Genetic Findings of Cardiac Sarcoidosis in a Case of Apical Variant Hypertrophic Cardiomyopathy with Recurrent Ventricular Tachyarrhythmias

Background: Genetic sequencing is changing the way physicians practice medicine. Hypertrophic cardiomyopathy (HCM) is one of the most common inheritable cardiac diseases. Sarcoidosis is a multisystem disease involving granulomatous infiltration of the lungs, heart, and other organs thought to be caused by a dysregulated immune system, influenced by genetic factors. Here, we present a case where an individual initially diagnosed with HCM was experiencing frequent episodes of ventricular tachycardia (VT). Further workup, including advanced imaging along with whole genome screening (WGS), revealed an unlikely diagnosis of concurrent cardiac sarcoidosis (CS). Clinical History: A 62-year-old man had ventricular fibrillation with workup notable for an ECG with deeply inverted T-waves, normal coronary angiography, and an echocardiogram and MRI showing apical HCM. An ICD was placed. Six years later, he had VT requiring a shock and was started on sotalol. He has now developed recurrent exercise-induced VT. While VT is seen HCM, the increasing frequency prompted further evaluation. A CT coronary angiogram showed normal coronaries and mediastinal lymphadenopathy. Lymph node biopsy revealed noncaseating granulomas and a PET/CT revealed hypermetabolic basal myocardium meeting HRS criteria for CS. Given minimal apical FDG uptake and a low likelihood that he had CS for 9 years without significant fibrosis, he likely has both HCM and CS. Using WGS, four genetic variants previously described in CS and HCM were identified confirming this diagnosis, HLA-DRB1, HLA-DQA1, ALPK3, and TTN. Discussion: HLA-DRB1 and HLA-DQA1 are both major histocompatibility complexes associated with CS. ALPK3 encodes alpha kinase 3 while TTN encodes titin. Truncating variants of ALPK3 are associated with HCM while pathogenic TTN variants have been described to cause HCM, DCM, and ARVC. This case reflects the potential of WGS in aiding clinicians in confirming an unlikely diagnosis.