We present the case of a 31 year-old male patient, who presented polyneuropathy, symmetrical, ascending, and progressive, that led to prostration of eight months duration, accompanied by hypogonadism, hypothyroidism, hyperprolactinemia, and the presence of multiple erythematous nodules on the skin. The MRI showed hypointense lesions in the vertebrae T-6 and L-4 with sclerotic appearance. The bone marrow biopsy reported the presence of 12% plasma cells with lambda restriction, supporting monoclonal gammopathy (plasmocytoma).