Which initial investigations should I perform to assess for amyloidosis in a patient with suspected systemic involvement?

Initial investigations to assess for amyloidosis with suspected systemic involvement include:

• Serum and urine protein electrophoresis with immunofixation to detect monoclonal proteins, as amyloidosis is often related to plasma cell dyscrasias such as multiple myeloma.
• Serum-free light-chain assay and serum-free light-chain ratio to identify light-chain amyloidosis and assess prognosis.
• Bone marrow aspirate and trephine biopsy with plasma cell phenotyping to confirm clonal plasma cell disorders contributing to amyloid deposition.
• Imaging such as whole-body MRI or low-dose CT to assess for bone involvement or organ infiltration.
• Biopsy of affected tissue (e.g., abdominal fat pad, involved organ) for histological confirmation of amyloid deposits using Congo red staining.

These investigations align with the diagnostic approach for plasma cell disorders and systemic amyloidosis, as amyloidosis is frequently associated with monoclonal gammopathies and systemic involvement requires assessment of organ function and extent of disease NICE NG35,NICE CKS.