In a study of 495 patients with cardiomyopathy, the infiltration of perforin-positive cells in the myocardium could serve as a predictor for long-term prognosis of patients; the presence of perforin-positive infiltration in myocardial cells indicates an adverse left ventricular ejection fraction (LVEF) course (Escher et al., 2014). The gene discussed is PRF1; the disease is cardiomyopathy.