Hyperviscosity Syndrome

Basics

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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