AL Amyloidosis is a plasma cell disorder characterized by the aggregation and deposition of insoluble amyloid fibrils derived from misfolding of monoclonal immunoglobulin light chains usually produced by a plasma cell tumor (see this term). It usually presents as primary systemic amyloidosis (PSA) with multiple organ involvement and less frequently as primary localized amyloidosis (PLA; see these terms) restricted to a single organ.