[Antibodies directed to voltage-gated potassium channels in sera from acquired neuromyotonia and related disorders].

Anti-voltage-gated potassium channel (VGKC) antibodies were measured in sera from 21 patients with acquired neuromyotonia (Isaacs syndrome) and related disorders. Seventeen of 21 sera suppressed potassium currents of neuroblastoma cell line (NB-1) using the patch clamp method, and the finding is mostly correlated with myokymic discharge in electromyography. Regarding the pathophysiology of suppression of VGKC, we investigated the effects of sera from 2 ANM patients on channel kinetics using the patch clamp method. The activation and inactivation kinetics of the potassium current were not altered by patients' immunoglobulins. We also investigated the effect of patients' sera on different VGKC subtypes using hKv1.1 and 1.6 transfected CHO cells. The same patients' sera suppressed the expressed VGKCs. Our results suggest that anti-VGKC antibodies may be positive not only in patients with classical ANM (Isaacs syndrome) but also in patients with related disorders who did not fulfill the characteristic symptoms. These disorders may be categorized as potassium channelopathy of the peripheral nervous system. The pathophysiology of the suppression of VGKC by antibodies is not the direct effect on channel kinetic but due to increased degradation or reduced production of VGKC. Epitopes of Anti-VGKC antibodies are still unclear.