Myelin-Associated Glycoprotein Autoantibodies, IgM, Serum

Clinical Use

Use

Autoantibodies directed against myelin-associated glycoprotein (MAG) are associated with sensory motor demyelinating peripheral neuropathy. A distal acquired demyelinating symmetric (DADS) neuropathy phenotype is the most commonly associated presentation. Patients typically have a slowly progressive symmetric sensory ataxia with/without distal weakness and an IgM monoclonal gammopathy of undetermined significance. Nerve conduction studies typically demonstrate a characteristic progressive sensory predominant mixed axonal and demyelinating neuropathy with reduced distal conduction velocities that are greater distally. In general, patients with a DADS neuropathy show limited treatment responses to intravenous immunoglobulin, and more aggressive immunotherapy may be needed.

Special Instructions

Not provided.

Limitations

This test is not diagnostic and should be interpreted in the correct clinical context. Myelin-associated glycoprotein antibodies may be found in those without neuropathy, IgM M-protein, or paraproteinemic neuropathy. MAG antibodies are present in approximately 50% to 70% of those with an IgM M-protein and a DADS neuropathy phenotype. However, MAG antibodies may also be identified in individuals with an IgM M-protein and a chronic inflammatory demyelinating polyneuropathy (CIDP) presentation as well as in other IgM paraproteinemic disorders that present with neuropathy, including myeloma, lymphoplasmacytic lymphoma (Waldenstrom macroglobulinemia), and amyloid light chain (AL)-IgM primary amyloidosis.

Test Details

New York Approved