Abstract 12885: A Challenging Case of Endocarditis— Multi-Disciplinary Approach is an Achievable Chimera

Abstract

A 60-year-old man with history of coronary artery bypass grafting and mitral valve repair presented with confusion, gait instability and lethargy. Cardiology was consulted after a transthoracic echocardiogram demonstrated a mobile mass on the mitral valve (MV). A subsequent transesophageal echocardiogram showed a large vegetation encompassing and adherent to the anterior annulus and leaflet. Serial blood cultures were negative. The initial differential considered causes of blood culture negative endocarditis (BCNE) with embolic phenomena to the central nervous system. This diagnosis was challenged after the patient developed progressive neurologic symptoms out of proportion to findings on brain imaging. A multidisciplinary team was established to revisit the available data and facilitate a coordinated care approach. The patient was found to fulfill 5 out of 8 criteria for hemophagocytic lymphohistiocytosis (HLH). Furthermore, an H-Score of 268 supported this diagnosis with a >99% probability. Therapy was started with Dexamethasone 5mg/m 2 BID and Anakinra 100mg Q6h, resulting in a rapid improvement in mental status. Secondary HLH in adults is most commonly due to malignancy and infection. Although initial workup was negative, several days into the hospital stay Mycobacterium chimaera was detected on next-generation sequencing of microbial cell-free DNA (Karius test). M. chimaera is a non-tuberculous mycobacterium belonging to the Mycobacterium avium complex and has been associated with a global outbreak following cardiothoracic surgery related to exposure to 3T heater-cooler units (HCU). Endocarditis due to M. chimaera acquired during prior cardiac surgery, complicated by HLH, was considered the most likely unifying diagnosis. This case illustrates: (1) the differential diagnosis of BCNE and the benefit of microbial cell-free DNA testing in its diagnosis, (2) HLH as an unrecognized entity in adults and infectious endocarditis as a possible trigger, (3) the need for improved awareness of M. chimaera infection in patients who have been exposed to HCU presenting with compatible symptoms, and (4) the critical role of communication and a multidisciplinary approach to provide high-quality care in challenging cases such as this one.