The Andersen-Tawil Syndrome (ATS) is a rare ion channelopathy caused by dominant loss-of-function mutations of a ubiquitously expressed inward rectifier K channel (Kir2.1) that presents with periodic paralysis, cardiac dysrhythmia, and skeletal dysmorphia. Episodes of weakness in ATS are hours to days in duration and are often provoked by exercise, stress, cold, or changes in serum K. The K-induced attacks are usually in the setting of hypokalemia but have also been reported with hyperkalemia. To explore the function basis of episodic weakness in ATS, we developed murine models based on either a conditional knockout of Kir2.1 or pharmacologic block.  These models show susceptibility to high-K induced loss of force when the Kir conductance is < 30% of normal, and with further reduction to < 10% then low- or high-K elicits weakness.
[General reference about ATS]
Nikki M. Plaster et al (2001) Mutations in Kir2.1 Cause the Developmental and Episodic Electrical Phenotypes of Andersen’s Syndrome. Cell 105: 511–519