Serum Free Light Chain Difference and β 2 Microglobulin Levels Are Risk Factors for Thromboembolic Events in Patients With AL Amyloidosis

Background AL amyloidosis might increase the risk of thromboembolism and other plasma cell dyscrasias; however, only a few reports have described the clinical features of thromboembolism. The present study aimed to elucidate the clinical features of thromboembolic events and to identify the risk factors for these events. Materials and Methods The medical records were retrospectively reviewed to define the clinically significant thromboembolic events. Results A total of 106 patients with biopsy-proven AL amyloidosis were included. During a median follow-up of 18.1 months (range, 0.4-166.9 months), 13 thromboembolism events were identified in 13 patients. Of the 13 patients, 9 (8.5%) experienced acute cerebral infarction, 2 (1.9%) experienced pulmonary embolism, and 2 (1.9%) experienced deep vein thrombosis. Patients with a higher serum free light chain (FLC) difference (≥ 172.4 mg/L) or β 2 -microglobulin (β2MG) levels (≥ 2.78 mg/L) experienced significantly more thromboembolic events compared with those with a lower value according to multivariable analysis (for FLC difference: hazard ratio, 4.309; 95% confidence interval, 1.158-16.032; P = .029; for β2MG: hazard ratio, 9.739; 95% confidence interval, 1.127-84.174; P = .039). Most thromboembolic events (11 of 13; 84.6%) occurred within the first year after the AL amyloidosis diagnosis. Conclusion The incidence of thromboembolism was substantial in those with AL amyloidosis. A greater FLC difference and for β2MG levels were risk factors for thromboembolic events.