Anti-IgM to myelin-associated glycoprotein

Myelin-associated glycoprotein (MAG) belongs to the cell adhesion molecules and it is expressed with oligodendrogliocytes and Schwann cells. It is a mediator of oligodendrogliocytes interactions to each other and neurons. When axons are myelinated, it is also found on their outer surfaces and adjacent surfaces of myelin-forming cells.  IgM antibodies react to oligosaccharides (HNK-1 epitope) glycolipids and glycoproteins concentrated in peripheral nerves in most  neuropathy patients. This epitope is shared by a number of other neuropathic target antigens (eg. gangliosides). Anti-MAG antibodies are associated to IgM gammopathy.  Paraproteinemic demyelinating neuropathy (PDN) is an antibody-mediated demyelinating neuropathy. The clinical findings are distinguished with distal and symmetrical, mainly sensory neuropathy. Monoclonal immunoglobulin M anti-MAG antibodies are exclusive for this condition and it is believed to be pathological. The patientsunderwent this test to assess the  IgM neuropathy prevalence,  the incidence of 31%  has been reported. More than 50% of  peripheral neuropathy patients (hereinafter referred to as NP). Test for anti-MAG antibodies is essential to differentiate the IgM-associated NP from other commonly encountered acquired polyneuropathies such as chronic inflammatory demyelinating NP. Both disorders can progress slowly and be found during morphological and electrophysiological tests mainly as demyelinating NP. In addition,  protein concentration in the cerebrospinal fluid is increased during these diseases, and therefore this indicator can be used to assess the immunosuppressive therapy response.

In a study caried out with 112 patients, 72% of IgM antibodies have ben specific for neural tissue: 52% of them were directed against MAG or cross-reacting glycolipid SG [L] PG (sulfoglucuronyl [lactazaminyl] paraglobozide) and 22% reacted to gangliosides.  EFNS / PNS PDN Management (Joint Working Group of the European Federation of Neurological Societies (EFNS) and Peripheral Neurological Societies (PNS)) have developed clinical guidelines to diagnose, examine and treat the paraproteinemic demyelinating neuropathy patients.

Indications for test

Marker for anti-MAG / SGPG IgM monoclonal gammopathy associated neuropathy

• Differential diagnosis of polyneuropathy

Interpretation of results

High level

1. Anti-MAG / SGPG IgM monoclonal gammopathy associated neuropathy;
2. Chronic inflammatory demyelinating polyneuropathy (CIDP)