Abstract Body (Do not enter title and authors here): Introduction:
Sarcoidosis is a granulomatous disease that can affect multiple organ systems, including the heart. Cardiac Sarcoidosis (CS) is one of the most severe manifestations. It is characterized by a dysregulated T-cell driven immune response which generates non-necrotic inflammatory granulomas with myocardial infiltration. CS has a range of clinical syndromes: impaired conduction, arrhythmias, heart failure, and sudden cardiac death. We discuss a rare presentation of CS as an intra-atrial septal mass.

Case Description:
A 27-year-old Caucasian female with history of depression on citalopram presented with a one-month history of palpitations, fatigue, and dyspnea with exertion. An EKG demonstrated sinus rhythm with first-degree AV block. A cardiac monitor revealed intermittent 2-1 AV block and high degree AV block occurring mostly during sleep. An echocardiogram revealed normal biventricular function and morphology. Due to the concern for infiltrative cardiomyopathy, she underwent a cMRI which revealed a focal mass centered along the intra-atrial septum extending from the fossa ovalis to the septal AV junction, measuring 4.5 cm in size. She underwent pacemaker implantation with mild improvement of symptoms. PET scan demonstrated hypermetabolic activity of the intra-atrial region. She underwent surgical resection of the cardiac mass. Pathology was significant for fibrotic tissue with non-caseating granuloma and multinucleated giant cells consistent with an extremely rare presentation of CS. She was started on immunosuppressive medications. Subsequent cMRI and PET demonstrated resolution of the mass and hypermetabolic activity.

Discussion:
CS is a severe condition that most commonly presents with symptoms of heart failure, conduction abnormalities, and cardiac morphological changes of hypertrophy or thinning. However, it is often missed as a diagnosis, even in patients with extracardiac sarcoidosis. It is rare for CS to present as an isolated cardiac mass, especially in a younger patient as in this case. Advances in imaging techniques such as echocardiography, MRI, and PET have improved the ability to diagnosis CS and provide timely specialized treatment. This case highlights the need to include CS as an important diagnosis on the differential for a patient presenting with conduction abnormalities, heart block, and dyspnea. It also accentuates the critical role of multimodality imaging in working up this disease.