There is no international consensus regarding how to assess and treat patients with immunoglobulin M (IgM)-anti-myelin-associated-glycoprotein (MAG) monoclonal gammopathy associated peripheral neuropathy. The purpose of the IMAGiNe study-Lyon/Bicêtre is to prospectively collect standardized clinical data of 25 patients with IgM-anti-MAG monoclonal gammopathy associated peripheral neuropathy in order to participate in the international IMAGiNe Study.

The main objective is to describe in detail the various clinical subtypes, clinical course, treatment responses, antibody titers of IgM-anti-MAG monoclonal gammopathy associated peripheral neuropathy using a variety of outcome measures. The obtained observational data will allow the construction of an IgM monoclonal gammopathy associated peripheral neuropathy-specific Rasch-built overall Disability Scale (RODS) that should fulfill all modern clinimetric requirements, including cross-cultural validity. The coordinating centers for the IgM-RODS construction will be the Maastricht University Medical Center and University Medical Center Utrecht, both in the Netherlands.

Inclusion Criteria:

• fulfilling the international criteria for the diagnosis Immunogloblin M (IgM) monoclonal gammopathy, with anti-myelin-associated-glycoprotein (MAG) antibodies, and peripheral neuropathy.
• age of 18 years or older followed in neuromuscular department of Lyon;
• informed consent given by the participant

Exclusion Criteria:

• concomitant diseases possibly interfering with peripheral nerve and function, as well as physical functioning, such as diabetes, renal insufficiency, (prior) treatment with chemotherapy for diseases other than their Immunogloblin M (IgM) monoclonal gammopathy associated peripheral neuropathy, history of hereditary neuropathy, vitamin deficiency, connective tissue disorder, hepatitis B and C and human immunodeficiency virus (HIV) infection, alcohol abuse (more than 5 International Units(IU)/day);
• an active malignancy with poor prognosis, undergoing treatment aside from monoclonal gammopathy associated peripheral neuropathy;
• pregnant;
• the use of any medication that may cause peripheral nerve function

Patients at least 18 years old fulfilling the international criteria for Immunogloblin M (IgM)-anti-myelin-associated-glycoprotein (MAG) monoclonal gammopathy and peripheral neuropathy