Amyloidosis is classified into four major types:
• Primary amyloidosis (AL) is the most common form and results from the abnormal production of light chain proteins, which are a part of antibodies. These light chains are produced by blood cells called plasma cells. The light chains can be also increased in multiple myeloma but they do not usually accumulate in tissues as in amyloidosis.
• Secondary (AA) amyloidosis results from the accumulation of serum amyloid protein A as a complication of chronic inflammatory diseases such as Familial Mediterranean Fever (FMF) or rheumatoid arthritis.
• Familial amyloidosis occurs due to genetic mutations in proteins that lead to formation of amyloid fibrils. This type of amyloidosis is inherited. The most common form of familial amyloidosis is caused by a mutation in the transthyretin protein (ATTR).
• Senile amyloidosis, also called “wild type” amyloidosis is caused by an accumulation of normal unmutated transthyretin protein that occurs with aging and especially affects the heart. As the population ages, experts note that TTR cardiac amyloidosis has become more commonplace.
• Localized amyloidosis is an accumulation that occurs in areas such as the larynx or the skin and usually does not need systemic therapy