In patients presenting with repetitive ventricular arrhythmias (VAs), a specific pattern of left ventricular scar characterized by a subepicardial/midmyocardial ringlike distribution on cardiac magnetic resonance (CMR) has been recently associated with high risk of recurrent malignant VAs and sudden cardiac death (SCD). The genetic background and familial basis of ringlike left ventricular cardiomyopathy (RLCM) has not been previously investigated To document the results of systematic genetic evaluation of probands with RLCM and cascade clinical/genetic screening of the family members of the proband regardless of the clinical presence of VAs Clinical, CMR and genetic evaluation of 27 probands (mean age 42±11 years, 82% males) with RLCM (repetitive VAs and ringlike scar pattern on CMR) and 62 asymptomatic relatives was performed Pathogenic or likely pathogenic arrhythmogenic cardiomyopathy mutations were identified in 11 (40%) probands, typically involving FLNC (15%), DSP (35%) and DES (20%) genes. Among the screened relatives, a total of 28 (45%) mutation carriers were identified, and 30 (48%) had evidence of LV scar at CMR, which had a ringlike pattern in 9 (31%) (all ≥30-year old). LV dysfunction (LVEF≤50%) and ECG abnormalities including inferolateral negative T waves and low QRS voltages were identified only among patients with ringlike scar in 6 (18%) and in 9 (24%) cases, respectively. Asymptomatic VAs were detected in 19 (31%) relatives, all with evidence of CMR scar. After a median follow-up of 5-years, no events were observed in patients without ringlike scar, while 12 (33%) of those with ringlike scar experienced a composite outcome of SCD/aborted SCD RLCM is a distinct familial form of arrhythmogenic cardiomyopathy characterized by high risk of malignant VAs and SCD. Systematic genetic evaluation of RLCM probands and cascade clinical/genetic screening of the family members detects pathogenic arrhythmogenic cardiomyopathy mutations and/or concealed cardiac structural abnormalities in nearly half of cases