Transthyretin amyloidosis is an inherited condition that causes a buildup of abnormal proteins in the body called amyloids. They can start to interfere with the function of the patient’s nervous system, causing progressive symptoms. Age at onset can range from 20 to 70, depending on the specific mutations involved, and tends to be earlier in people who come from regions with a long history of the disease, like Portugal and Japan. Treatment options are available and tend to be most effective when provided early.
This condition occurs as a result of an error with the encoding of a protein called transthyretin, which is normally produced in the liver. It normally acts as a transporter for vitamin A and thyroid hormone, and starts carrying amyloid deposits to the nervous system, where they build up over time. There are three forms of the disease: leptomeningeal, peripheral, and cardiac. These forms are named for the different areas of the body they affect.
In patients with leptomeningeal transthyretin amyloidosis, the amyloids build up in the central nervous system, while peripheral patients experience symptoms in the peripheral nervous system like numbness, tingling, and loss of motor control. Cardiac forms attack the heart muscle and cause an irregular heartbeat. Some testing can determine which form a patient has and identify the rogue proteins responsible to learn more about the origins of the condition.
Some medications are available to treat patients with transthyretin amyloidosis. Another option is a liver transplant, especially if it is provided early. The new liver doesn’t carry the defective gene and should code the transthyretin correctly. In patients with existing amyloidosis, it won’t be possible to reverse the effects, but the progression of the disease may stop. Other patients may continue to experience problems, as the amyloids can continue to build up without a carrier protein in some instances.
The gene for this condition is dominant. Someone only needs to inherit one copy in order to express it, and a parent with the disease has a 50% chance of passing it to a child, or a 100% chance if that parent happens to carry two copies of the gene. Parents concerned about transthyretin amyloidosis can meet with a genetic counselor to get more information about their options. This can include some testing to find out more about their genetics, as this could provide helpful insights into how to manage risks of genetic diseases like transthyretin amyloidosis in children.