[Neuropathies associated with monoclonal IgM anti-MAG antibodies]

Monoclonal IgM anti-MAG associated peripheral neuropathies are part of demyelinating dysimmune peripheral neuropathies. The hematological disease probably does not influence the outcome of the neuropathy. Neuropathies associated with IgM anti-MAG antibodies are predominantly sensory and distal polyneuropathies associated with ataxia, unsteadiness and tremor. The neurophysiological features include a symmetric sensorimotor demyelinating neuropathy with more slowing of conduction in the distal than in the proximal nerve segments, a length-dependence, and a variable degree of denervation. High titers of IgM anti-MAG antibodies confirm the diagnosis. The natural history is mostly slow with mild to moderate functional impairment. However, some patients have a faster evolution associated with a more severe handicap. Immunotherapies studies have failed to demonstrate significant efficacy of these treatments. Furthermore, severe adverse effects are not uncommon with any of these therapies. Thus, the risk of possible severe adverse effects must be balanced against any possible benefits. More research is needed to improve the management of anti-MAG neuropathies: research on treatment, on prognostic factors, and development of specific assessment scales adapted to the particularities of anti-MAG neuropathies.