A 65-year-old patient A had a more typical presentation including respiratory distress, chest pain, ST-segment elevations on electrocardiogram (EKG), lymphopenia, elevated levels of inflammatory markers and cardiac troponin I. A 34-year-old patient B presented with shortness of breath and chest pain similar to patient A; however, she had isolated cardiac involvement with systolic dysfunction and an acute pericardial effusion causing tamponade physiology. Here, TNNI3 is linked to pericardial effusion.