Homozygosity for the transthyretin-Met30 gene in three Japanese siblings with type I familial amyloidotic polyneuropathy.

Abstract

We report the cases of three siblings homozygous for a mutated transthyretin (TTR) gene that causes type I familial amyloidotic polyneuropathy (FAP), in whom we made the diagnosis by identifying both the mutated TTR gene and a variant TTR in their sera. Their serum levels for the variant TTR are twice those of patients heterozygous for the gene, but two have late-onset FAP and the third is an elderly asymptomatic carrier. TTR abnormality is a necessary condition for the development of FAP, but there may be other factors that retard or prevent its clinical development.