IgM antibodies targeting neuronal surface proteins with the human natural killer epitope, which is contained in the myelin-associated glycoprotein, previously detected in serum of patients with neuropathy and monoclonal gammopathy, have been found in P-OMS patients.[6] The role of the cell-mediated immune mechanism in the development of OMS is evidenced as well. This evidence concerns the gene MAG and opsoclonus-myoclonus syndrome.