What causes hereditary ATTR (hATTR) amyloidosis?

hATTR amyloidosis is caused by a gene change (mutation) that affects the function of a protein in the blood called transthyretin (TTR). This protein is made primarily in the liver.

How hATTR amyloidosis develops

A gene mutation (change within a gene) causes the TTR protein to take on an abnormal shape and build up in the nerves, heart, GI tract, and other organ systems

TTR, a naturally occurring protein made primarily in the liver, helps carry substances such as vitamin A.
Gene mutations can lead to changes in the TTR protein that cause it to misfold (take on an abnormal shape).
The change in shape causes the protein to gather and build up in the nervous (nerve), cardiac (heart) and gastrointestinal (digestive) systems. These gathered proteins are called amyloid fibrils. The amyloid fibrils build up and form deposits, which is what causes symptoms.

hATTR amyloidosis can cause a range of symptoms

The symptoms of hATTR amyloidosis can vary widely among people with the same mutation and even within families, though some do see a pattern of symptoms develop. Different symptoms may appear at different times for each individual. The age at which initial symptoms appear may vary, ranging from the mid-20s to the mid-60s.

hATTR amyloidosis affects several parts of the body, including:

The peripheral nervous system, which is made up of nerves that branch out from the brain and spinal cord and communicate with the rest of the body, including your arms and legs

Polyneuropathy is caused by damage to the nerves of the peripheral nervous system, resulting in improper function

The cardiac system, which includes the heart and blood vessels, transports blood through veins and delivers oxygen to cells in the body

Cardiomyopathy is a disease of the heart muscle that leads to heart failure

The autonomic nervous system, which is made up of nerves that connect the brain and spinal cord to organs such as the heart, stomach, and intestines, and helps to control bodily functions such as breathing, digestion and heart rate

Autonomic dysfunction occurs when the autonomic nervous system is not working correctly and may affect involuntary bodily functions

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