Amyloid or amyloidosis meaning is a disease characterized by the deposition of an abnormal protein known as amyloid in the connective organs and tissues of the body, which inhibits normal functioning. Amyloid meaning is given as a fibrous and insoluble protein-carbohydrate complex that forms when normally soluble proteins like antibodies become misfolded and adopt a fibril structure. There are various types of amyloid, and every type may be distinguished by the primary protein component that it holds. This is the systemic amyloidosis definition.
Amyloidosis pathology can be systemic (affecting the organs and tissues throughout the body), or it may be localized in tumour-like masses within certain organs. Most of the organs that are commonly affected by the disease (amyloid disease) include the heart, kidneys, spleen (amyloidosis of spleen), liver, skin, and lungs. Symptoms differ based on which organ or organs are affected. For example, symptoms of malnutrition, intestinal bleeding, diarrhoea, and constipation may be associated with the amyloid deposits in the gastrointestinal tract, whereas the symptoms of heart failure and shortness of breath may be associated with the amyloid deposits in the heart.
However, the pathogenesis of amyloidosis, which is also defined as amyloidosis pathology, is quite unclear, because no genetic component has emerged as yet, despite the strong association with the ethnicity of Mexican American.
The below figure shows the duodenum with amyloid deposition (bright pink stain) in the lamina propria.
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Types of Amyloidosis
There are various types of amyloidosis, which may be classified as primary, secondary, or hereditary.
Primary Systemic Amyloidosis
Primary systemic amyloidosis pathology is rare and takes place in the absence of the underlying disease. Typically, the symptoms appear either in the fifth or sixth decade of life and can include skin abnormalities (for example, nodule and discolouration formation), kidney failure, heart failure, and enlargement of the liver and spleen. Though the cause of this particular form is not known, it is associated with the abnormal production of the antibodies present in the bone marrow. These antibodies cannot be broken down, and, resultantly, they enter the bloodstream, and they are eventually deposited in the other tissues in the amyloid proteins form.
In contrast to primary amyloidosis, secondary amyloidosis takes place in association with chronic diseases such as syphilis, tuberculosis, leprosy, rheumatoid arthritis, or Hodgkin disease. Often, secondary amyloidosis affects the liver, kidneys, and spleen. A specific form of amyloidosis characterized by amyloid deposition in the brain is associated with Alzheimer's disease.
Hereditary amyloidosis arises when the genetic mutation, which causes the amyloid protein formation, is inherited. There are various hereditary amyloidosis forms. The most common form is called familial amyloid polyneuropathy (FAP), which is caused by the mutations in a gene designated TTR (transthyretin). Transthyretin protein, which is produced by the TTR gene, generally circulates in the blood and plays an essential role in the transport and tissue delivery of the retinoid and thyroid hormones. Primarily, the FAP affects the nervous system by resulting in abnormal nerve sensation, limb weakness, and pain. In some other cases, amyloid deposits can take place in the kidneys or heart.
Amyloidosis is diagnosed via amyloid protein detection in the urine or blood and through tissue biopsy and imaging studies as well to locate the deposits of amyloid within the organs. Treatment is directed towards symptom reduction. Commonly, agents prescribed for primary amyloidosis include anti-inflammatory drugs, such as colchicine and prednisone, and a few patients can be treated with the chemotherapeutic agent melphalan. In the disease's localized forms, treatment may involve surgical removal of amyloidosis masses. Whereas, in secondary amyloidosis, treatment is aimed at controlling organ damage inflicted by underlying the disease. Patients having advanced amyloidosis may need liver or dialysis, kidney or heart transplantation.
One may not experience the signs and symptoms of amyloidosis until the condition has become advanced. When symptoms and signs are evident, they depend upon the organs that are affected.
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Some Signs and Symptoms of Amyloidosis May Be Given as Follows:
Severe weakness and fatigue
Swelling of legs and ankles
Unable to lie flat in bed because of shortness of breath
Shortness of breath with the minimal exertion
Tingling, numbness, or pain in the feet or hands, especially pain in the wrist (carpal tunnel syndrome)
Unintentional weight loss of above 10 pounds (or 4.5 kilograms)
An enlarged tongue that at times looks rippled around its edge
Diarrhoea, possibly either with blood or constipation
Skin changes, such as easy bruising or thickening, and purplish patches around the eyes
Difficulty in swallowing.
An irregular heartbeat.
There are several various types of amyloidosis. A few of them are hereditary. Others can be caused by outside factors, such as long-term dialysis or inflammatory diseases. Several types affect multiple organs, while the others affect only one part of the body.
Subtypes of amyloidosis are given below.
AL amyloidosis (immunoglobulin light chain amyloidosis)
It is the most common type of amyloidosis in some developed countries. Also, AL amyloidosis is known as primary amyloidosis. Usually, it affects the kidneys, heart, nerves, and liver.