What causes it?

hATTR amyloidosis is passed down through family members and is an autosomal dominant condition, meaning a person only needs to inherit one copy of the affected gene from one parent to develop the condition. If one parent has hATTR amyloidosis, there is a 50 per cent chance their child will inherit the mutation.

Inheriting a mutated copy of the TTR gene does not always lead to disease or symptoms. However, even without symptoms, a parent with an altered copy of the gene is a carrier and still has a 50 per cent chance of passing on the mutation.

Although hATTR amyloidosis is a hereditary condition, some families may be unaware of a history of the condition in their family.

What are the signs and symptoms?

hATTR amyloidosis can manifest itself in many ways and with a broad range of symptoms, depending on where the amyloid protein is building up in the body. Most frequently, the protein deposits occur in the peripheral nervous system, causing polyneuropathy, which can result in a loss of sensation, pain, or immobility in the arms, legs, hands, and feet.

Fact Sheet – Hereditary Amyloidosis Facts

Common symptoms include:

• • Cardiomyopathy
    Shortness of breath, palpitations and abnormal heart rhythm, ankle swelling (edema), fainting, fatigue, chest pain (angina)
  • Peripheral neuropathy
    Tingling and numbness in legs and feet, difficulty walking, limb weakness and pain
  • Autonomic neuropathy
    Light-headedness when standing (orthostatic hypotension), bladder problems, bowel problems, sexual dysfunction
  • Gastrointestinal
    Decreased appetite, diarrhea, nausea, stomach pain, weight loss

How is hATTR diagnosed?

Misdiagnosis is common with hATTR amyloidosis because the symptoms can resemble those of other conditions. This often results in patients having to see five or more physicians across multiple specialties before receiving an accurate diagnosis of hATTR amyloidosis.

As a first step, it is important for a physician to conduct a thorough physical exam and get a detailed patient medical history to help determine which form of the disease a person has. The physician may also conduct the following tests and procedures:

• Blood, urine, nerve, and muscle tests; echocardiogram; MRI
  To determine the effect of the amyloid deposits on the heart, nerves, and other organs.
• Scintigraphy (bone scans)
  To non-invasively diagnose hATTR amyloidosis with cardiomyopathy.
• Biopsy
  To determine the presence of TTR amyloid protein. The tissue sample for the biopsy may be taken from a person’s belly fat, bone marrow, or sometimes the mouth, rectum, or other organs.
• Immunohistochemistry (a lab test that uses antibodies attached to an enzyme or fluorescent dye to test for certain antigens within a tissue sample) and mass spectrometry (a test that measures the masses within a tissue sample)
  To differentiate between ATTR (wild-type and hereditary) and AL amyloidosis.
• Genetic testing
  If the patient is diagnosed with hATTR amyloidosis, the physician may recommend that other members of their family consider undergoing genetic testing.

People living with hATTR amyloidosis require an early and accurate diagnosis due to the rapid, natural progression of the disease. It’s important to talk to your healthcare provider to learn about treatment options for hATTR amyloidosis.

How is hATTR managed and treated?

Existing Treatment Options

Liver Transplant
Until recently, a liver transplant was the only option for treatment of hATTR amyloidosis. TTR is made mostly by the liver, and a transplant will reduce the production of the abnormal TTR protein. The outcome of liver transplantation is largely dependent on the mutation that exists in the patient.

Diflunisal
Approved as a non-steroidal, anti-inflammatory drug (NSAID) and is shown to bind to the TTR protein in the blood, thereby preventing the formation of amyloid. Studies are currently underway to assess the effect of diflunisal on the progression of neuropathy and cardiomyopathy in patients with hATTR amyloidosis.

Novel Treatment Options

Three Health Canada approved therapies have been developed: Tegsedi™ (inotersen), Onpattro™ (patisiran) and Vyndaqel™ (tafamidis). These therapies treat the underlying cause of hATTR amyloidosis. These, and other drugs that are currently under development, take different therapeutic approaches to treating hATTR and are aimed at:

Stopping the production of TTR proteins
The approach of stopping the production of TTR proteins is to prevent TTR protein production by blocking or ‘silencing’ the TTR gene.

• Inotersen (Tegsedi™) – Approved following priority review by Health Canada in October 2018 for the treatment of stage 1 or stage 2 polyneuropathy in adult patients with hATTR amyloidosis. Inotersen was also approved in Europe in July 2018 and in the US in October 2018.
• Patisiran (Onpattro™) – Approved following priority review by Health Canada in June 2019 for the treatment of polyneuropathy in adult patients with hereditary transthyretin-mediated (hATTR) amyloidosis. Patisiran was also approved in the US and Europe in August 2018 for the treatment of hATTR amyloidosis in adults with stage 1 or stage 2 polyneuropathy.

Stabilizing the TTR protein
The approach of TTR stabilizers is to stop the TTR protein from forming amyloid deposits.

• Tafamidis (Vyndaqel™) Approved following priority review by Health Canada in January 2020 for the treatment of transthyretin amyloid cardiomyopathy in adult patients. Tafamidis was approved in the US in May 2019 and in Europe in February 2020.

Supportive Care

Supportive care options are aimed at managing symptoms. Due to the progressive nature of hATTR amyloidosis, managing symptoms is an ongoing process. Examples that a physician may recommend include:

• Diuretic medicine to remove extra water from the body
• Thickeners to add to fluids to prevent choking if a person has trouble swallowing
• Compression stockings to relieve swelling in the legs or feet
• Dietary changes, especially for people who have gastrointestinal amyloidosis