Major systemic types include AL (primary amyloidosis): Caused by acquired overexpression of clonal immunoglobulin light chains AF (familial amyloidosis): Caused by inheritance of a mutant gene encoding a protein prone to misfolding, most commonly transthyretin (TTR) ATTRwt (wild-type ATTR; previously termed senile systemic amyloidosis or SSA): Caused by misfolding and aggregation of wild-type TTR AA (secondary amyloidosis): Caused by aggregation of an acute phase reactant, serum amyloid A Amyloidosis caused by aggregation of beta-2-microglobulin can occur in patients on long-term hemodialysis, but the incidence has declined with use of modern high-flow dialysis membranes.