Familial transthyretin amyloidosis (FTA) is a rare inherited condition characterized by abnormal build-up of a protein called amyloid in the body's organs and tissues. Signs and symptoms depend on where the amyloid protein is building up. Amyloid build-up in the nerves of the peripheral nervous system causes a loss of sensation in the lower limbs, feet, and hands (peripheral neuropathy). Amyloid build-up can also affect the involuntary body functions, such as blood pressure, heart rate, and digestion. Other areas of the body that may be affected are the heart, kidneys, eyes, and gastrointestinal tract. FTA is caused by changes in the TTR gene. Inheritance is autosomal dominant, but not all people with a TTR genetic change will develop FTA. Diagnosis of FTA is suspected by signs and symptoms and confirmed by tissue biopsy and genetic testing.