Studies of the hyperviscosity syndrome. II. Macroglobulinemia.

Thirty-four patients with macroglobulinemia were studied for the incidence of hyperviscosity syndrome (HVS) and the circumstances in which this complication occurred. The following were evaluated: total serum protein, quantity of IgM paraprotein, and relative serum viscosity. These measurements were coupled with physical-chemical studies of isolated IgM proteins, including molecular weight and evaluation of molecular shape, by determination of intrinsic viscosity, viscosity increment, ratio of frictional coefficient, and coefficient of concentration dependence. It was found that relative serum viscosity values in the symptomatic range (above 6.0) were present in 38 per cent of the patients and were usually associated with IgM values greater than 5.0 gm. per 100 ml. All IgM proteins studied were large, hydrodynamically active molecules. A patient who developed HVS with IgM values below 3.5 gm. per 100 ml. had markedly asymmetrical molecules. The principal factors in the pathogenesis of this syndrome in macroglobulinemia are the concentration and molecular shape of IgM. Additional factors include protein-protein interactions between IgM and serum constituents.