[Successful treatment with rituximab in two cases of IgM-monoclonal gammopathy of undetermined significance (MGUS) neuropathy].

A 66-year-old male was hospitalized with muscle weakness and gait disturbance. Examination revealed IgM 3,407 mg/dl (IgM, κ-type M protein) and he was diagnosed as having IgM-MGUS neuropathy. He suffered from paralysis of respiratory muscles and required a respirator support. Plasmapheresis and intravenous immunoglobulin were performed and he was weaned from the respirator. Rituximab given as 8 weekly infusions improved gait disturbance. A 71-year-old male was hospitalized with lumbago, numbness of lower extremities and gait disturbance. Examination revealed IgM 1,553 mg/dl (IgM, λ-type M protein) and he was diagnosed with IgM-MGUS neuropathy. Rituximab given as 8 weekly infusions improved gait disturbance. It was concluded that rituximab is a well-tolerated treatment that may be effective in some patients with IgM-MGUS neuropathy.