Cardiac amyloidosis is a life-threatening disease. There are two major types and fortunately we have effective therapies for both, provided they are diagnosed early. One type is caused by a piece of an antibody called a “light chain” (because it is a small protein) and the other is caused by a protein made in the liver that carries vitamin A, called transthyretin. These two types, AL (for amyloid light chain) and ATTR (for amyloid transthyretin), are different and require different diagnostic and therapeutic approaches.
For patients with AL, the treatment is aimed at eliminating the abnormal cells in the bone marrow that produce the AL light chains. For those with ATTR, the treatment aims to reduce production of transthyretin by the liver or to stabilize the transthyretin molecule. ATTR can be due to changes in the normal transthyretin molecule (ATTRwt) or by mutated transthyretin (ATTRv), a hereditary form of the disease. Both AL and ATTR are treatable and the treatments enable patients to resume their lives and live longer.
In rare cases, heart biopsies are required to type the amyloid that a patient may have. We are fortunate to have expert cardiology teams here at Tufts MC to help when biopsies are needed. Heart biopsies are considered to be quite safe when performed in experienced centers. Figure 1 shows the slides from a heart biopsy, the one on the left stained with the standard amyloid stain called Congo red and the one on the right showing the fibrils of amyloid seen with the highly powerful magnification technique of electron microscopy.
Although AL and ATTR are both types of amyloidosis, there may be subtle differences in the symptoms that patients have. AL often involves the kidneys, for example, and can cause swelling of the legs due to protein losses in the urine. ATTR almost never does. Some of these different presentations are shown in Figure 2.
At Tufts MC, we are also fortunate to have expert cardiologists and nuclear cardiology specialists who can employ and interpret the newest scans for cardiac amyloidosis that may make heart biopsy unnecessary. For more information on our leading cardiac amyloid specialist, Dr. Ayan Patel, please visit the Cardiac Amyloidosis Program.