Oligogenic cardiomyopathy.

Dr. McKenna and colleagues interpret the histology figure to diagnose cor adiposum in family member III-4 who died suddenly and was found to have extensive fibro-adiposis of the right ventricle[1]. The authors apparently made their diagnosis indicating that fibrosis is necessary for the diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC). We had described the histological data as “fibro-fatty infiltration of the right ventricle, encompassing 50% to 80% of the right ventricular wall thickness”[1]. However, we had not included specific staining for myocardial fibrosis. We provide Masson trichrome-stained myocardial sections, which show unequivocal evidence of myocardial fibrosis along with the excess adipocytes [Figure 1]. We also note that individual III-4 had pathogenic and likely pathogenic variants (PVs/LPVs) in the PKP2 and DSP genes, which are well-established causes of ARVC. Furthermore, cor adiposum does not exclusively and extensively involve the right ventricle, as observed in individual III-4, without involving the left ventricle. Thus, the data firmly refutes the diagnosis of cor adiposum and confirms the diagnosis of the classic ARVC.