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Wild-type amyloidosis is a disease in which the body makes abnormal proteins that build up in the heart and other tissues. This condition mostly affects men who are at least 60 years old. Experts estimate that at least 1 percent of men over the age of 80 have wild-type amyloidosis. However, because heart problems are common in older men and are often caused by other conditions, some researchers think that wild-type amyloidosis often goes undiagnosed. The actual prevalence of this condition may be higher.
Wild-type amyloidosis may also be called wild-type ATTR amyloidosis, ATTRwt amyloidosis, or wild-type transthyretin (TTR) amyloidosis. Previously, doctors called this disease senile systemic amyloidosis or senile cardiac amyloidosis. Despite what these former names may suggest, wild-type amyloidosis is not known to be directly related to dementia. It is, however, related to aging.
Normally, cells make proteins that perform specific tasks. In people with amyloidosis, cells produce high levels of abnormal proteins. These proteins don’t fold into the correct shape. They stick together, forming clumps called amyloid deposits or amyloid fibrils. The amyloid deposits build up within different parts of the body.
There are several types of amyloidosis. Each type is caused by a different misfolded protein and tends to affect different tissues in the body. Wild-type amyloidosis is caused by a type of protein called transthyretin. When the liver makes too much of this TTR, amyloid deposits often form in the heart.
Wild-type amyloidosis is related to another type of amyloidosis called hereditary or familial ATTR amyloidosis. Hereditary ATTR amyloidosis is caused by a gene mutation that is passed down through families. The gene mutation causes the liver to make abnormal, mutated TTR proteins that build up in the nerves, kidney, and heart.
Unlike hereditary ATTR amyloidosis, wild-type ATTR amyloidosis is not caused by gene mutations and doesn’t run in families. People with wild-type amyloidosis make high levels of normal TTR protein. The term “wild type” means that the protein is not mutated (not changed). Doctors don’t know why the normal TTR protein forms amyloid fibrils in people with wild-type amyloidosis.
Wild-type amyloidosis often leads to cardiomyopathy — heart muscle disease. Amyloid deposits in the heart make the muscle become thick and stiff, making it harder for the heart to beat properly. Signs and symptoms of wild-type amyloidosis are similar to those of congestive heart failure. They may include:
Amyloid deposits can also form in the nerves, leading to additional symptoms. Many people with wild-type amyloidosis have carpal tunnel syndrome. This condition causes numbness, weakness, tingling, or pain in the hand or wrist. Occasionally, wild-type amyloidosis also causes peripheral neuropathy, which can lead to pain or numbness in various parts of the body.
Wild-type amyloidosis may also lead to a tear in the biceps tendon (the tendon that attaches the muscle in the upper arm to bones in the elbow and in the shoulder). A tear can cause the muscle to bulge out or lead to pain in the elbow or shoulder. Non-heart-related symptoms may appear up to 10 years before heart symptoms.
Heart problems are common in older men, and wild-type amyloidosis may look similar to other cardiac conditions. However, getting a correct diagnosis is important because some of the medications that help treat other forms of heart disease can be harmful to people with wild-type amyloidosis.
Tests that may be used to diagnose wild-type amyloidosis include:
During an exam, a doctor will ask about symptoms and look for signs of amyloidosis or other conditions.
Doctors measure how well the heart is working using tests such as an echocardiogram or an electrocardiogram (EKG). These tests capture images of the heart and identify damage.
Imaging tests, such as cardiac magnetic resonance imaging or ultrasound, can help show organ damage.
Doctors may also use a nuclear imaging test. This test uses a small amount of radioactive material to show whether a person has amyloid deposits. Sometimes, a nuclear imaging test combined with a blood test is enough to diagnose wild-type amyloidosis. In other cases, a biopsy is needed.
If a doctor suspects amyloidosis, they may recommend a biopsy. During a biopsy, doctors remove a small sample of tissue. Amyloidosis diagnosis may include taking a biopsy of the abdominal fat. If a person has cardiac symptoms, they may also need a biopsy of the heart tissue. Moreover, if evidence of light chains — pieces of antibodies made by white blood cells in the bone marrow — are found in blood testing, then a biopsy is still needed to establish the diagnosis and type of amyloidosis.
