Familial (or hereditary) amyloidosis, as the name implies, is a heritable form of the disease. Whether a mutation has occurred in one’s own DNA, or was inherited from one’s parents, the most common form of familial amyloidosis is associated with a mutant transthyretin (TTR) protein produced in the liver. TTR is a protein that helps to transport thyroxine
(a thyroid hormone) and retinol (vitamin A) around the body.
There are over 100 known mutations of TTR that cause the protein to become unstable and misfold into amyloid. Various organs are affected, especially the nervous system and heart, with symptoms occurring in mid- to late life. If the nerves are primarily affected, the condition is known as familial amyloid polyneuropathy; if the heart is primarily affected, it is known as familial amyloid cardiomyopathy.