Abstract : Solitary bone plasmacytoma (pso) is a rare tumor, made of malignant plasma cells observed in a single bone, and without systemic proliferation. We report the case of a 33 year-old man who was admitted with chronic demyelinating sensorimotor polyneuropathy. Immunoelectrophoresis with immunofixation of serum proteins showed a monoclonal peak igg with lambda light chain and the workup was in favour of right hipbone secreting solitary plasmacytoma. The patient was treated with radiotherapy and steroids, and the evolution has been marked by a partial recovery of the motor deficit. An acute demyelinating sensorimotor polyneuropathy has often been described in association with pso. However, subacute and chronic demyelinating polyradiculoneuropathies have rarely been described in such patients with pso.the diagnosis should differentiate pso, poems and multiple myeloma.