Immunophenotypic analysis of abnormal plasma cell clones in bone marrow of primary systemic light chain amyloidosis patients

Background Primary systemic light chain amyloidosis (AL) is a rare plasma cell disease, our purpose was to analyze the immunophenotypic characteristics of the plasma cells in bone marrow in AL patients, and explore whether the detection of abnormal plasma cell clones in bone marrow by flow cytometry (FCM) could be used as an important indicator of AL diagnosis. Methods Fresh bone marrow samples were collected from 51 AL, 21 multiple myeloma (MM), and 5 Waldenstrom's macroglobulinemia (WM) patients. The immunophenotype of bone marrow cells were analyzed and compared by FCM using a panel of antibodies including CD45, CD38, CD138, CD117, CD56, and CD19. Results In AL, light chain restriction could be identified in 31 cases (60.9%), in which the A light chain restriction was found in 24 cases (77.4%). In MM, K light chain restriction was found in 13 cases (61.9%), and A light chain restriction in eight cases. CD45 on abnormal plasma cells was negative to weakly positive in both AL and MM, but was positive to strongly positive in WM. In the bone marrow plasma cells of the 51 AL, 78.4% were CD56+, 68.6% were CD117+, and 88.2% were CD19- While in the 21 MM cases, 66.7% were CD56+, 38.1% were CD117+, and 90.4% were CD19. The plasmacytoid lymphocytes in the five WM patients were CD19+ and CD56-, CD117-. Conclusion Detection of abnormal plasma cell clones in bone marrow by FCM is valuable for the diagnosis of AL.