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Published on: May 5, 2018
IgM-containing fraction suppressed voltage-gated potassium channels in acquired neuromyotonia
A Kurono1, K Arimura, O Watanabe
1Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medicine and Dental Sciences, Kagoshima, Japan.
Objectives:
Acquired neuromyotonia (ANM) is an autoimmune disorder caused by antibodies to voltage-gated potassium channels (VGKC). Previously, we reported a patient with immunoglobulin M (IgM), instead of immunoglobulin G (IgG), anti-VGKC antibody. The purpose of this study was to determine the function of IgM-containing fraction in ANM patients.
Materials And Methods:
We determined whether anti-VGKC antibodies in the IgG or IgM-containing fractions suppressed outward potassium current (OKC) using the patch clamp method in three patients with ANM. Whole sera from all patients suppressed OKCs.
Result:
Only the purified IgG, not the IgM-containing fractions from two patients suppressed VGKCs, whereas in a patient with IgM anti-VGKC antibody, only the IgM-containing fractions, not the IgG-containing fractions suppressed VGKCs.
Conclusion:
Anti-VGKC antibodies belonging to the IgM subclass should be determined in seronegative ANM patients.
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