Prognosis

There are several key factors that affect a patient’s prognosis in familial amyloid polyneuropathy (FAP), but most people with the rare, inherited, progressive disease have a life expectancy of about 10 years after being diagnosed.

FAP is characterized by the accumulation of abnormal protein deposits in nerves and other tissues. In most cases, it is caused by mutations in the TTR gene, which provides instructions for making a transport protein called transthyretin that moves vitamin A and a hormone called thyroxine throughout the body.

Factors affecting prognosis

Life expectancy in FAP depends on factors such as the type of TTR mutation a person has and which organ or organs are affected by the disease. How early a person is diagnosed and treated also plays a role in the disease’s prognosis.

TTR gene mutations

Mutations in the TTR gene typically lead to the formation of a misfolded version of transthyretin, which forms insoluble protein deposits called amyloids in the heart, nervous system, eyes, and other tissues.

Nearly 130 different FAP-related TTR gene mutations have been identified. The most common is the so-called Val30Met mutation, in which the amino acid methionine substitutes the amino acid valine at position 30 of the transthyretin protein sequence. Of note, amino acids are the building blocks of proteins.

Patients carrying this mutation usually start experiencing the first symptoms of FAP in their 30s, which typically include signs of peripheral and autonomic neuropathy, or damage to the nervous system.

Disease progression

Prognosis also is related to disease progression, which can vary among early- and late-onset patients. Early-onset patients, whose symptoms appear between the ages of 30 and 50, usually experience more rapid disease progression. Disease progression is reportedly slower — with a survival rate of up to 20 years — among patients who develop symptoms later on, after the age of 50.

Treatments

Although no medications can reverse the damage caused by amyloid deposits, there are several experimental and approved treatments able to slow the buildup of amyloids in the nervous system and other body parts. These therapies are designed to delay disease progression and improve patients’ life expectancy.

Liver transplant is another way of treating FAP, as the liver is the main source of transthyretin. After a liver transplant, a patient’s prognosis depends on several factors, such as the type of amyloid, diet, age, and how the brain and heart are affected. In general, the earlier a liver transplant is carried out in the overall course of the disease, the better clinical outcomes will be for patients.

 

Last updated: Jan. 7, 2022, by Teresa Carvalho MS

 


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