Key Information
Familial amyloidosis (synonym for familiar amyloid polyneuropathy [FAP]) is an autosomal dominant inherited disease, caused by mutations in the transthyretin (TTR) gene, coding for the corresponding protein consisting of 127 amino acids. It was first described by the Portuguese neurologist Andrade. The TTR gene is located on chromosome 18q. More than 100 different mutations are known. The most common mutation is the Val30Met mutation, endemically found in Portugal, Sweden, and Japan. Among the other mutant proteins that are of etiological importance but are very rare, is apolipoprotein I and II, or fibrinogen A.
Transthyretin is a tetramer, built out of four identical TTR-subunits. Point mutations of the gene lead to a destabilization of the protein and subsequently to protein misfolding, resulting in the extracellular deposition of mutated amyloid in several tissues, predominantly in peripheral/autonomic nerves, gastrointestinal tract and myocardium.