Aqueous outflow system in familial amyloidotic polyneuropathy, Portuguese type

Familial amyloidotic polyneuropathy (FAP) is a hereditary disease which may present a wide range of ocular manifestations. Glaucoma is amongst the most serious complications of FAP. We report the results of ultrastructural study of the trabecular meshwork in a glaucomatous patient with the Portuguese form of FAP. This study showed that there was marked anatomical disruption of the uveoscleral, cornoscleral meshworks and juxtacanalicular tissue characterized by (a) accumulation of amyloid fibrils in the intertrabecular spaces; (b) degeneration of the endothelial cells; (c) homogeneous and/or multilayered plaques of basement membrane-like material loading the intertrabecular spaces or protruding to the lumen of the Schlemm's canal; and (d) degeneration of unmyelinated nerve fibres. These morphological changes and an analysis of the literature suggest that mechanical and neuropathic events can be co-existing factors which enhance the resistance to aqueous humour outflow, leading to increased intraocular pressure and glaucoma in the Portuguese form of FAP.