TTN and Ventricular arrhythmia: In Family 8 (Figure 2) we found variants of unknown pathogenicity in the inward-rectifier potassium channel gene (KCNJ2) and titin gene (TTN), and another variant in the ryanodine receptor 2 gene (RYR2) which, although also considered of unknown pathogenicity, could contribute to the ventricular arrhythmia phenotype in the presence of other disease-causing variants such as the PKP2 variant.