What triggers amyloidosis?

Depending on the cause and pathogenesis features, idiopathic (primary), acquired (secondary), hereditary (genetic), local amyloidosis, amyloidosis in myeloma disease and APUD amyloidosis are distinguished. Secondary amyloidosis is the most common, which is close in origin to non-specific (in particular immune) reactions. It develops with rheumatoid arthritis, ankylosing spondylitis, tuberculosis, chronic osteomyelitis, bronchiectasis, less often with lymphogranulomatosis, tumors of the kidney, lung and other organs, syphilis, nonspecific ulcerative colitis, Crohn's and Whipple's diseases, subacute infective endocarditis, psoriasis, etc. Hereditary amyloidosis in our country is usually associated with a periodic disease that is transmitted by an autosomal dominant type. In this disease, amyloidosis may be the only manifestation. Other forms of hereditary amyloidosis are less common. In particular, Portuguese neuropathic amyloidosis is distinguished, characterized by peripheral polyneuropathy, intestinal dysfunction, sometimes changes in intracardiac conduction, impotence. Amyloid deposits are found in many organs, mainly in the walls of small vessels and nerves. A similar variant of familial amyloidosis has been described in Japan, Switzerland, and Germany. The Finnish variant is amyloidosis with corneal atrophy and cranial neuropathy. Hereditary cardiopathic amyloidosis (Danish type), nephropathic amyloidosis with deafness, fever, and urticaria are also known. Unlike secondary and hereditary amyloidosis, it is not possible to establish the cause or hereditary nature of the disease in primary amyloidosis. In terms of the structure of amyloid and the nature of damage to internal organs, amyloidosis in myeloma disease is close to primary amyloidosis, which is distinguished into a separate group. Recently, attention has been paid to the development of amyloidosis in old age (especially in people over 70-80 years old), when the brain, aorta, heart, and pancreas are affected. New forms of amyloidosis have been described, in particular amyloidosis in patients undergoing chronic hemodialysis, characterized by destructive arthropathy, carpal tunnel syndrome, and bone defects. The nature of the relationship between amyloidosis and atherosclerosis has not yet been clarified, although there are indications that atheromatous changes may promote amyloid deposition.

APUD amyloidosis is a special type of local endocrine amyloidosis, in which the formation of the main component of the amyloid fibril occurs from the products of the vital activity of APUD system cells (apudocytes). This disease often develops with apudomas, tumors from APUD cells. APUD amyloidosis includes amyloidosis of the thyroid gland stroma in medullary cancer, pancreatic islets, amyloidosis of the parathyroid glands in adenoma, pituitary gland, as well as isolated senile amyloidosis of the atria.

Recently, it has been proposed to subdivide amyloidosis according to the biochemical composition of amyloid fibrils.

• AA-amyloid is the most common amyloid protein, the serum analogue of which is the SAA protein. This type of amyloid protein is found in secondary amyloidosis and amyloidosis in periodic disease. Its serum precursor (SAA) is a protein that is present in the blood serum in acute inflammation, tumors, pregnancy, rheumatic diseases and other conditions. SAA protein has been shown to be synthesized by hepatocytes, and its synthesis is initiated by interleukin 1.
• AF amyloid is found in hereditary forms of amyloid polyneuropathy. It is likely that the serum precursor of AF is one of the polymorphic forms of normal prealbumin. AL amyloid consists of Ig and fragments of Ig light chains.
• In the 1980s, carpal tunnel syndrome, caused by amyloid deposition in the synovial membrane (AN-amyloid), began to be frequently detected in patients undergoing long-term hemodialysis. β ₂ -Microglobulin is the serum precursor of this type of amyloid protein.
• AS amyloid is observed in a clinically heterogeneous group of elderly patients. The serum precursor of this type of amyloid protein is prealbumin.