Therapeutic Plasma Exchange Rapidly Restores Red Blood Cell Deformability in Waldenstr鰉 Macroglobulinemia

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma characterized by monoclonal immunoglobulin M (IgM) overproduction, leading to hyperviscosity syndrome and microvascular complications. While increased plasma viscosity is a well-recognized feature of WM, the impact of extreme IgM elevation on intrinsic red blood cell (RBC) mechanical properties remain incompletely characterized. Here, we report a case of WM with markedly elevated IgM associated with profound impairment of RBC deformability. Therapeutic plasma exchange rapidly reduced serum IgM levels, accompanied by parallel and sustained improvement in RBC deformability. Given the importance of RBC deformability in microvascular blood flow, these findings highlight a reversible, IgM-mediated alteration in RBC mechanics and provide novel insights into microcirculatory dysfunction in WM.