Rapidly progressive fatal hepatic failure due to IgM-related AL amyloidosis in Waldenström's macroglobulinemia: an autopsy case report.

IgM-related AL amyloidosis is a rare and distinct clinical entity, often associated with underlying lymphoproliferative disorders such as Waldenström's macroglobulinemia (WM) or lymphoplasmacytic lymphoma (LPL). Unlike non-IgM AL amyloidosis, it exhibits unique organ involvement patterns and generally poorer prognosis. We report a 66-year-old woman diagnosed with WM complicated by systemic IgM-κ AL amyloidosis. She received combination chemotherapy with rituximab and bendamustine (BR), resulting in a reduction of serum IgM levels. Despite the hematologic improvement, her liver dysfunction rapidly progressed, and she died of hepatic failure just two months after diagnosis. Pathological autopsy revealed massive IgM-κ amyloid deposition in the liver and multiple organs, with no residual lymphoma in the bone marrow or lymph nodes. These findings suggest that extensive hepatic amyloid infiltration was already present at diagnosis, and that organ response could not be achieved despite hematologic improvement. This case highlights the aggressive nature of IgM-related AL amyloidosis and the critical importance of early detection, especially when liver dysfunction is observed. Current therapies targeting the underlying clone may not be sufficient in cases with advanced organ involvement, emphasizing the urgent need for novel strategies to facilitate amyloid clearance and protect organ function.