hyaline degeneration

Corneal Dystrophy, Lattice Type I

Clinical Characteristics
Ocular Features: 

Lattice corneal dystrophy type I is one of the more common corneal dystrophies and occurs throughout the world.  Randomly oriented linear opacities resembling cotton threads accumulate in the central portions of the stroma.  These usually become apparent in the first decade of life although they are sometimes seen in infancy.  The peripheral cornea is relatively spared and intervening stromal areas are clear.  This is a progressive disorder in which vision during childhood is often normal but by the fifth and sixth decades most patients have severe visual impairment due to increasing accumulations of amyloid.  Corneal erosions may occur in the absence of stromal infiltrates.

Systemic Features: 

No systemic disease is found in LCD1 (as opposed to LCD type II).

Genetics

Type I lattice dystrophy is an autosomal dominant disorder as the result of mutations in the TGFBI gene (5q31).  Other corneal dystrophies (granular I or Groenouw type I, combined granular/lattice or Avellino type, Thiel-Behnke, Reis-Bucklers, epithelial basement membrane disease) have mutations in the same region of the same gene casting doubt on the value of using solely clinical and histologic distinctions in current classifications of these corneal disorders.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Recurrent corneal erosions benefit from standard treatments while penetrating keratoplasty may be necessary by the fifth decade to improve acuity.

References
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Corneal Dystrophy, Granular

Clinical Characteristics
Ocular Features: 

The corneal opacities in this disorder are usually located in the anterior stroma of the central cornea, and consist of discrete grayish-white, irregular granules with sharp margins.  The peripheral cornea and areas between the opacities remain clear.  The opacities may be apparent in the first decade but vision remains good throughout childhood.  The epithelial surface is usually smooth in children but adults can develop irregularities.  As the opacities enlarge and grow in number the cornea becomes increasingly opaque and older patients experience considerable loss of vision.  There is some variation in the number of opacities among individuals and considerable clinical heterogeneity occurs both within and between families.  The histologic appearance of the corneal deposits are said to be characteristic with eosinophilic deposits in the anterior stroma secondary to accumulations of mutant transforming growth factor beta induced protein.

The number and morphology of the granular deposits change throughout life, influenced to some extent by episodes of recurrent corneal erosions and age of patients.  Deposits become more annular and lattice-like in morphology, especially in the third decade and become more discoid by the fifth decade. 

It has been reported that the morphology and function of the meibomian glands are altered in this disease as well.

Systemic Features: 

No associated systemic disease has been described.

Genetics

This is another autosomal dominant corneal dystrophy resulting from mutations in the TGFBI gene (5q31) (others being Reis-Bucklers, Thiel-Behnke, lattice types I and IIIA, epithelial basement membrane disease, and Avellino). These are therefore allelic disorders of the same mutant gene.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Penetrating keratoplasty can be temporarily helpful in restoring vision but recurrence is common.  Opacities may also occur following the application of various types of refractive surgery (even in initially clear corneas).

References
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