Diseases affecting the heart: cardiac amyloidosis

By Cristiano Antonino Last updated Jun 9, 2023

The term amyloidosis refers to a group of rare, serious conditions caused by deposits of abnormal proteins, called amyloids, in tissues and organs throughout the body

Proteins originate from amino acids that fold into a three-dimensional shape; normally, this allows them to perform their functions in cells.

This folding produces amyloid, a substance that, unlike proteins, is not easily broken down, a substance that when deposited causes organs and tissues to malfunction.

This results in amyloidosis

Amyloid deposits will mostly affect organs, such as the heart, kidneys and liver, in which case it will be called systemic amyloidosis; it is rarer that they may affect one part of the body, in which case it will be called localised amyloidosis.

Untreated amyloid accumulation leads to poor or total functioning of the affected organ; an organ that, depending on its importance to the body’s vital functions, may even lead to death.

There are around 30 proteins that can lead to amyloid formation; in Italy, cases of amyloidosis number around 800 per year.

SYMPTOMS OF AMYLOIDOSIS

Any organ can be affected by amyloidosis; the symptoms that occur will depend on the organ affected by the accumulation of abnormal proteins.

When there is accumulation in the kidneys, kidney failure will occur. Other symptoms will be fatigue, weakness and lack of appetite.

If there is amyloid accumulation in the heart, it may lead to an increase in the size of the heart, impairing its function of pumping blood flow to the rest of the body.

The amyloid will progressively damage the functioning of the heart cells.

The walls will stiffen and have a slowed release, diastolic dysfunction will occur, and the force of contraction will also be reduced, systolic dysfunction will occur.

Symptoms, such as palpitations and dyspnoea, will progressively manifest themselves, with the appearance of atrial and ventricular arrhythmias up to congestive heart failure.

Other likely symptoms may include: feeling faint associated with dizziness; numbness or tingling sensation in the extremities of the lower and upper limbs; foamy urine; irregular heartbeat; chest pain; diarrhoea or constipation; blood spots on the skin; carpal tunnel syndrome.

Amyloidosis may also cause problems with memory, formulation and speed of thought, language, and comprehension.

Primary amyloidosis will occur when there is an abnormality in the plasma cells in the bone marrow that leads to an excessive production of light-chain proteins, which is why it is called light-chain amyloidosis.

Usually the light chains form part of antibodies, which in the case of amyloidosis will be produced in large quantities, will eventually aggregate into linear, rigid fibres that the body is unable to eliminate and deposits will therefore form in the heart, kidneys, nerves or liver.

Light-chain amyloidoses are not hereditary.

Less common amyloidoses include:

chronic inflammatory reactive amyloidosis, which will occur as a result of a long-term inflammatory disease, such as rheumatoid arthritis. Treating the disease that caused it often prevents the amyloidosis from worsening and can thus bring improvements;
hereditary amyloidosis, resulting from heredity. If the liver is affected, and its function is impaired, transplantation may be necessary;
ATTR amyloidosis, caused by amyloid deposits consisting of a protein called transthyretin (TTR). It can be both hereditary and non-hereditary.

Transthyretin amyloidosis may require a liver or heart transplant in some cases.

The diagnosis of light-chain amyloidosis can be complicated as the symptoms it causes are generic; amyloidosis can be confirmed by performing a biopsy of the affected body part to check for the presence of amyloid proteins.

Tissue sampling varies depending on the air affected in order to ascertain whether amyloidosis is present.

In some cases it will be performed by taking small amounts of fat from the belly using a needle; in the case of a biopsy of the intestine, tissue will be taken during endoscopy.

In order to diagnose amyloidosis, the following may be performed

electrocardiogram in order to check the health of the heart;
SAP scintigraphy which, by injecting a radioactive version of the amyloid protein, will make it possible to identify and localise amyloid deposits in the body.

There are currently no therapies aimed at removing the deposits associated with light-chain amyloidosis.

However, therapies are aimed at preventing their further production and keeping under control the problems that may be triggered in the affected organs; this will allow the body to have a window of opportunity to eliminate the deposits before new ones can form.

In the vast majority of cases, chemotherapy will be necessary in order to eliminate abnormal bone marrow cells by preventing them from producing abnormal proteins.

Those who will suffer kidney failure due to amyloid accumulation in the kidneys may have to resort to transplantation; and to prevent amyloid accumulation in the new organ as well, chemotherapy will be necessary.

It will be necessary, following chemotherapy, to have check-ups every six months or so to avoid relapses.

Relapses that, should they recur, will require chemotherapy again.