Systemic blood hyperviscosity syndrome

Specialty: Hematology.

• Plasma or cellular hyperviscosity
• elevated serum viscosity syndrome

Why it occurs

• Waldenström macroglobulinemia (lymphoplasmacytic neoplasia characterized by the uncontrolled production of a large monoclonal immunoglobulin M that exponentially alters blood rheology)
• IgA or IgG-secreting multiple myeloma (especially in polymeric forms of IgA or extremely high concentrations of IgG that form macromolecular aggregates)
• Acute myeloid leukemia with hyperleucytosis / Extreme leukemoid reaction (numbers of blasts or circulating leukocytes greater than 100,000/μL that increase cell viscosity and cause microvascular leukostasis)
• Decompensated polycythemia vera (severely elevated hematocrit >55-60% with massive erythrocyte overload)
• Cryoglobulinemia type I (precipitation of monoclonal immunoglobulins in response to low temperatures, blocking distal microcirculation).

Initial workup

Serum protein electrophoresis and serum immunofixation to identify and quantify the monoclonal band (M peak); direct measurement of serum viscosity using Oswald viscometer (normal values ​​between 1.4 and 1.8 centipoise; symptoms of hyperviscosity typically appear with values ​​>4.0-5.0 cp); immediate complete blood count with manual cell count if leukostasis is suspected (automated counters may give false negatives or erroneous platelet readings due to cell fragments); emergency fundus examination performed by a specialist; bone marrow biopsy with immunophenotyping to characterize the underlying neoplastic population (clonal plasma cells or plasmacytoid lymphocytes).

Standard management

• Plasmapheresis / Therapeutic plasma exchange — first choice emergency procedure in cases of hyperviscosity due to IgM or IgA; quickly eliminates macromolecules from the intravascular space, significantly reducing viscosity in a single session
• Rituximab — anti-CD20 monoclonal antibody indicated in Waldenström Macroglobulinemia; It should be administered with extreme caution since it can cause a transient increase in IgM levels or "flare", requiring prior plasmapheresis if the basal viscosity is already high.
• Hydroxycobalamin / Hydroxyurea — fast-acting cytoreductive agent to reduce cell counts in polycythemia or extreme thrombocythemia
• 0.9% physiological saline solution (vigorous intravenous hydration for initial hemodilution, closely monitoring cardiovascular function to avoid acute lung edema due to volumetric overload).