Monarch Disease Ontology id MONDO_0017816 (primary systemic amyloidosis) (PSA) is a form of AL amyloidosis caused by the aggregation and deposition of insoluble amyloid fibrils derived from misfolded monoclonal immunoglobulin light chains usually produced by a plasma cell tumor and characterized by multiple organ involvement. Also known as: systemic AL amyloidosis, systemic Immunoglobulin Light chain amyloidosis, systemic amyloidosis.