The amyloidoses are a group of diseases in which proteins that are normally soluble deposit extracellularly in tissues as insoluble fibrils. The fibrils have a characteristic beta-pleated sheet configuration that renders them avid for Congo red dye. In the familial amyloidoses, a gene mutation inherited in an autosomal-dominant manner results in a single amino acid substitution that renders a plasma protein amyloidogenic. Mutations in the TTR gene are the most common cause of familial amyloidosis. The clinical features of familial amyloidosis vary depending on the underlying amyloidogenic protein and the particular amino acid affected by the mutation, ranging from peripheral and autonomic neuropathy to cardiomyopathy.
