[Clinical Analysis of Patients with MGUS, Primary Light Chain Amyloidosis, Multiple Myeloma or Multiple Myeloma with Concurrent Amyloidosis].

Objective: To summarize and compare the clinical baseline characteristics of patients with monoclonal gammopathy of undetermined significance (MGUS), primary light chain amyloidosis (pAL), multiple myeloma (MM), or MM with concurrent amyloidosis, especially the differences in cytogenetic abnormalities.

Methods: The clinical data of 15 cases of MGUS, 34 cases of pAL, 842 cases of MM and 23 cases of MM with concurrent amyloidosis were analyzed and compared retrospectively.

Results: Cytogenetic statistics showed that the incidence of t (11; 14) in the four groups (MGUS vs pAL vs MM vs MM with concurrent amyloidosis) was 0%, 33.3%, 16.4%, and 15.8%, respectively (P=0.037); that of 13q deletion was 20.0%, 14.7%, 45.8% and 56.5%, respectively (P<0.001); gain of 1q21 was 50.0%, 12.5%, 47.4% and 40.9%, respectively (P=0.001). Proportion of pAL patients with 0, 1 and≥2 cytogenetic abnormalities (including 13q deletion, 17p deletion, 1q21 amplification and IgH translocation) accounted for 41.9%, 41.9% and 16.1%, respectively; while the proportion of the same category in MM was 17.6%, 27.3%, and 55.2% respectively; this ratio of MM with concurrent amyloidosis was more similar to MM. Subgroup analysis showed that genetic abnormalities (including 13q deletion, 17p deletion and 1q21 amplification) were comparable within t (11; 14) negative and positive groups. Compared with positive cases, t(11; 14) negative patients with MM or MGUS were more likely to have 13q deletions and multiple genetic abnormalities.

Conclusion: Clinical characteristics of pAL, especially cytogenetic abnormalities, are significantly different from MM with concurrent amyloidosis. It suggests that although the onset characteristics are similar, actually the two diseases belong to different disease subtypes which should be carefully predicted and identified.