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MORBIDITY MEDIATED BY THE EFFECTS OF IGM

Hyperviscosity Syndrome

Blood hyperviscosity is affected by increased serum IgM levels leading to hyperviscosity-related complications.[41] The mechanisms behind the marked increase in the resistance to blood flow and the resulting impaired transit through the microcirculatory system are rather complex.[41–43] The main determinants are (1) a high concentration of monoclonal IgMs, which may form aggregates and may bind water through their carbohydrate component, and (2) their interaction with blood cells. Monoclonal IgMs increase red cell aggregation (rouleaux formation, see Fig. 88-2) while also reducing deformability. The possible presence of cryoglobulins can contribute to increasing blood viscosity as well as to the tendency to induce erythrocyte aggregation. Serum viscosity is proportional to IgM concentration up to 30 g/L, then increases sharply at higher levels. Increased plasma viscosity may also contribute to inappropriately low erythropoietin …