source: National Organization for Rare Disorders summary/abstract:
Amyloidosis is a systemic disorder that is classified into several types. The different types of amyloidosis are classified as systemic or localized. AL (immunoglobulin light chain, historically known as primary) amyloidosis is the most common type of systemic amyloidosis. AL amyloidosis results from an abnormality (dyscrasia) of a type of white blood cell called plasma cells in the bone marrow, and is closely related to multiple myeloma. AA (historically known as secondary) amyloidosis is derived from the inflammatory protein serum amyloid A.
AA amyloidosis occurs in association with chronic inflammatory disease such as the rheumatic diseases, familial mediterranean fever, chronic inflammatory bowel disease, tuberculosis or empyema. Hereditary amyloidosis is a rare type of amyloidosis that is caused by an abnormal gene.
There are several abnormal genes that can cause hereditary amyloidosis, but the most common type of hereditary amyloidosis is called ATTR and caused by mutations in the transthyretin (TTR) gene. Age related amyloidosis, in which the amyloid is derived from wild-type (normal) transthyretin, is a slowly progressive disease that affects the hearts of elderly men and is called ATTRwt amyloidosis.