Infection as a trigger of acute, transient glomerular deposition of clonal immunoglobulins

Glomerular deposition of monoclonal IgM, frequently in the form of intracapillary pseudothrombi, can be seen in Waldenström macroglobulinemia (WM) and type I cryoglobulinemia (CG). They are typically associated with plasma cell or B-lymphoid neoplasms, particularly lymphoplasmacytic lymphoma (LPL). While infection is a frequent trigger of mixed (type II and III) CG, its association with type I CG is uncommon. We report two cases in which striking lambda-chain-restricted IgM deposits and acute kidney injury (AKI) occurred in the setting of known or suspected systemic infections, with prompt resolution on treatment of the infection.