Purpose of StudyCase.Methods UsedDescriptive.Summary of ResultsA 59 year old man with a history of lymphadenopathy, presented with shortness of breath and pleuritic chest pain since three days. A hyperpigmented maculopapular rash with urticaria was present along with multiple syncopal episodes and chronic diarrhea. CT scan of the abdomen in 2006 revealed lymphadenopathy, hepatosplenomegaly, and osteosclerosis. Inguinal and cervical lymph node biopsies in 2006 and 2012, and two bone marrow biopsies in 2012 were negative for malignancy. In 2009, he was diagnosed with non-ischemic cardiomyopathy with an ejection fraction of 40%. Peripheral blood, lymph node, and bone marrow flow cytometry were also unrevealing. On admission, the eosinophil count on admission was 500/µL. Echocardiography showed a large pericardial effusion with impaired right ventricular filling and significant respiratory variation in transmitral flow velocity. A pericardial window was placed, with drainage of approximately 1 liter of exudative fluid. During the surgery, the patient suffered sudden hypotension requiring epinephrine infusion. Tryptase levels drawn were 115 and 154 ng/ml. Pericardial tissue showed scattered c-Kit+ and CD25+ mast cells and blood PCR showed D816V mutation in the c-KIT gene. Re-stained stomach biopsy specimens from 2006 showed two clusters of c-Kit+ and CD25+ mast cells. A bone marrow biopsy showed aggregates of c-Kit+, tryptase+, CD25+ mast cells consistent with Systemic Mastocytosis. The transient hypotension was likely due to distributive shock from mast cell degranulation. Hyperactive mast cells may have served as mediators of the inflammatory response, contributing to production of the pericardial effusion leading to tamponade.ConclusionsSM with tamponade.Abstract P5 Figure 1