Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease that affects predominantly the right ventricle and cause sudden cardiac death. We studied 156 ARVC patients lacking variants in known ARVC genes, and identified two unique FLNCtv variants in two families fulfilling “definite” diagnosis according to the 2010 ARVC Task Force Criteria. Segregation analysis revealed that one of them was a de novo variant. In both families the disease phenotype was characterized by prominent ventricular arrhythmias and sudden cardiac arrest. Our findings should prompt inclusion of FLNC genetic testing in ARVC to improve diagnostic yield and testing of at-risk relatives. (By Prof. Luisa Mestroni, https://jmg.bmj.com/content/early/2020/01/10/jmedgenet-2019-106394 )