Kocher-Debre-Semelaigne (KDS) syndrome is a rare form of hypothyroid myopathy, with associated hypertrophy of muscles.Although cardiac manifestations of hypothyroidism are well known, Desk reports of cardiac involvement in KDS have only described the occurrence of pericardial effusion as an association.This report describes an adolescent male presenting with typical features of this rare syndrome along with arrhythmogenic right ventricular STOP SMOKING HELP cardiomyopathy/dysplasia (ARVC/D), an association not yet described in the literature.