Transthyretin amyloidosis (ATTR) is a condition in which a protein called amyloid is deposited in your heart, as well as in your nerves and other organs. It may lead to a heart disease called transthyretin amyloid cardiomyopathy (ATTR-CM).
Transthyretin is the specific type of amyloid protein that’s deposited in your heart if you have ATTR-CM. It normally carries vitamin A and thyroid hormone throughout the body.
There are two types of transthyretin amyloidosis: wild type and hereditary.
Wild-type ATTR (also known as senile amyloidosis) isn’t caused by a genetic mutation. The protein deposited is in its non-mutated form.
In hereditary ATTR, the protein is formed incorrectly (misfolded). It then clumps together and is more likely to end up in your body’s tissues.
Your heart’s left ventricle pumps blood through your body. ATTR-CM can affect the walls of this chamber of the heart.
The amyloid deposits make the walls stiff, so they can’t relax or squeeze normally.
This means your heart can’t effectively fill (reduced diastolic function) with blood or pump blood through your body (reduced systolic function). This is called restrictive cardiomyopathy, which is a type of heart failure.
Symptoms of this type of heart failure include:
- shortness of breath (dyspnea), especially when lying down or with exertion
- swelling in your legs (peripheral edema)
- chest pain
- irregular pulse (arrhythmia)
- enlarged liver and spleen (hepatosplenomegaly)
- fluid in your abdomen (ascites)
- poor appetite
- lightheadedness, especially upon standing
- fainting (syncope)
A unique symptom that sometimes occurs is high blood pressure that slowly gets better. This happens because as your heart becomes less efficient, it can’t pump hard enough to make your blood pressure high.
Other symptoms you might have from amyloid deposits in other parts of the body besides your heart include:
- carpal tunnel syndrome
- burning and numbness in your arms and legs (peripheral neuropathy)
- back pain from spinal stenosis
When to see the doctor
If you have chest pain, call 911 immediately.
Seek medical attention right away if you develop these symptoms:
- increasing shortness of breath
- severe leg swelling or rapid weight gain
- rapid or irregular heart rate
- pauses or slow heart rate
There are two types of ATTR, and each has a unique cause.
Hereditary (familial) ATTR
In this type, transthyretin misfolds because of a genetic mutation. It can be passed from parent to child through the genes.
Symptoms usually start in your 50s, but they can begin as early as your 20s.
Protein misfolding is a common occurrence. Your body has mechanisms to remove these proteins before they cause a problem.
As you age, these mechanisms become less efficient, and misfolded proteins can clump and form deposits. That’s what happens in wild-type ATTR.
Wild-type ATTR isn’t a genetic mutation, so it can’t be passed down through the genes.
Symptoms usually start in your 60s or 70s.
Diagnosis can be difficult because the symptoms are the same as other types of heart failure. Tests commonly used for diagnosis include:
- electrocardiogram to determine if the heart walls are thick from the deposits (usually the electrical voltage is lower)
- echocardiogram to look for thick walls and assess heart function and look for abnormal relaxation patterns or signs of increased pressure in the heart
- cardiac MRI to look for amyloid in the heart wall
- heart muscle biopsy to look for amyloid deposits under a microscope
- genetic studies looking for hereditary ATTR
Transthyretin is mainly produced by your liver. For this reason, hereditary ATTR-CM is treated with a liver transplant when possible. Because the heart is often irreversibly damaged when the condition is diagnosed, a heart transplant is usually done at the same time.
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Some of the symptoms of cardiomyopathy can be treated with diuretics to remove excess fluid.
Other medications usually used to treat heart failure, such as beta-blockers and digoxin (Lanoxin), can be harmful in this condition and shouldn’t be routinely used.
Risk factors for hereditary ATTR-CM include:
- a family history of the condition
- male gender
- age over 50
- African descent
Risk factors for wild-type ATTR-CM include:
- age over 65
- male gender
Without a liver and heart transplant, ATTR-CM will get worse over time. On average, people with ATTR-CM live
The condition can have an increasing effect on your quality of life, but treating your symptoms with medication can help significantly.
ATTR-CM is caused by a genetic mutation or is age-related. It leads to symptoms of heart failure.
Diagnosis is difficult because of its similarity to other types of heart failure. It gets progressively worse over time but can be treated with a liver and heart transplant and medication to help control symptoms.
If you experience any of the symptoms of ATTR-CM listed earlier, contact your doctor.