Conclusion:
We present a case of a young male with a newly diagnosed isolated JUP gene mutation and a genetically diagnosed family history of ARVC. During his course, he demonstrated the progression of a characteristic epsilon wave on ECG and the presence of new, atypical, left ventricular fibrosis on repeat CMR imaging. This case demonstrates a complex interplay between variable genetic penetrance, phenotypical heterogeneity, and lifestyle factors including exercise, in his disease expression and provides insight on the natural course of an isolated JUP mutation. Although rare, clinicians should have a high threshold for the suspicion of ARVC or variants of this disorder even in the absence of classic right sided pathologies and /or an initially normal work-up.