Amyloidosis: What Every Physician Needs to Know

Amyloidosis is a term for diseases caused by extracellular deposition of protein fibrils. The accepted nomenclature is "AX", "A" for amyloidosis, and "X" indicating the precursor protein. If the precursor is an immunoglobulin light chain, the disease is termed AL, the most common of the systemic amyloidoses. If it is familial (AF), the precursor protein can be an inherited mutant serum protein such as transthyretin, abbreviated ATTR, or proteins such as lysozyme, fibrinogen, gelsolin, or apolipoproteins.

The old nomenclature of "primary" and "secondary" is no longer used, although AA amyloidosis, involving formation of fibrils from serum amyloid A (SAA) protein, is truly secondary to chronic inflammatory or infectious states, as SAA is an acute phase reactant.