Vitreous involvement in familial amyloidotic neuropathy: a genealogical and genetic study.

Extended genealogical studies stretching back to the 17th century were performed concerning the heredity patterns of vitreous involvement in Swedish patients with familial amyloidotic polyneuropathy (FAP). FAP is an autosomal dominant inherited disorder, characterized by extracellular deposition of amyloid and a clinical syndrome of peripheral and autonomic neuropathy. In addition, some patients show typical vitreous opacities. All patients had their origin in a restricted geographical area. Some main patterns arose from this study: 1) Patients who had vitreous opacities as the first symptom of FAP seem to form a separate group, with a distinct age of onset distribution; 2) The familial occurrence of vitreous opacities raises the possibility that other familial factors modify the expression of the FAP gene; 3) The mean age of onset for vitreous opacities is lower for homozygous than for heterozygous patients.