Mutations in the KCNJ2 gene, which encodes the alpha‐subunit of the potassium channel Kir2.1, are identified in about 60% of ATS cases, which are classified as Andersen–Tawil syndrome type 1 (ATS1), and approximately 30% of these are de novo mutations (Nguyen, Pieper, & Wilders, 2013). Here, KCNJ2 is linked to Andersen-Tawil syndrome.