Systemic mastocytosis presenting as cardiac tamponade with CD25(+) pericardial mast cells.

In this first-in-literature case, we describe a patient with Systemic mastocytosis presenting with life-threatening cardiac tamponade associated with the presence of aberrant mast cells in the pericardium. Procedures involving surgical incisions through the pericardium in such cases can lead to uncontrolled mast cell degranulation leading to circulatory collapse.