Correlation between cytomegalovirus infection and IgM anti‐MAG/SGPG antibody–associated neuropathy

IgM anti-myelin-associated glycoprotein (anti-MAG)/sulfated glucuronyl paragloboside (SGPG) antibody is found in some patients with chronic polyneuropathy (CP). An antigen-driven process is considered to induce this autoantibody, but the agent has yet to be identified. It has been reported that sera from cytomegalovirus (CMV)-infected patients contained anti-SGPG antibody. To clarify the mechanism of the production of the anti-MAG/ SGPG antibody, we investigated CMV DNA in sera from 26 patients with IgM anti-MAG/SGPG antibody-positive CP. Twenty-three (88%) had CMV DNA. The positive frequency was significantly higher than the frequencies in sera from patients with IgM anti-MAG/SGPG-negative CP, the other disease controls, and the normal control subjects. There were no statistical differences in the frequencies of Epstein-Barr virus DNA between anti-MAG/ SGPG-positive and anti-MAG/SGPG-negative CP and between anti-MAG/SGPG-positive CP and each disease control. Moreover, no herpes simplex virus 1 DNA was detected in the sera from patients with anti-MAG/SGPG-positive CP. The strong correlation of anti-MAG/SGPG-positive CP with the presence of serum CMV DNA suggests that CMV infection induces the IgM anti-MAG/ SGPG antibody.