Monoclonal gammopathy associated neuropathy: Focusing on IgM M-protein associated neuropathy

Monoclonal gammopathy associated neuropathies are a complex and difficult to classify group of disorders. A causal relationship has only been determined between the IgM monoclonal protein (M-protein) and neuropathy; this disease is being referred to as IgM M-protein associated neuropathy. It is a late-onset, male-predominant, slowly progressive, symmetric, predominantly sensory ataxic neuropathy with relatively mild or no weakness. There is strong evidence for a pathogenic role of IgM antibodies in neuropathy development, with approximately 50%-60% of patients having high titers of antimyelin associated glycoprotein (anti-MAG) antibodies. The neuropathy is primarily demyelinating with strong evidence for electrophysiological features reflecting length dependency. Treatment choices are influenced by the burden of the disease and evidence for treatment benefit. Strong evidence for treatment benefit is lacking due to shortcomings in study designs. However, there is low to moderate quality evidence that rituximab is of benefit in the treatment of IgM M-protein associated neuropathy.