Pathophysiology
Clinical meaning
Waldenstrom macroglobulinemia (WM, lymphoplasmacytic lymphoma) is an indolent B-cell neoplasm characterized by bone marrow infiltration with lymphoplasmacytic cells that produce monoclonal IgM immunoglobulin. The MYD88 L265P mutation is present in greater than 90% of WM cases, constitutively activating NF-kB and JAK-STAT signaling pathways that drive tumor cell survival and proliferation. The hallmark clinical feature is hyperviscosity syndrome, caused by the pentameric structure of IgM (molecular weight 900 kDa) that dramatically increases blood viscosity at relatively modest concentrations. Hyperviscosity impairs microcirculation, producing neurological symptoms (headache, blurred vision, dizziness, ataxia, confusion), visual disturbances (sausage-link retinal veins, retinal hemorrhages on fundoscopy), and mucosal bleeding (epistaxis, gingival bleeding). Additional features include peripheral neuropathy (anti-MAG IgM antibodies causing demyelination), cold agglutinin disease (IgM acting as a cold-reactive autoantibody against red blood cells), cryoglobulinemia, and amyloidosis. The nurse monitors for signs of hyperviscosity, assesses visual acuity and performs fundoscopic assessment, assists with emergent plasmapheresis for symptomatic hyperviscosity (immediate viscosity reduction), monitors CBC for cytopenias, administers chemotherapy (rituximab-based regimens) as prescribed, monitors for transfusion reactions (avoid packed RBCs when viscosity is critically elevated), and assesses for peripheral...