After a biopsy sample is removed, it is sent to a laboratory for further studies. The tissue can be stained with Congo red, a dye that makes amyloid proteins glow. This test helps doctors determine whether amyloid deposits are building up in the body.
Doctors may need to run other tests to determine the type of amyloidosis. Hereditary ATTR amyloidosis and amyloid light-chain amyloidosis also affect the heart, so these other conditions need to be ruled out. Some hospitals may use immunohistochemistry, mass spectrometry, or genetic tests to determine what type of amyloidosis is present.
A lab may run a protein sequence analysis test on a biopsy sample to see which type of protein is affected. If this test shows that the TTR protein is involved, then a simple blood sample is sent to a lab for a genetic-sequencing test to examine the DNA chains. If this test produces no identifiable mutations, then wild-type ATTR is the resulting diagnosis.
Doctors may also perform other laboratory tests, including blood or urine tests, to determine whether the organs are working correctly. Additionally, certain blood tests may be used to track amyloidosis over time. These tests look for biomarkers — molecules that serve as signs of how advanced the disease is and how much amyloidosis-related heart damage has occurred.
Wild-type amyloidosis generally affects the heart, so most people with this condition will be treated by a cardiologist — a doctor who specializes in heart diseases. Treatments may have two different goals. Some therapies help slow down the disease and keep the amyloidosis under control. Other treatments help relieve symptoms of amyloidosis and improve quality of life.
The U.S. Food and Drug Administration (FDA) has approved two drugs to treat heart disease in people with wild-type amyloidosis: Vyndaqel (tafamidis meglumine) and Vyndamax (tafamidis). They work by stopping the TTR protein from forming amyloid fibrils.
Another medication, Dolobid (diflunisal), works in a similar way. Diflunisal is not officially approved to treat amyloidosis, but doctors may choose to use it off-label. Tafamidis, tafamidis meglumine, and diflunisal may improve survival rates, helping people with wild-type amyloidosis live longer.
Researchers have developed other drugs that act as gene silencers, blocking the TTR gene and preventing the body from making TTR protein. A couple of these drugs have been approved to treat hereditary ATTR amyloidosis. Researchers are now conducting clinical trials to study whether these drugs can also help people with wild-type amyloidosis.
People with wild-type amyloidosis may take some of the same medications that are prescribed to people with congestive heart failure. Doctors may prescribe diuretics to get rid of extra fluid in the body, or blood thinners to help prevent blood clots. Eating a diet that is low in sodium (salt) also helps remove extra fluid and may reduce symptoms.
Medications such as beta blockers, calcium channel blockers, and ACE inhibitors are sometimes used to treat heart problems. However, people with wild-type amyloidosis should not take these medications because they can cause additional damage.
Some people with severe wild-type amyloidosis experience a lot of heart damage. In this case, doctors may recommend a heart transplant. During this surgery, a person’s heart is replaced with a heart from a donor.
People live for an average of 3.9 years after being diagnosed with wild-type amyloidosis. A little more than 1 out of 3 people with this condition live for five years or more after diagnosis.
Wild-type amyloidosis is a disease that develops relatively slowly. Although amyloid deposits continue to build up within organs over time, this is a slow process. As a result, people with wild-type amyloidosis often have a better prognosis than those with other types of amyloidosis.
MyAmyloidosisTeam is the social network for people with amyloidosis and their loved ones. On MyAmyloidosisTeam, members come together to ask questions, give advice, and share their stories with others who understand life with amyloidosis.
Are you living with wild-type amyloidosis? Share your experiences in the comments below, or start a conversation by posting on MyAmyloidosisTeam.
Mark Levin, M.D. is a hematology and oncology specialist with over 37 years of experience in internal medicine. Review provided by VeriMed Healthcare Network. Learn more about him here.
Maureen McNulty studied molecular genetics and English at Ohio State University. Learn more about her here.
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