Monoclonal Gammopathy of Undetermined Significance

Abstract

In their long-term follow-up study of patients with monoclonal gammopathy of undetermined significance (MGUS), Kyle et al. (Feb. 21 issue)¹ did not include patients with pure Bence Jones proteinuria, resulting from a plasma-cell dyscrasia involving the excretion of monoclonal light chains into the urine. From a pathophysiological point of view, it is reasonable to include light-chain disease in MGUS, since it clearly also represents a gammopathy.² Although the disorder is clinically relevant, there is astonishingly little information in the literature on the prognosis for patients with pure, idiopathic Bence Jones proteinuria.^3,4 Before 1980, it was not recognized that there are indolent cases in which Bence Jones proteinuria remains stable for years,² thus representing a benign counterpart of light-chain myeloma with its poor prognosis. In 1982, seven patients with idiopathic Bence Jones proteinuria, five of whom had progression to myeloma, were described in detail by Kyle and Greipp.³ Clinical information on a larger series of patients with pure Bence Jones proteinuria (which should certainly be available at the Mayo Clinic³) would permit a reliable estimate of the prognosis. Therefore, we wonder about the incidence of Bence Jones MGUS in the group of patients who were followed at the Mayo Clinic, the authors' approach to the treatment of these patients, and the natural course of the condition.