Waldenstrom's macroglobulinemia, a hyperviscosity manifestation of venous stasis retinopathy.

Waldenstrom's macroglobulinemia is characterized by hyperviscosity. This is usually the result of an increased serum concentration of IgM molecules; this paraprotein has a high molecular weight and unusual shape. The changes in shear rate associated with increased IgM concentrations produces maximal viscosity in the venous circulation. One of the major causes of retinal venous occlusion is venous stasis retinopathy. The typical patient with this disorder is a young individual with a periphlebitis.. However, the hyperviscosity in Waldenstrom's macroglobulinemia is an ideal representative of a venous stasis that is without associated vascular pathology. To illustrate this situation, two cases are described and their etiologic features are discussed.