It is defined as material deposited in vivo that is distinguished by the following:
- Fibrillar appearance in the electronic micrograph.
- Eosinophilic amorphous appearance in staining with hematoxylin and eosin.
- Pleated beta sheet structure as observed by the X-ray diffraction pattern.
- The green-apple birefringence in the red histological staining of the Congo (see the second image below).
- Solubility in water and low ionic strength buffers.
All types of amyloidosis consist of a major fibrillar protein that defines the type of amyloid. Polymorphisms that slightly vary native peptides or inflammatory processes set the stage for abnormal protein folding and deposition of amyloid fibrils.
Many classical eponymous diseases were later found related to a diverse range of misfolded polypeptides (amyloids) that contain the common architecture of beta-pleated folds.
The native or wild-type quaternary protein structure is usually born from a single translated protein sequence with an ordered conformation with protein interactions.
However, amyloid fibrils may have different numbers of protofilaments, arrays and conformations of polypeptides.
It is also important to understand that the same polypeptide sequence can produce many patterns with different interactions.
Amyloidosis is a clinical disorder caused by extracellular and / or intracellular deposition of abnormal, insoluble amyloid fibrils that impair normal tissue function.
Only 10% of amyloidosis deposits are constituted by components such as glycosaminoglycans, apolipoprotein-E and amyloid serum P, while almost 90% of the deposits are amyloid fibrils formed by the aggregation of misfolded proteins.
These proteins come, in turn, from other proteins expressed by the cells at the deposition site (localized), or systematically precipitated after production at a local (systemic) site.
In human beings approximately 23 different unrelated proteins are known to form amyloid fibrils in vivo.
Many protein function mechanisms contribute to amyloidogenesis.
Namely, the “non-physiological proteolysis, the physiological proteolysis defective or absent, likewise, the mutations that imply changes in the thermodynamic or kinetic properties and the pathways that are still to be defined.
In this sense, amyloidosis consists of a group of rare but serious conditions, caused by deposits of abnormal protein, called amyloid in tissues and organs throughout the body.
Proteins start as a chain of amino acids that fold into a three-dimensional shape. This “protein folding” allows them to perform useful functions within our cells.
Amyloid, too, is related to a description of proteins that have abnormally bent, which are then collected. In this way they do not break down as easily as normal proteins and can accumulate in tissues and organs.
If this buildup causes the tissues or organs to stop working properly, the resulting conditions are called amyloidosis.
Amyloid deposits occasionally affect only one part of the body (localized amyloidosis), but more often several different parts of the body are affected (systemic amyloidosis), such as the heart, kidneys, liver, or nerves.
Without treatment to treat the underlying cause, amyloid deposits can eventually lead to organ failure and death – sometimes within only a year or two.
There are about 30 different proteins that can malform and form amyloid, so there are many different types of amyloidosis. In general, about 600 new cases of amyloidosis are diagnosed in the UK every year and the majority occur in older people.
Signs and symptoms of amyloidosis.
Amyloidosis can affect any organ, and the symptoms depend on which organs are affected.
Most of the time, amyloid deposits in the kidneys and can cause kidney failure. Symptoms of kidney failure may include fluid retention (edema), tiredness, weakness and loss of appetite.
The amyloid deposited in the heart can cause it to enlarge and impair its ability to pump blood efficiently around the body.
This can cause heart failure, which can cause symptoms such as shortness of breath and edema.
Some of the other possible signs and symptoms of amyloidosis include:
- Sensation of dizziness or fainting, especially after standing or sitting.
- Numbness or tingling sensation in the hands and feet (peripheral neuropathy).
- Foamy urine.
- An irregular heartbeat (arrhythmia).
- Pain in the chest (angina).
- Erectile dysfunction.
- Diarrhea or constipation
- Blood spots on the skin.
- Carpal tunnel syndrome – compression of the nerve in the wrist.
- An enlarged tongue
Amyloidosis usually does not cause problems with memory loss, speed of thought, language, comprehension or judgment.
What causes amyloidosis?
Amyloidosis occurs when an abnormality in the plasma cells found in the bone marrow (the spongy tissue in the center of some bones) results in the excessive production of proteins called “light chains”.
Normally, light chains are part of the antibodies (proteins that help protect the body from disease and infection).
But in cases of amyloidosis, large amounts of misfolded light chains are produced and these are grouped into fibers that the body can not easily erase.
These fibers then gradually begin to form deposits in the heart, kidneys, nerves or liver.
Abnormal white blood cells in the bone marrow are usually benign (non-cancerous), but some cases of amyloidosis are related to a type of bone marrow cancer called multiple myeloma.
Amyloidosis is not inherited, so a person with the disease can not pass it on to their children.
Treatment of amyloidosis.
Currently there are no treatments available that can directly eliminate the amyloid deposits associated with amyloidosis.
The treatment aims to prevent the further production of abnormal light chains while monitoring and treating any problem affecting their organs.
This can give your body enough time to gradually cleanse the deposits before they accumulate again and can help prevent organ damage.
In most cases, this will involve having chemotherapy to damage the abnormal cells of the bone marrow and inhibit the production of abnormal proteins.
You will also need treatment for organ failure, for example, you may need diuretic medications to treat heart failure and you may need dialysis if you have kidney failure.
Some people with kidney failure may be adequate to receive a kidney transplant, although the underlying bone marrow disorder will have to be suppressed by chemotherapy to prevent the buildup of amyloid in the new kidney.
After chemotherapy, you will need regular check-ups every six to 12 months to look for signs if the condition returns (relapsed). If a relapse occurs at any time, chemotherapy may need to start again.