Common Types of Cardiac Amyloidosis

There are over 30 proteins that can cause amyloidosis. However, two of them commonly affect the heart causing cardiac amyloidosis.

This is a bone marrow disease. Bone marrow has red blood cells and many types of white blood cells. White blood cells produce antibodies which are proteins that fight against infections. Light chains are pieces of antibodies produced by one kind of white blood cell called plasma cells. In light chain amyloidosis, plasma cells produce too many abnormal light chains that do not function normally. 

These light chains stick together, forming long strings called "amyloid." These amyloids then accumulate in different organs leading to organ failure. Any organ can be affected. However, commonly affected organs are kidneys, heart, nerves (neuropathy and bilateral carpel tunnel), stomach and intestines. ; 

The liver produces the protein called transthyretin. This protein carries vitamin A and thyroid hormone in our body. However, this protein can become unstable and break apart due to either genetic mutation or aging, losing its function. This abnormal protein then sticks together, forming long threads called "ATTR amyloid." 

ATTR is now known to be the most prevalent form of cardiac amyloidosis. Previously, ATTR was thought to be a rare disease with no specific treatment. The diagnosis was made only from a biopsy. However, with recent advances in this field, we now have a test to diagnose it without an invasive biopsy and have specific treatment. ATTR amyloidosis is not uncommon but is an underdiagnosed disease.  

There are two sub-types of transthyretin (ATTR) amyloidosis:

This form of ATTR amyloidosis is caused by a genetic mutation. This can be passed on from one generation to another. Patients with hereditary ATTR are younger when they start experiencing symptoms. This type of amyloidosis can affect nerves, heart, or both. There are 120 genetic mutations known to cause ATTR. Some mutations are more common in certain ethnic or racial groups, like the T60A mutation in people with Irish ancestry or the V122I mutation in African ancestry. Hereditary ATTR is an autosomal dominant disease, meaning only one affected parent is required to pass on the mutation to the offspring. Hereditary ATTR can also occur from new mutation without any prior family history.  

This type of ATTR affects older individuals and was previously called senile amyloidosis. Transthyretin protein breaks up and forms transthyretin amyloid. This commonly affects the heart causing congestive heart failure. It can also cause carpel tunnel (often in both hands), lower back pain (due to spinal stenosis), multiple joint pain, spontaneous biceps tendon rupture, atrial fibrillation, heart blocks and aortic stenosis. 

International experts recommend screening patients older than 65 years with increased heart wall thickness and congestive heart failure symptoms (shortness of breath, lower leg swelling, abdominal swelling) for wild-type ATTR amyloidosis. Early diagnosis and treatment initiation has proven to improve the quality of life in patients with this condition.