IgM-containing fraction suppressed voltage-gated potassium channels in acquired neuromyotonia.
OBJECTIVE
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.


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.


RESULTS
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.


CONCLUSIONS
Anti-VGKC antibodies belonging to the IgM subclass should be determined in seronegative ANM patients.
Kurono
A
A
Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medicine and Dental Sciences, Kagoshima, Japan.
Arimura
K
K
Watanabe
O
O
Tomimitsu
H
H
Nagado
T
T
Sonoda
Y
Y
Kameyama
M
M
Osame
M
M
D000917:Antibody Formation; D016022:Case-Control Studies; D006801:Humans; D007075:Immunoglobulin M / Q000032:analysis*; D020386:Isaacs Syndrome / Q000276:immunology* / Q000503:physiopathology*; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000276:immunology* / Q000502:physiology*
D007075:Immunoglobulin M; D024642:Potassium Channels, Voltage-Gated