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This is a systemic amyloidosis disorder with significant corneal disease. The corneal stroma contains linear deposits which are more discrete, more peripheral, more delicate, and more radial than those in lattice type I with which it is sometimes confused. There is also less accumulation of amorphous amyloid material than in type I. The onset is often later as well, and rarely seen in childhood. Corneal sensitivity is reduced. Vision is less affected than in type I lattice dystrophy and patients rarely require keratoplasty, and, if so, later in life.
Amyloid deposits are found in the cornea, sclera, choroid, lacrimal gland, ciliary nerves, and adnexal blood vessels. Ptosis and extraocular muscle dysfunction is not significant.
Amyloid deposits are found throughout the body including blood vessels, heart, kidney, skin and nerves. A “mask-like” facies with a protruding lower lip, dry itchy skin, peripheral and cranial neuropathy, and renal failure are clinical features but often have their onset late in life. Facial paralysis and bulbar palsy may be the result.
While this is considered an autosomal dominant disorder, presumed homozygous cases have been reported in Finland where the first cases were described. These cases seem to have more severe disease with an earlier onset than found among patients with heterozygous mutations. Mutations in the GSN gene located at 9q34 are responsible.
Penetrating keratoplasty can be beneficial but is rarely needed for visual rehabilitation. The amyloid deposits may recur in the donor tissue. The reduced corneal sensitivity secondary to neural involvement increases the risk of post-operative neurotrophic epithelial defects.