Amyloidosis of the kidneys
A century before the discovery of prion diseases, Virchow gave a new name for fat disease. This long known disease is characterized by the fact that the organs are enlarged, pale, compacted and cease to function. They look as bacon and from this fact comes the name of the disease. Virchow found the following: if the cut surface of an organ with amyloidosis is inundated with Lugol solution and dilute sulfuric acid, it is stained in bluish purple color. The cut surface of potato, if inundated with iodine (Lugol solution) is stained in the same color. What a potato consist of? Strach. It is its main ingredient, and also of many vegetables. Potatoes are rich in this storage form of carbohydrates. How to be called a disease in which the organs resemble the accumulation of starch? The suffix “oid” means “similar”. The scientific name of the starch is amilon. Hence the name of the disease – Amyloidosis.
Amyloidosis is a disease in which in tissues is delayed an abnormal protein called amyloid. This is a protein that normally does not exist in the body and it is produced in some diseases. This protein is deposited in different organs depending on forms of amyloidosis. Amyloid is almost insoluble in chemicals and intractable to the action of enzymes, hormones and antibodies in the body. Something more- this is a foreign protein, although synthesised in the body, but the immune system does not react against amyloid.
Once deposited in tissues, the abnormal protein remains probably till the end of life. The problem is that once deposited in tissues, it damages the metabolism and thus impairs parenchymal cells of organs. They could not fully perform their functions and eventually die. Amyloid is deposited in interstitium– intercellular substance. It damages the blood flow in tissues and interrupt the flow of water, electrolytes, mineral substances and waste products to and from parenchymal cells.
Amyloidosis of the kidney very rare may occur as a single disease. In most cases it is an organ form of systemic amyloidosis, which involve almost all vital organs. Generalized forms of amyloidosis are two – primary and secondary.
Amyloidosis of the kidney in primary generalized amyloidosis is developing in patients who suffer from a rare type of cancer called multiple myeloma. This tumor originates from plasma cells. These are cells that produce antibodies in healthy organism. Because of their tumor degeneration, instead of normal, they begin to produce abnormal, ugly antibodies. Protein molecules of antibodies are defective, not fully completed and functionally unsuitable. These incomplete antibodies circulate in the blood in large quantities because myeloma (cancer) cells produce them continuously. Circulating in the blood, these immunoglobulin molecules pass through all tissues of the body. Here they are captured and decomposited by one type tissue white blood cells called macrophages. In 85-90% of patients with myeloma things finish here. In the other 10-15% of patients, tissue macrophages instead of capturing and disposing defective antibody molecules, for unknown reasons begin to use them as building material, to connect them with each other and to form the pathological protein amyloid.
After they have it built up in their cytoplasm, they export them into the intercellular space and they are deposited in there. The more amyloid is deposited in the space between cells, the more difficult is the metabolism between them and capillaries. Cells are literally starving and die poisoned by their own toxins and lack of oxygen.
Amyloidosis of the kidney in secondary generalized form is developed by the same mechanism. The causes may be numerous chronic inflammatory diseases. In the past, with amyloidosis of the kidney were complicated tuberculosis, osteomyelitis, bronchiectasis disease, lung and liver abscesses. With the development of surgery and the advent of antibiotics in medical practice, the importance of these diseases is decreased. Systemic diseases of connective tissue and autoimmune diseases today are the main reasons for the development of renal amyloidosis.
In local forms of amyloidosis amyloid is deposited only in certain organs, without other accompanying diseases in these patients. Many other forms of amyloidosis are known – hereditary familial amyloidosis, familial Mediterranean fever, familial amyloid polyneuropathy, senile amyloidosis.
Amyloidosis of the kidneys leads to characteristic changes in them, which can be suspected in ultrasonographic examination. The kidneys are enlarged, solid and diffuse pale. This is the initial stage in which they are called large white kidney. Accurate diagnosis of the disease is made by renal biopsy. The kidney is punctured under ultrasound guidance with a thick needle. In this operation is taken a piece of kidney tissue with dimensions smaller than a quarter of a match.
Microscopic examination of amyloid shows pink structureless proteinaceous material in the renal glomeruli. For confirmation of the diagnosis and exclusion of other depositions are carried out additional stains to demonstrate amyloid, most important of which is the staining with Congo red called “Congo Roth”. Only amyloid is stained in orange red. All other depositions of proteins are negative. Stained with Congo Roth amyloid in polarized light glows bright green.
Amyloidosis of the kidneys leads cease of their functions with the development of renal failure. Patients usually come to hemodialysis. For treatment are tried different products with the aim to degradate and remove amyloid deposits, but they are very stable and difficult prone to resorption. Much important is prevention of the development of amyloidosis of kidney disease as a complication of the causing diseases. This is achieved by correct and complete cure of this diseases. In some cases it is performed periodically plasmapheresis. This operation aims purifying of the blood of proteins that serve as starting material in the construction of amyloid. Usually in amyloidosis of kidneys the prognosis is poor.