Knowledge of rare but important clinical disease symptoms in cardiology is of vital importance in the daily routine as severe courses of disease as well as death may be prevented by early diagnosis, effective monitoring and timely initiation of an adequate therapy. In this article an important rhythmological disease, arrhythmogenic right ventricular cardiomyopathy, as well as two significant structural diseases, takotsubo (stress-related) cardiomyopathy and aortic aneurysm related to Marfan syndrome, as well as their implications for clinical practice will be presented.