Vitreous amyloidosis associated with homozygosity for the transthyretin methionine-30 gene.

Familial amyloidotic polyneuropathy is an autosomal dominant inherited disorder. Biochemical studies have revealed that the amyloid protein in familial amyloidotic polyneuropathy of Japanese, Swedish, and Portuguese origin mainly consists of a variant transthyretin with one amino acid substitution of methionine for valine at position 30, termed TTR met-30. In five Swedish patients with familial amyloidotic polyneuropathy we diagnosed homozygosity for the TTR met-30 gene using restriction fragment length polymorphism analysis. The homozygous individuals did not show more severe systemic symptoms or earlier onset than heterozygotes for the TTR met-30 gene. The only clinical difference was the presence of vitreous opacities in all homozygous patients.