Risk factors for hematological malignancy in polyneuropathy associated with monoclonal gammopathy.

Polyneuropathy associated with monoclonal gammopathy of undetermined significance (MGUS) is a well-known disease entity. Of the patients with monoclonal gammopathy without neuropathy, 25% develop a hematological malignancy during long-term follow-up. Whether the frequency of hematological malignancy is similar in patients with polyneuropathy associated with monoclonal gammopathy and whether hematological screening is necessary in these patients is unknown. To determine the frequency of and risk factors for a hematological malignancy, we investigated 104 patients with polyneuropathy and monoclonal gammopathy. Potential diagnostic variables were obtained from medical history, physical and neurological examination, and laboratory analysis. The associations between potential diagnostic variables and outcome, hematological malignancy, were evaluated by univariable and multivariable logistic-regression analysis. Among our patients, 23 had a hematological malignancy (8 multiple myeloma, 10 low-grade lymphoma, 3 plasmacytoma, 1 Castleman's disease and 1 POEMS syndrome [polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes]). Weight loss, progression of the neuropathy, and an M-protein level > 1 g/L were independent risk factors for malignancy. Extensive screening is indicated in patients with these features.