Mutations in the KCNJ2 gene, encoding the inwardly rectifying K+ channel Kir2.1, are responsible for the rare Andersen-Tawil syndrome (OMIM 170390), a condition characterized by periodic paralysis, cardiac arrhythmia and skeletal abnormalities (1). The gene discussed is KCNJ2; the disease is Andersen-Tawil syndrome.