Anti-myelin-associated glycoprotein antibodies predict the development of neuropathy in asymptomatic patients with IgM monoclonal gammopathy

We examined 52 asymptomatic patients with IgM monoclonal gammopathy and correlated anti-myelin-associated glycoprotein (anti-MAG) IgM with the presence of subclinical neuropathy and, in 24 of these patients, with the development of symptomatic neuropathy during a follow-up interval of 40 to 144 months (mean, 75.3 months). Three of 6 patients (50%) with high (>1/6,400) anti-MAG IgM had subclinical neuropathy at entry compared with 2 of 46 patients (4.3%) with low or no reactivity. At follow-up, a symptomatic neuropathy occurred in 3 of 4 patients with high reactivity and in 3 of 21 patients with low or no reactivity. The correlation of high anti-MAG IgM with the presence of subclinical neuropathy or the development of symptomatic neuropathy supports its pathogenetic role in the neuropathy.