Lack of any cardiac involvement in a patient with Andersen-Tawil syndrome associated with the c.574A→G mutation in KCNJ2

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 KCNJ2, encoding for the potassium inwardly rectifying channel, Kir2.1 (ATS1). Although KCNJ2 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 KCNJ2, 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.