Abstract 11937: Genetic Cardiomyopathies Misdiagnosed as Isolated Cardiac Sarcoidosis: High-Yield Results of a Systematic Screening Strategy

Introduction: Isolated cardiac sarcoidosis (ICS) poses a diagnostic challenge due to its patchy myocardial involvement and low yield of endomyocardial biopsy (EMB). The diagnosis is often suggested by (18)F-fluorodeoxyglucose (FDG) avidity on positron emission tomograpy (PET) scan. Genetic cardiomyopathies (some of which may be FDG-avid) often present with similar clinical manifestations as ICS, so we evaluated a systematic screening strategy in which all patients with suspected ICS were offered genetic testing. Methods: We reviewed all patients in our Multi-Disciplinary Sarcoid Consortium for those given a diagnosis of ICS by the referring provider based on FDG-PET scans with myocardial but no systemic FDG avidity. These patients were offered genetic testing with commercially available genetic cardiomyopathy and arrhythmia panels (168 genes). Results: Of 110 patients referred, 16 met inclusion criteria, 1 had EMB-proven ICS, 1 did not consent, and 14 were referred for genetic testing. Ten patients (71%) also underwent cardiac MRI, of which 9 had late gadolinium enhancement. Mean age was 61.7±11.6 years, 12 (86%) were male. Mean ejection fraction at time of presentation was 43±10%. Four patients (29%) had presented with atrio-ventricular block, 12 (86%) with ventricular arrhythmias and 12 (86%) with left ventricular systolic dysfunction. Eight (57%) had EMB without granulomas (6 had not undergone EMB). Of these 14 patients, 5 (36%) had pathogenic mutations: 2 in LMNA, 2 in TPM1, and 1 in MYBPC3 . All 5 patients’ clinical phenotype was consistent with their genotype and 3 had previously been immunosuppressed without clinical improvement or resolution of FDG avidity. Conclusions: Genetic cardiomyopathy is often misdiagnosed as “isolated cardiac sarcoid.” A screening strategy of genetic testing all patients with isolated myocardial FDG avidity on FDG-PET scans had a 36% yield for pathogenic mutations and should be considered as part of routine clinical care.