The hyperviscosity syndrome. I. In IgG myeloma. The role of protein concentration and molecular shape.

The hyperviscosity syndrome is an uncommon complication in IgG myeloma. Its occurrence has been ascribed to the presence in the serum of high molecular weight polymers of the IgG proteins. Three patients with IgG myeloma and the clinical hyperviscosity syndrome were investigated, none of whom had IgG polymers in the serum by analytical ultracentrifugation. Relative serum viscosity in these patients ranged from 10 to 17.4 (normal 1.4-1.8). The total serum proteins ranged from 14 to 19 g/100 ml of which 10 to 17 g/100 ml was IgG globulin. Physicochemical studies of two of the isolated myeloma proteins indicated that they were of normal molecular weight (near 158,000 and 162,000). Protein Ca had a normal molecular radius (52.2 A) and configuration, (intrinsic viscosity of 5.5 cc/g, frictional ratio 1.48), but was present in very high concentration in the serum. Protein Pur had an increased molecular radius (58.2 A) and was asymmetrical (intrinsic viscosity 10.2 cc/g, frictional ratio 1.63). These results indicate that the concentration and molecular configuration of the myeloma protein are important determinants of the presence or absence of the hyperviscosity syndrome.