Amyloidosis Types
There are three major types of amyloidosis that are all very different from each other, and each one has a two-letter code. Each code begins with an A, for amyloid. The second letter stands for the protein which makes up the deposits that accumulate.
- Primary Amyloidosis (AL)
Primary amyloidosis is a bone marrow plasma cell disorder and occasionally occurs with multiple myeloma. The deposits in this type of the disease are made up of immunoglobulin light chain proteins, so it is coded AL for amyloid light chain. These light chain proteins are created in the bone marrow by dysfunctioning plasma cells. This is the most common type of amyloidosis in the United States and is usually treated with chemotherapy. Primary amyloidosis is not associated with any other diseases.
- Secondary Amyloidosis (AA)
Secondary amyloidosis is caused by a chronic infection or inflammatory disease such as rheumatoid arthritis, familial Mediterranean fever, osteomyelitis, or granulomatous ileitis. The deposits in this type of the disease are made up of a protein called the AA protein. Medical or surgical treatment of the underlying chronic infection or inflammatory disease can slow down or stop the progression of this type of amyloid. New treatment with a targeted inhibitor molecule is anticipated soon.
- Hereditary Amyloidosis (ATTR)
Familial amyloidoses are rare types of amyloidosis that are inherited and cause disease later in life. The most common form causes amyloid deposits made up of the transthyretin or TTR protein, giving this type the code ATTR. It is found in families of nearly every ethnic background. The transthyretin protein is made in the liver; mutations in the protein cause hereditary amyloidosis. More than 100 different mutations in transthyretin are known and most cause amyloidosis. There are other proteins with mutations which can cause familial amyloidosis also, but these are very rare. They include apolipoprotein A-I, apolipoprotein A-II, gelsolin, fibrinogen, and lysozyme.
- b-2 Microglobulin Amyloidosis
b-2 microglobulin amyloidosis is caused by chronic renal failure and often occurs in patients who are on dialysis for many years. Amyloid deposits are made of the b-2 microglobulin protein that accumulated in tissues, particularly around joints, when it cannot be excreted by the kidney because of renal failure.
- Localized Amyloidosis
There are many types of localized amyloidoses. The most common and best known is Alzheimer’s disease. Localized types of amyloidosis are associated with hormone proteins, aging, or specific areas of the body, and have not been found to develop into systemic amyloidosis. Localized amyloid deposits in the airway (trachea or bronchus), eye, or urinary bladder are made up of light chain proteins, similar to those in AL amyloidosis. However, in localized amyloidosis the abnormal plasma cells producing the amyloid light chains are in the tissues, not in the bone marrow.
|
