We report the case of a 41-year-old man with a diagnosis of sporadic arrhythmogenic right ventricular cardiomyopathy (ARVC). Genetic screening identified the heterozygous missense mutation R49H in the desmoglein-2 gene. The mutation was absent in both parents, and we demonstrated that it was a de novo mutation. To the best of our knowledge, this is the first description of a de novo mutation in ARVC. This has important implications, including for clinical practice, since individuals with sporadic ARVC caused by a de novo mutation can transmit the disease gene to 50% of their offspring. This suggests that the benefit of molecular genetics can be extended to sporadic ARVC and may improve genetic counselling.