Dominant-negative mutations in the KCNJ2 gene, encoding the K+ channel Kir2.1, also cause primary HypoPP in Andersen-Tawil syndrome, a disorder clinically distinct from HypoPP1 and 2 since the neuromuscular phenotype is associated with cardiac arrhythmia and bone deformities (Plaster et al., 2001). Here, KCNJ2 is linked to Andersen-Tawil syndrome.