Supplementary Material for: Lack of Any Cardiac Involvement in a Patient with Andersen-Tawil Syndrome Associated with the c.574A→G Mutation in <i>KCNJ2</i>

The Andersen-Tawil syndrome (ATS) is characterized by hypo-normokaliemic muscle periodic paralysis, dysmorphic features and ventricular arrhythmias. Most cases are caused by mutations in <i>KCNJ2,</i> encoding for the potassium inwardly rectifying channel, Kir2.1 (ATS1). Although <i>KCNJ2</i> mutations show no obvious genotype-phenotype correlations and incomplete penetrance, signs of cardiac involvement are usually present in most ATS1 cases. In contrast, here we describe an Italian ATS1 patient, carrying a c.574A→G mutation in <i>KCNJ2,</i> who had both facial dysmorphisms and muscle periodic paralysis but who did not manifest any cardiac involvement, although the same mutation was originally described in a Japanese kindred, in which all affected individuals manifested a severe cardiac phenotype.