Light Chain Disorders Associated with COVID-19 Vaccines

Serum free light chain (sFLC) elevation following SARS-CoV-2/COVID-19 infection/illness and COVID-19 mRNA vaccination may indicate adverse immunological responses, such as clonal proliferation or inflammation. (Malecka-Gieldowska, 2021, Gudowska-Sawczuk, 2022) To evaluate the use of sFLC measurements, the Vaccine Adverse Event Reporting System (VAERS), maintained by the Centers for Disease Control and Prevention and the Food and Drug Administration, was searched for sFLC abnormalities following COVID-19 vaccination. Seventy-five (75) cases were identified that as having free light chain disorders following at least one injection of COVID-19 vaccine. Twenty-five cases (33%) had complete quantitative data for serum kappa (sFLCk) and lambda (sFLCλ) and kappa/lambda ratio (sFLCR) and are the subject of this paper. Six patterns of sFLC elevations were identified. Case reports are given as examples. Based on this study careful evaluation of out of range values for sFLCk and/or sFLCλ is advisable even when sFLCR is within normal range. FLC measurements should be further evaluated as a tool to guide clinical diagnosis and to monitor inflammatory and neoplastic disease activity.