hATTR: It Runs In The Family

The disease known as hATTR amyloidosis is an autosomal dominant disease caused by a mutation in the transthyretin (TTR) gene that results in misfolded TTR proteins accumulating as amyloid fibrils in multiple sites including the nerves, heart, and GI tract.

hATTR amyloidosis affects an estimated 50,000 patients worldwide

hATTR amyloidosis causes
hATTR amyloidosis is a systemic disorder characterized by the extracellular deposition of misfolded transthyretin (TTR) protein. Normally, TTR is a tetramer made up of 4 single-chain monomers. TTR gene mutations are thought to destabilize the protein and cause tetramer dissociation into monomers, which aggregate into amyloid fibrils. These amyloid fibrils then accumulate in multiple organs throughout the body.

In the disease continuum of hATTR amyloidosis, some patients present primarily with polyneuropathy symptoms, historically known as familial amyloidotic polyneuropathy (FAP), and other patients present primarily with cardiomyopathy symptoms, historically known as familial amyloidotic cardiomyopathy (FAC). A substantial proportion of patients present with a mixed phenotype that includes sensory and motor, autonomic, and cardiac symptoms.5,7-9

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The symptom presentation of hATTR amyloidosis is highly varied among patients, even within the same mutation or the same family. In addition to the varied symptom presentation, age of onset varies among patients—with a median age of 39 years, with some presenting as early as their 20s.

As the disease progresses, symptoms of hATTR amyloidosis increase in severity and may eventually rob patients of function—and even their lives.

The Hereditary Nature of hATTR
hATTR amyloidosis is an autosomal dominant disease with variable penetrance. Amyloid deposition or symptomatic disease typically occurs in adults ranging from 30 to 70 years of age, depending on mutation. In fact, more than 120 amyloidogenic TTR mutations have been identified. In the United States, the most common mutations are V122I, T60A, and V30M.

Although some mutations are more predominantly associated with polyneuropathy or cardiomyopathy, many patients with hATTR amyloidosis have mixed clinical phenotypes, including neurologic, cardiac, GI, and other signs and symptoms. Even those mutations on the far end of the spectrum, such as V30M and V122I, often have both cardiac and neuropathic manifestations; however, symptomatology is not always predictable, and it can differ even among affected family members.3

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References: Gertz MA. Hereditary ATTR amyloidosis: burden of illness and diagnostic challenges. Am J Manag Care. 2017;23(suppl 7):S107-S112.