decreased visual acuity due to increasing corneal opacity in later stages of the disease.
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