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Corneal Dystrophy, Avellino Type
There is little to support the designation of a corneal dystrophy as ‘Avellino type’ but it is included in this database because it is entrenched in the literature. It has features of both lattice dystrophy, type I, and granular dystrophy type I, which might be expected since all of these result from mutations in the same gene, TGFBI on chromosome 5. Not surprisingly, reported cases have clinical and histological features of both lattice and granular dystrophy and hence are labeled as having combined granular-lattice corneal dystrophy. There is considerable variation of the nature and quantity of the stromal deposits both within and among families, a common characteristic of autosomal dominant disorders. Even though clinical evidence may suggest primarily lattice or granular dystrophy, histological studies can reveal changes characteristic of both.
Early cases could be traced to the Avellino region of Italy from which the title was derived but more recent reports have described families from around the world.
No systemic disease is associated with this disorder.
Mutations in the TGFBI (5q31) have been found in this so-called combined dystrophy. Autosomal dominant transmission is evident from familial cases. Mutations in the same gene also cause Thiel-Behnke (602082), Reis-B√ºcklers (608470), granular (Groenouw) type I (121900), lattice type I (122200) and epithelial basement membrane dystrophy (121820). The combined features of lattice and granular dystrophies in the same corneas resulting from mutations in the same gene calls into question the value of relying solely on clinical and histological evidence to classify disease. Modern genotyping now enables greater accuracy in the nosology and already the Cornea Society has incorporated this information in its recent reclassification of these dystrophies (Cornea Society IC3D Corneal Dystrophies©).
Penetrating keratoplasty can improve vision at least temporarily but deposits tend to recur. LASIK has been reported to exacerbate the number and density of the opacities. Patients treated with PRK may do better and can retain corneal clarity for a decade or more.