I262T, an EA1-associated mutation of a highly conserved residue at the S3 transmembrane segment of the Kv1.1 α subunit, was originally identified from a 10-year-old girl with atypical phenotypes such as distal weakness, paresis of foot extensors, and prolonged limb stiffness (neuromyotonia) lasting up to 12 hours31. This evidence concerns the gene KCNA1 and Isaacs syndrome.