Evaluation of hyperviscosity in monoclonal gammopathies.

The serum or plasma hyperviscosity syndrome has been described in both monoclonal and polyclonal immunoglobulin disorders. The usefulness of initial and serial plasma viscosity measurements by an automated viscometer technique was evaluated and compared with serum protein electrophoresis data in 107 patients without monoclonal gammopathies and 153 patients with monoclonal gammopathies. In patients without monoclonal gammopathies, plasma viscosity correlated best with the concentration of gamma globulins. In patients with monoclonal gammopathies, plasma viscosity correlated best with the serum monoclonal protein concentration, but individual patient variations in the ratio of plasma viscosity to monoclonal protein concentration made accurate prediction of plasma viscosity difficult without direct measurement. Six of eight patients with plasma viscosity above 5.0 cp had classic symptoms of hyperviscosity syndrome, and four of the six had recurrent episodes. Six other patients with plasma viscosity above 4.0 cp had more subtle presentations of hyperviscosity but responded equally well to therapeutic lowering of plasma viscosity. These patients are part of a larger subset of 27 patients in whom initial plasma viscosity was above 3.0 cp. No patient with an initial plasma viscosity below 3.0 cp subsequently showed hyperviscosity symptoms. Plasma viscosity measured by this technique is a useful tool in screening patients with dysproteinemias to identify and monitor those with and at risk for the hyperviscosity syndrome.