Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), polyneuropathy associated with IgM monoclonal gammopathy with antibodies against myelin-associated glycoprotein (MAG) and Charcot-Marie-Tooth (CMT) 1a and 1b are acquired and genetic neuropathies that alter the myelin sheath as a common feature. Here, MAG is linked to monoclonal gammopathy.