Multiple Myeloma, Hyperviscosity, Hemodialysis Filter Clogging, and Antigen Excess Artifact: A Case Report

Kidney involvement in multiple myeloma can result in kidney failure. Unlike Waldenstro euro m macroglobulinemia, hyperviscosity syndrome is a rare occurrence in multiple myeloma. Timely detection of hyperviscosity syndrome and initiation of plasma exchange to remove paraproteins can significantly alter the clinical course and be potentially lifesaving. We report a case of hospitalized patient with kidney failure due to multiple myeloma not in remission who experienced shortened hemodialysis sessions due to early dialysis filter failure due to hyperviscosity, which was later corrected with plasmapheresis. When confir-mation of high levels of serum free light chains (sFLCs) was attempted, sFLC was initially reported as "not detectable." This false-negative result reflected a laboratory artifact caused by a high abundance of sFLCs, known as antigen excess or hook phenomenon. Manual serial dilutions led to unmasking of markedly elevated kappa light chain levels. This case exemplifies that patients with multiple myeloma can exhibit clinically challenging kidney manifestations even after becoming dialysis dependent. (C) 2021 The Authors. Published by Elsevier Inc. on behalf of the National Kidney Foundation, Inc.