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Granular corneal dystrophy
Granular corneal dystrophy (Courtesy of Michael Belin, MD)
Granular corneal dystrophy
Granular corneal dystrophy (Courtesy of Michael Belin, MD)
Granular dystrophy of the cornea
Cornea with granular dystrophy
Mutations in the TGFBI gene lead to deposition of abnormal protein clumps (amyloid) in the cornea
Mutations in the TGFBI gene lead to deposition of abnormal protein clumps (amyloid) in the cornea

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.

Treatment Options

Penetrating keratoplasty can be temporarily helpful in restoring vision but recurrence is common.  Various forms of laser refractive surgery are probably contraindicated as some patients with initially clear corneas have developed typical granular opacities.

References

Sakimoto T. Granular corneal dystrophy type 2 is associated with morphological abnormalities of meibomian glands. Br J Ophthalmol. 2014 Jul 17.  [Epub ahead of print].

PubMed ID: 
250334048

Han KE, Chung WS, Kim T, Kim KS, Kim TI, Kim EK. Changes of Clinical Manifestation of Granular Corneal Deposits Because of Recurrent Corneal Erosion in Granular Corneal Dystrophy Types 1 and 2. Cornea. 2012 Nov 5. [Epub ahead of print]

PubMed ID: 
23132456

Stone EM, Mathers WD, Rosenwasser GO, Holland EJ, Folberg R, Krachmer JH, Nichols BE, Gorevic PD, Taylor CM, Streb LM, et al. Three autosomal dominant corneal dystrophies map to chromosome 5q. Nat Genet. 1994 Jan;6(1):47-51.

PubMed ID: 
8136834

Dinh R, Rapuano CJ, Cohen EJ, Laibson PR. Recurrence of corneal dystrophy after excimer laser phototherapeutic keratectomy. Ophthalmology. 1999 Aug;106(8):1490-7.

PubMed ID: 
10442892