Hyperviscosity Syndrome



  • Hyperviscosity syndrome (HVS) is the clinical consequence of increased blood viscosity
  • The classic clinical symptoms are the triad of mucosal bleeding, visual disturbances, and neurologic signs
  • Viscosity is the resistance a material has to change in form
  • The higher the blood viscosity, the more the internal resistance to blood flows
  • Increased cardiac output is required to provide adequate perfusion of hyperviscous blood
  • Oxygen delivery is impaired as transit through the microcirculatory system slows. This impaired microcirculatory oxygenation gives rise to the clinical symptoms of this syndrome


  • Hyperviscosity occurs when there is elevation of either the cellular or acellular components of circulating blood
  • Acellular (protein) hyperviscosity:
    • The most common cause (85–90%) of hyperviscosity is increased concentration of γ globulins:
      • Monoclonal gammopathies: From malignant diseases like Waldenstrom macroglobulinemia and multiple myeloma
      • Polyclonal gammopathies: Usually rheumatic diseases (very rare)
  • Cellular (blood cell) hyperviscosity:
    • Much less common (10–15%)
    • Increased numbers of RBC, as in polycythemia vera
    • Increased concentration (>100,000) of WBC, as in acute and chronic leukemia
    • Thrombocytosis

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